Maintenance and Repairs

Following are some of the questions we're often asked about general maintenance and mechanical repairs on old Ford tractors.

Click on a topic below or just scroll down the page.

  • 12volt conversion
  • Hydraulic problems
  • 8N Wiring diagram
  • Engine stalling
  • Gear oil
  • Engine oil
  • Lead additives
  • Steering box lube
  • Rear axle seals
  • Front king pin
  • Tie rod removal
  • Brake spring removal
  • Fluid in tires
  • Low oil pressure
  • Pistons & sleeves
  • Steering box info
  • Rocker pin removal
  • Front distributor timing

  • Rebuilding a Sherman combination transmission

  • Rebuilding a Sherman Step-Up transmission

  • Repairing a Select-O-Speed trans input shaft

  • Troubleshooting Select-O-Speed trans problems

  • 4 speed transmission locked up - Stuck in 2 gears



  • Q: "How do I convert my 8N to a 12 volt system?"

    A: You would need to get a Delco alternator (internal regular type is the easiest), fabricate the brackets to mount it, get a wider pulley for the front of it, run new wire to hook it up, and get a resistor to drop the voltage to the coil. If you're not familiar with electrical systems, I would recommend buying the kit that is available for this. It would be a little more expensive, but you get all the parts you need and instructions, too. Kits are available from several sources. On the web, you can find them at Just8Ns . If you're a determined do-it-yourselfer, first pick up an alternator. Tell the parts counter guy it's for a '76 Chevy. GM used this same alternator on about all it's vehicles from the early '70's through the mid '80s. Fabricate some brackets to mount it. If you have the tools and ability to make brackets, you won't need to ask how. If you have to buy the brackets pre-made, you are probably not going to save any money and might as well buy the kit to start with.


    Typical installation on a front distributor 8N



    Typical installation on a side distributor 8N

    The next step is wiring. Looking at the back of the alternator, you'll see a threaded post connector sticking out. Along the top edge, just to the right of the post, you'll see two spade connectors pointing up. These are numbered "1" and "2", left to right. It's best to have the correct double connector pigtail to plug on to these spade connectors. You can snip one off at a salvage yard, or pick up a brand new one at the auto parts store for a couple of bucks. They have them on those red bubble pack cards with the HELP name. There will be a smaller black or brown wire on the pigtail that goes to connector "1" and a larger red wire that goes to connector "2". The larger red wire goes over to the left and connects to the rear post connector. Get a length of heavy red wire (12 gauge minimum) and attach it to the rear post connector also. Run this wire up to the junction block on the dash and connect it with the "hot" wire coming from the battery. Get a length of smaller black wire (14 or 16 gauge) and connect it to the small black or brown wire on the pigtail. Run it up to the dash. This is the exciter wire for the regulator inside the alternator. This will connect to the side of the ignition switch that is only "hot" when the switch is on, but it must connect through a resistor (side marker lamp) or a diode. If you leave this out, you'll turn off the ignition switch and your tractor will keep running. I have used diodes, and they work great for me. Side marker lamps sometimes work and sometimes don't. Run up to Radio Shack and get a diode that's reasonably heavy, at least one amp or more should do it. Wire it inline so that the arrow or ring painted around the end points to the alternator. There is one other option if you don't want to mess with a marker light or diode and it's the one I prefer. Get a universal ignition switch at the auto parts store that has an ACC (accessory) position as well as an ON position. Hook the exciter wire to the ACC terminal instead of the ON terminal and you're in business. No diodes or lights are necessary. Install the 12 volt battery, NEGATIVE ground. Install a new 12 volt coil. These are available for front distributors, too. If you're set on using the old 6 volt coil, you'll need a resistor installed inline to drop the voltage to the coil. I have used a Delco Remy ignition resistor number D-1106 on many conversions and it works great. If you have headlights, don't forget to replace the bulbs with 12 volt models. Six volt headlights running on 12 volts burn really bright for a really short time. That should be about it, you're ready go. Oh yeah, the fan belt seems too fat for the skinny little pulley on the alternator. Most of the time it will work ok, the belt just rides a little high on the pulley. If you've got an alternator/starter rebuilding shop in your area, they could fix you up with a wider pulley if you need it. And, don't pitch out your old generator. There's a market for those things.
    [Top of Page] [Home page]


    Q: "Why does my 8N run for a few minutes and then die?"

    A: This is a very common complaint among Ford owners, and it usually stems from one of two common problems. First is fuel. Dirt or crud in the fuel tank will clog up the the shut off valve under the tank. The tractor runs until it uses up the fuel in the carburetor and then runs out of gas. After sitting a few minutes, the fuel will dribble down and refill the carburetor bowl and the tractor will restart and run a few more minutes. Remove the fuel line at the carburetor and open the shut off valve. You should have a good flow of fuel coming out of the line. If you have only a slow dribble, or none at all, remove the shut off valve and bowl assembly and give it a good cleaning with compressed air. Then unscrew the brass inlet elbow from the carburetor and check the filter screen that is attached to the end of it. They get clogged up, too.
    If the fuel flow is good and the tractor still runs a while and dies, then you likely have the other common problem - the coil windings are shorting out from the heat build-up and you lose spark when the coil gets hot. When the coil cools off, you have spark again. You need a new coil. There are other possibilities such as a faulty ignition switch that can cause the problem, but they are not as common.
    [Top of Page] [Home page]


    Q: "How do you set the timing on a front mount distributor 8N?"

    A: This is a common question from new 9N-2N and early 8N owners. The front mount distributor engine has no external timing marks. Instead, the timing is set mechanically with the distributor out on the bench. The drive tang on the back end of the distributor is offset and it fits in an offset slot on the front of the camshaft, so you cannot get the distributor installed wrong. Here's a scan of the static timing method from the I&T FO-4 shop manual.



    This method will work fine, but once you've tried it you find out right away that holding the rulers and checking for the points opening and moving the plate to the correct position is nearly impossible to do without having 5 hands available. Some people make a plug to fit the bolt hole with a larger OD so you only need one ruler. This is still a hassle and you need at least 3 hands to get the job done. We have made a simple fixture that makes the job much easier. It consists of one piece of aluminum flat stock and 2 machined plugs to fit the bolt holes on the distributor housing.




    The flat stock is machined to have the slot in the correct location, same as it would be with the ruler method. The 2 bolts attach the flat stock to the plugs. The 2 holes on the distributor housing are different sizes, so when the plugs are machined to the correct size for a snug fit the fixture cannot be installed the wrong direction. Here it is installed on the distributor.




    The snug fit will allow the distributor to be held firmly in the correct position and it's rigid enough to clamp in your vise while you adjust the points plate to get the "just open" position you want. A continuity tester, ohm meter, or test light works better than eyeballing it.



    If you're not able to build something like this yourself (and many can't because of the machine work required) check with a friend who can do it or a local metalworking hobbyist who can make you one. It's well worth the trouble.
    [Top of Page] [Home page]


    Q: "What kind of gear oil should I use in the transmission?"

    A: Originally, the 8N used 90w (GL-1) gear oil for the transmission, rear gears and hydraulics common sump. Capacity is 5 gallons. Many people today recommend using Ford 134 oil. This usually works fine in the 8N and is not so stiff in cold weather. However, if your system tends to leak, or you have a lot of wear in the hydraulic system, you probably need the heavier oil to keep things working and slow the leakdown rate. I use 80w90 gear oil (GL-5) or 90w (GL-1) in mine, just because it always works fine for me. When draining the gear oil, be sure to remove all 3 drain plugs (one under the transmission, one under the hydraulic pump, and a 3/4" pipe plug under the rear differential).
    [Top of Page] [Home page]


    Q: "How do I lube the steering gear box?"

    A: The steering box uses 90 weight gear lube. Lots of people have tired of leaking seals and now fill the box with thick heavy gear oil or grease. If using grease I'd recommend a soft black Moly grease that will stay fluid and not pack away from the moving parts or dry out. John Deere corn head grease is also a popular replacement. Straight STP works well, too. The most common failure with the steering box is a lack of lube to the upper thrust bearing. On the early steering boxes this bearing is above the full level in the box. Later steering box designs correct that, but owners still neglected to keep the steering box full and upper thrust bearings continue to fail from lack of lube. Over filling with a free flowing grease seems to solve this problem.

    The early ('47-'48) 8N steering box had a 1/4" pipe plug on the upper right side of the box. It could also be filled by removing the nut that holds the steering wheel on and pouring the oil down the hollow steering shaft where it flowed out a cross drilled hole and over the upper bearing (very slow process).


    The improved steering box (after 1949 serial number 216989) had a 1/8" pipe plug on the upper left side of the box hidden under the dash suport bracket and was nearly impossible to access.


    The '50-'52 models could be filled through the upper right hand side bolt hole where the dash panel attaches to the steering box.


    After serial number 452913 a screw was added to the front side of the steering column between the dash and steering wheel to allow adding lube from there. This let the oil again flow over the upper thrust bearing on the way down (a good idea) the same way the early models did.


    [Top of Page] [Home page]


    Q: "Can I upgrade my '48 to use the newer style 8N steering box?"

    A: Yes, it bolts right on and it's a VERY worthwhile upgrade. The early style steering box was a poor design from the beginning. The 8N had only been in production a couple of years when Ford figured that out and upgraded to the better designed Spicer type steering box that was used for many years after. Add some age and wear to that poor early design and you've got a steering box that will never be able to fully eliminate the sloppiness in the front wheels.


    Late style 8N box --------- Early style 8N box

    To upgrade to the later style box you will need a steering box and both pitman arms. The early pitman arms don't fit the later box. You will also need to pick up a later model dash panel to match the steering box, or modify your old dash panel for the necessary clearance. Here's how the early dash panel needs to be modified for use with the later steering box.



    Lastly, one of the drag links (tie rods) is an inch longer than the other. On the early models the longer tie rod was on the right. On the later models the longer tie rod goes on the left side. Just pop them off and switch sides. When you're done you'll have a much better steering tractor.

    [Top of Page] [Home page]


    Q: "How do you replace rear axle seals?"

    A: Rear axle seals leaking gear lube onto the rear brake shoes and onto the wheel rim is very common on 8Ns, especially the early models before the added inner seal. The major causes of seal leakage are improper (loose) axle bearing preload and worn (loose) hubs on the axle shafts. Installing the correct number of shims to obtain proper bearing preload when replacing seals is critical, as is having good hubs. If your hubs were loose on the axles before, they will probably need replaced. Once the hubs get worn, they will no longer tighten against the taper splines on the axles and you'll never stop the leaks. I have very rarely had to replace an axle shaft - severe wear from loose hubs has always been in the hub itself and the harder axle shaft was still good. You may not be so lucky. Inspect the hubs and axle shafts closely for wear. If your hubs were tight on the axle and required some force to remove them, they are most likely ok. Replacing the seals is not too hard of a job if you're used to working on old rusty mechanical things and have some basic tools. Here's a short rundown. It's not meant to replace the I&T FO-4 shop manual for the 8N. You will need the manual on hand before you ever start replacing the seals. Refer to it as you go.

    Leaky rear seal
    A common sight, the oil soaked
    rear brake drum on an 8N

    If your tractor is a '48 or'49, you have just one outer seal. If you have a '50 - '52 you have an outer and an inner seal. You will need the (Ford part number) A8NN4248A retainer assembly. This is actually the outer seal. The seal is pressed into the retainer. You will need the 8N4284 gasket and the 8N4225 gasket. That's it, unless you have the '50 or later model in which case you will also need the 8N4233A inner seal. First, remove the retainer wires and loosen the hub center nuts about 1 turn. Rock the rear wheel from side to side. If the hub doesn't move on the axle, drive the tractor around for a few minutes. Do some figure 8's. Sometimes this will loosen the hub from the axle taper and save you from having to use a large puller. If they still don't appear to be loose on the axle, go ahead and remove the lug nuts and rear wheel. Remove the brake drum (the 4 flat head screws holding the drum to the hub can be a bear to remove if they're rusted in - and they usually are). Remove the brake shoes. Pull the hub off, if it's loose. If it's not, get a large 3 jaw puller or a special hub puller and start tightening. Make sure to leave the hub retaining nut on the axle but have it a couple of turns away from the hub. Without the nut, the hub can pop off suddenly and do some serious damage to your knee caps.

    Puller

    Put pressure on the puller and tap the hub. Some are really on there and I've even had to resort to heat from a torch to get them to pop loose. This is a good thing. If the hubs are tight they are nearly always still good. If the hubs are loose when you start they are most likely worn out already. Once it's off, remove the 6 bolts holding the retainer and seal assembly and pull it off. The brake shoe pivot plate will come off now. Remove the last 2 bolts from behind (tractor side) and pull the bearing retainer and backing plate and slide the axle out to get access to the inner seal ('50-'52). Remove and replace the inner seal.


    '50 - '52 inner seal
    The inner seal on the '50 - '52 models

    On early models, removing the backing plate and axle is somewhat unnecessary, but you should go this far anyway to reseal the area where grease can leak between the backing plate and axle housing flange and also make sure you have the right amount of shims to properly load the axle bearings.


    Disassembled
    Disassembled and ready to clean

    This is the time to inspect the axle bearing and cup for wear and to reset the axle bearing load. Make sure the bearing looks good, no pits in the cup or on the rollers. Make sure the backing plate, bearing retainer, and all shims and/or gaskets are clean. I select the shims needed to load the axle bearings to zero load. Zero is hard to describe. It's no bearing load and no end play. If you're not sure how many shims to use, follow the procedure in the shop manual to set the load. I think their procedure loads the bearings a little too tight, but it's worked ok for a lot of years, so who am I to question it. Zero load is desired, but if you're in doubt, a little too loose is better than too tight. Too tight will ruin the bearings. Too loose will let the seals leak again. Setting the axle bearing preload with the shims is a commonly misunderstood procedure. Remember you are adjusting the total preload for both axle bearings. The axles butt together in the center of the differential and have a tapered bearing on each outside end. The total number of shims determines the preload and each shim affects both axles equally. You're not setting each side, you're setting the total.

    A good hub to axle fit is critical to the repair because worn hubs are the biggest cause of leaking seals. Here's how the splines should fit between the hub and axle - flush with each other when the hub is seated tightly in place on the splines. If the axle splines protrude past the hub splines the hub is worn. If the axle splines protrude far enough the washer will bottom out and you cannot tighten the hub onto the axle. The hub will also rub on the center of the bearing retainer. In that case, the hub is definitely shot and must be replaced.



    Here's the inside end of an axle that had too few shims installed. The bearing load was too tight and the axles butted together too tightly in the center. Besides destroying the axle bearings, the butt ends got hot enough to melt and smear the steel. Don't load them too tight.



    Be sure to pack the axle bearing with grease before you reassemble if you have the later model with inner seal. Clean all parts in a good solvent.


    Cleaned up
    Cleaned up and ready to assemble

    Reassemble with some Permatex Ultra Blue silicone RTV on all flange faces and wherever grease could leak out. The Permatex No.2 non-hardening form-a-gasket works fine, too. Use sparingly. Too much sealer just oozes out all over and is wasted as well as being ugly and possibly screwing up the bearing load you just worked so hard to set.

    Flanges sealed
    Use sealer on all flange faces

    The 8N4284 cork gasket goes over the axle between the axle bearing and the hub. The 8N4225 cork gasket goes between the brake shoe pivot plate and the retainer/seal assembly. Use Ultra Blue there, too.

    Assembling
    Putting it back together with the proper load

    Inner cork seal Sealed up
    8N 4284 axle to hub cork seal installed Sealer on every shim and face

    I put a small bead of sealer around the axle shaft splines before sliding the hub back on to help keep the gear lube from leaking out the front side behind the nut. Wipe a little oil or grease on the inside lip of the new seal and around the seal diameter on the hub before the hub goes on. This keeps the seal from running dry on the hub and getting hot right away.

    Hub
    Installing the hub

    Put the hub on and tighten the nut to hold it. Put the new, dry brake shoes on, install the drum, put the rear tire back on and finish by tightening the hub retaining nut REAL tight and replacing the wire clip. Adjust the brakes, and you should be leak free and stopping on a dime for the next several years. Recheck the nut occasionally to be sure it stays tight.


    Back together
    Finished and ready for the brake drum and wheel

    [Top of Page] [Home page]


    Q: "How do I remove the front axle kingpin?"

    A: The front axle center pivot pin or "king pin" on the 2N, 8N, and NAA tractors wears badly over the years from a lack of lube. It also tends to become bonded tightly in place by rust, especially on the front side, which makes removing it very difficult. The trick to getting it out fairly easily is to break that rust bond loose. I start by soaking both ends of the pin with penetrating oil. Then, after removng the retaining bolt, I use a drift and a hefty hammer to rotate the front flange on the pin to one side. An air hammer works well, too.



    Once the rust breaks loose and it moves one direction, soak it with penetrating oil again and drive it the other direction.



    Add some more penetrating oil and repeat as many times as necessary until it moves freely. You can now use some suitable prying tools under the flange to work the pin out of the bore easily.

    [Top of Page] [Home page]


    Q: "How do I remove tie rod ends?"

    A: The tie rod or "draglink" ends on the N tractors have a tapered stud that goes in to the steering arm and hold them tightly in place even after the nut is removed. It takes some mechanical force to pop the stud loose from the taper. Generally, this is done with tie rod separator tool commonly called a "pickle fork". However, the pickle fork tends to destroy the boots on the tie rod ends and lots of times you will want to save those. Many years ago I picked up an old steel wedge that I believe was originally intended to split wood. This wedge fast became my favorite tool for removing tie rod ends from the tractors.



    I recommend loosening the nut about halfway and leaving it on the stud to prevent damage to the threads and keep the tie rod end in place after it's loose. In these photos the nut has been removed completely. Do that at your own risk. First, slide the wedge between the tractor housing and the stud end and tap it into place so it puts just a light pressure against the stud. The wedge will distribute the force over a large area of the housing so it won't be damaged. Then, place a large drift against the arm right next to the tie rod end. Give it a sharp rap with a hammer and the tie rod stud will pop right out.



    The front tie rod ends are done the same way over the axle extension. If you have the later style steering arms you might need to put a spacer under the wedge or use a thicker wedge. One sharp rap and they pop right out, too.



    This is a quick, simple method and there is no damage to the tie rod boots.

    [Top of Page] [Home page]


    Q: "How do I remove the brake springs?"

    A: These brake springs are hefty and are under a lot of tension. Don't fight it. Borrow or buy a simple brake spring tool. The one I use is a Snap-On "S" shaped tool that's used for one handed removal and installation of the springs.



    To remove the spring you insert the tab on the cup end under the spring hook with the cup over the end of the spring retainer. Rotate the tool so the tab lifts the spring hook onto the tool and tilt the back end of the tool downward to pop the spring off.



    The opposite end of the tool has a small curved claw type end. To install the spring, slide the spring hook onto the tool, angle it up and put the claw end onto the spring retainer, and lift the back end of the tool. The spring will slide right on to the retainer. There are numerous other type spring pliers and tools available, but this style is as simple and easy as it gets.

    [Top of Page] [Home page]


    Q: "How do I remove the 3pt top rocker pin?"

    A: People seem to have a terrible time getting the rocker pins or sleeves out, but I've never found it to be that difficult. The right tools make all the difference. The hollow sleeve that allows the use of the 8N486A pin is the easiest to remove. First remove the 8N486A pin and disconnect the rocker from the yoke and spring.



    We use a driver made to just fit the sleeve. It needs to be 2 pieces because the driver plug is larger than the access hole.



    Put the driver in place and whack it with a heavy hammer.




    Thats usually all it takes, just a few whacks and it's out.



    The solid pin can be much more challenging. It's a very tight fit, and is more stubborn than the hollow split pin. It comes out the same way, using the same method, but with a straight driver. An inexpensive pneumatic hammer will usually walk them right out with very little effort.



    [Top of Page] [Home page]


    Q: "Why is water leaking out of my rear tires?"

    A: This isn't actually water unless you live in a very warm climate. It's most likely a calcium chloride mixture that's heavy and won't freeze. It's also extremely corrosive and will destroy your rims if it's leaking inside the tire. Tires are filled to add weight for extra traction and as ballast for a loader. You can drain it out yourself, but getting it back in the tire is best left to a tire shop that has the necessary equipment to pump it in. When adding air to a filled tire or checking the pressure, always have the valve stem at the top (12 o'clock position). To see if your tires are filled, position the valve stem near the bottom and carefully let a little air out of the valve stem. If the tires are filled, you will see liquid come out. To find out how much liquid is in the tire, hold a screwdriver by the blade, put your ear to the top side of the tire, and use the screwdriver handle to lightly thump the side of the tire starting at the bottom and working you way up gradually. You will hear a distinct difference in the sound from the tire when you reach the top of the fluid level and move into the air space. With a little practice, you will be able to pinpoint the exact level of fluid in the tire. Tires should never be filled more than 2/3 full. More than that can cause instability on hillsides, etc. When removing a filled tire from the tractor be very careful. They're very heavy and when tipped can fall over and injure the person trying to handle it. Have a strong helper around when you take these off.
    [Top of Page] [Home page]


    Q: "I changed my oil and now I have no oil pressure."

    A: This can also happen when a tractor has been sitting for a long period of time without being started. It usually happens because the oil pump pickup tube has come loose or the gasket on the oil pump is bad and the pump is "sucking air" rather than pulling oil up from the sump. Badly worn gears in the oil pump can cause it, too. It's a sign that something in the oil pump area needs attention soon. The easiest way I've found to prime the pump and get it going again is to remove the oil pressure relief valve from the front of the engine. It is a 15/16" nut on the top front of the timing cover just below the water pump.

    Relief valve location

    Remove the nut and pull out the spring and valve poppet. Get a trigger type squirt oil can and put the nozzle in the hole that the valve poppet goes into. Squirt several shots of motor oil into the hole. This oil will run down into the top side of the oil pump and collect on the pump gears. This is usually enough to prime the pump. Replace the poppet and spring and nut and fire it up. You should get oil pressure back again. If not, or if your oil pressure suddenly dropped to zero while the engine was running, remove the oil drain plug and verify that the pump pickup tube is still intact. It could have broken off at the pump which is above the oil level in the pan.
    Q: "How much oil pressure should I have?"
    A: The relief valve spring is designed to hold the poppet on the seat until oil pressure is 35-45 psi (Yes, the poppet IS supposed to have that flat spot on it). The relief valve only sets the maximum pressure attainable and has no effect on raising a lower pressure unless the spring is weak or broken. If your engine is in good shape, you will see 35-40 psi, hot or cold, at anything over an idle. Pressure at idle will be about 25. The main cause of low oil pressure is worn crankshaft bearings (main and rod bearings) followed by worn gears in the oil pump. The first symptoms of wear are good oil pressure when cold that drops off when the engine is hot. This is a sign that the clearances have opened up in there and the oil that has thinned when hot can now rush through the bearings faster than the pump can pump it. Oil pressure seems to be a topic that's misunderstood by a lot of people and these questions show up a lot. Basically, to create oil pressure in the engine, the gear pump first moves the oil from the sump by pushing it up through the passages in the block and creating a flow. The resistance to this oil flow is what creates pressure. Like water flowing through a garden hose, there is flow but little or no pressure. Putting your thumb over the end of the hose makes a resistance to the flow which quickly builds pressure in the hose. In the engine, the close clearances at the crankshaft bearings create the resistance to the flow. The N series flathead engines are notorious for low oil pressure with age because the pump has very little excess volume (flow) capacity when the engine starts wearing out. The pump just can't keep up with the leakage from worn bearings or shafts (no thumb on the end of the hose) and worn pump gears. The pump gear length was increased in the later 8Ns which helped the volume somewhat, but it's still not enough as the engine wears. I've seen a lot of advice given that just a few PSI is plenty for these old engines. If a person has just a rough understanding of what the oil pressure does they will see right away that 5-10 PSI is not nearly enough for any engine to survive on. The three main areas in the N engine that depend on oil pressure to survive are the crankshaft main bearings, the rod bearings, and the camshaft bores. When new, the shaft (crank or cam) runs inside a slightly larger bore that is fed oil under pressure. The clearance around the shaft fills with pressurized oil and the shaft runs centered in that oil film and (in theory) never touches the outside of the bore. If this condition can be maintained the wear on the shaft and bore (bearing) is extremely slight, especially if the oil is kept clean. The fly in the ointment comes when the engine is stopped and the oil supply stops. The shaft then contacts the bottom of it's bore and rubs during startup until the oil pressure can center the shaft again. As the load on the engine increases, the amount of oil pressure required to keep the shaft floating in the center also increases. If the oil pressure is low, the shaft is not supported on the oil film and very rapid wear occurs. The quick and dirty drawing below shows an exaggerated crossection of oil film on a shaft that is being supported by the oil pressure and what happens when the pressure is too low.



    The engineer who designs these engines could tell you how much load on the engine would overcome the oil pressure or how much pressure is needed for it to work safely. I don't know any of those numbers, but I know 5-10 PSI is barely enough for idling with no load. As soon as the rpm is increased or any load is applied it's NOT enough. The photo below shows a lower bearing insert from an engine that had been running with low oil pressure. The insert has worn completely through the bearing material at the bottom position from the crankshaft rubbing on it.



    In addition, when pressure is low the crankshaft itself is also wearing badly and becoming out of round and the camshaft journals and it's bores are wearing, too. The more it wears, the lower the oil pressure gets and it spirals rapidly until something starts knocking or lets go completely. Running with low pressure seriously abuses the engine. Thicker oil or thickening additives like STP will help increase the oil pressure, but they are a short term fix. It is possible to have a faulty (worn) pump causing low oil pressure (not creating enough flow) even when bearing clearances in the engine are ok. It's also possible to have a good pump and badly worn bearings and crankshaft causing the low pressure. However, low oil pressure symptoms in a well used N tractor engine is almost always a combination of both. Rebuilding the engine so it again has the proper bearing clearances and pump gear clearances is the only true fix. We also hear about newly rebuilt engines that have low oil pressure. A proper rebuild of the engine and pump will result in a running oil pressure of 40-45 PSI cold and at least 35-40 PSI hot. If it's less, something wasn't done right during the rebuild, plain and simple. Camshaft journals and the cam bores in the block are often overlooked during rebuilds. Normally, excessive wear on the cam journals and bores is not an issue with N tractor engines. But if you do find one with excessive wear that requires the expensive machining job to fit the block with cam bearing inserts, you can bet that wear was caused by someone who thought 5 psi was enough and kept running the engine that way. Be sure to verify that your oil pressure gauge is reading accurately before you condemn the engine.
    [Top of Page] [Home page]


    Q: "I'm rebuilding the engine. Should I get 3 ring or 4 ring pistons?"

    A: Go with the 3 ring pistons. The 4 ring pistons which are touted to seal better actually have more drag (friction) which causes more heat and faster wear that would offset any gains from the extra ring.
    Q: "Which type sleeves do I have?"
    A: If your engine is serial number 8N433578 or later, you have the .090" wall thickness cast iron sleeves. All earlier engines could have either sleeve since many were rebored at overhaul time. The only way to know for sure is to disassemble the engine and take a look. I've heard that some suppliers of sleeve kits only sell the heavy wall sleeve and tell you that the older block must be rebored for the newer sleeve. This is not true. The .040" wall thickness sleeves are available and will still work fine in the older engines.
    Q: "How do I replace the sleeves?"
    A: There are numerous methods for removing and replacing the sleeves. Obviously, the easiest and safest way is to use a commercial sleeve puller set. Reverse the puller setup to install the new sleeves. Most machine shops that do engine rebuilds will have one, and it's usually a pretty reasonable price for them to do the sleeve R&R for you. You may be able to rent one, or you could make your own that will do the job. The .040" thin wall steel sleeves (commonly referred to as tin can sleeves) can be removed by using a tool to crush the sleeve inward away from the cylinder wall. This is a risky proposition however, as many cylinder walls have been damaged and even broken by people trying to wedge a screwdriver or other tool between the sleeve and cylinder. Another method that seems to work well on both types of sleeve is to run a bead of weld from top to bottom of the sleeve (not too hot!). As the weld cools it contracts the sleeve and you can usually slide them out by hand. Clean the bores of carbon and scratches but do not remove any stock or you could find your new sleeves are loose. Freezing the new sleeves (VERY cold) will contract the diameter and allow the sleeve to drop right in the bore. However, I've never had a lot of luck with freezing at home since the sleeves warm up by the time I get them from the freezer to the engine block. Usually, the sleeve will press in the bore by pushing it down by hand. Place a short length of 2x4 across the top of the sleeve and lean on it. Make sure the sleeves are starting into the bore straight! You can tap on the 2x4 lightly with a soft mallot but never hammer on the sleeve itself. If your sleeves are tight in the bores and won't push in, make a puller to pull them in. Get a piece of heavy flat stock that will span the top of the sleeve and another that will span the bottom of the engine block. Drill a 5/8" hole in the center of both pieces of stock. Use a length of 5/8" threaded rod and 2 nuts between the 2 pieces of stock to pull the sleeves in. The top of the sleeves should be flush with the top deck of the block when installed. The sleeves were intended to be a light press fit into the bores. If you find that one of your new sleeves is loose in the bore, try another sleeve. Don't assemble the engine with loose sleeves, call a machine shop and see what other options they can offer.
    [Top of Page] [Home page]


    Q: "Do I have to use non-detergent engine oil in my 8N?"

    A: No. Todays motor oils are far superior to what the manufacturers suggested 50 years ago. Use any good straight weight or multi-vis motor oil in your 8N and it will be just fine. Crankcase capacity is six quarts with filter.
    [Top of Page] [Home page]


    Q: "Do I need to add a lead substitute to my gas?"

    A: No. Lead substitutes are nothing but octane boosters, and with the 6.5 to 1 compression on the 8N, you certainly don't need high octane. The 8N valve seats are hardened inserts and will not be harmed by unleaded fuel at all.
    [Top of Page] [Home page]


    Q: "Where can I find a wiring diagram for my 8N?"

    A: Here's one -

    [Top of Page] [Home page]


    Q: "My hydraulic lift isn't working right."

    A. The 8N hydraulic system is simple yet elegant and works great when properly adjusted and maintained. It consists of a pto driven piston type pump with internal control valves and a lift cylinder connected to the rear lift arms. The control lever and quadrant moves the valve spools on the pump to control the lift. The most common complaints are addressed below. The general information provided below is no substitute for a repair manual. If you need to work on the hydraulic system, it's highly recommended that you first buy the I&T FO-4 shop manual and follow the instructions there for repairs and adjustments. It's also highly recommended that you change the hydraulic oil (gear oil) and keep it fresh and clean at all times. The oil sump holds 5 gallons that is shared with the transmission and rear end of the tractor. It has a tendency to accumulate moisture from condensation inside the gear cases and the water collects in the bottom of the sump where it is drawn directly into the hydraulic pump. In cold climates the water can freeze and break the chambers in the pump. You definitely don't want that to happen. If the oil looks milky, it's got water in it. Change it.
    Q. "My lift isn't working at all."
    A. If the lift won't raise at all, first make sure the pto is engaged and the pto shaft is turning as it should be. Make sure the oil level isn't low. If those two things check out ok turn off the engine and remove the right side access cover (the one with the dipstick) and slide your hand down along the control rod into the oil and feel the end of the rod where it goes into the control valve pivot. Make sure the rod is connected and that it is moving the control valve spools in and out as you move the lift control lever up and down. Other possibilities are a defective relief valve or a ruptured oil tube that goes from the pump base to the top cover. To check these, leave the side cover off and start the tractor. Have a fairly heavy weight or load on the lift arms. Raise the lift control lever and watch inside the cavity for oil spraying out in the area of the relief valve or from the side of the cavity where the tube is located. If no oil is spraying out anywhere, you could have a bad pump. Check the pump pressure as outlined in the I&T FO-4 manual.
    Q. "My lift only comes up half way then stops."
    A. This is a very common complaint and can almost always be attributed to a worn cam follower pin in the lift control linkage. Loosen the 4 bolts holding the quadrant control lever bracket to the top cover. Slide the quadrant bracket toward the rear of the tractor (bolt holes are elongated). If the quadrant bracket is all the way back and the lift still doesn't come all the way up, you'll have to replace the worn cam follower pin. Remove the top cover and place it bottom side up on the workbench.
    Cam follower pin A worn pin
    Cam follower pin location A badly worn pin

    Find the worn pin. Disassemble the control linkage until you can get the part with the worn pin out of there. Press or drive the worn pin out. Replace with the correct hardened dowel pin part number 374072S from Ford/New Holland. This is listed as a 5/16" x 7/8" dowel pin but it is actually .309" diameter not 5/16" (.3125"). Pressing or driving a common .3125" pin into the .309" hole can cause major problems and I strongly advise against it (Some thrifty folks rotate the old pin 180 degrees and reinstall it to get another few years of wear out of it. That usually works ok if you can't spare the two bucks for a new one). Reassemble the linkage and adjust as per the shop manual instructions. Many times you will find that simply replacing the worn pin will take care of the problem without any further adjustments, but you have to completely reassemble the tractor to find out if you are lucky or not. Before replacing the top cover, take the time to inspect everything else in there for wear or other problems. This is an excellent time to rebuild the lift cylinder also. See the next question.
    Q. "My lift drifts down when the pto stops."
    A. Leakdown is probably the most common complaint with the N tractors, but it's usually easy to fix. If you have an implement on the lift and it drifts down over a few minutes time after the tractor is shut off you have some leakage. If the implement drops as soon as you push the clutch pedal in, you have major leakage. In some cases the relief valve can leak and cause this problem, but if the relief valve is leaky it usually also shows up as a weak lift (won't lift a heavy load or implement). The control valve spools in the pump base can leak due to scoring in the bores but this is rare and generally not repairable except by a major pump rebuild. The most common cause of leakdown is worn lift cylinder piston rings. You can determine if the leakage is coming from the lift cylinder by removing the right side cover (the one with the dipstick) and starting the tractor. Have a fairly heavy weight or load on the lift arms. Raise the lift control lever and watch inside the cavity for oil leaking out from above in the area of the lift cylinder. If the cylinder is leaking, you will see it. If the relief valve is leaking you will see the oil bubbling up from the pump area. The N tractors originally had a piston with 3 cast iron rings to seal it. These rings are still available, inexpensive and will work just fine, but a small amount of leakdown is normal and is to be expected with them. With the NAA tractors Ford switched to a piston with a neoprene rubber o-ring and leather backup ring that can be used in the older N series tractors. This provides a much more positive seal to eliminate the small leakage from the cast iron rings. The NAA piston and seal will cost more to replace than just buying new cast iron rings. The determining factor in which way to go is the condition of the cylinder bore. Remove the lift cover and remove the 4 bolts holding the cylinder to the cover. You can remove the piston fron the cylinder by applying a little compressed air to the oil inlet hole in the cylinder. Don't use a high pressure or you'll blast the piston out of there like a rocket. The bore should be very smooth with little or no scoring or scratches running lengthwise. It can (and probably should) be lightly honed to a cleanup. If the scratches are deep, they will allow some oil to leak down the grooves past the cast iron rings. In this case the NAA seal will work better, but only for a short time. The scratches or grooves will chew into the new neoprene seal and it will leak worse than ever. If you have deep scratches and do not want to spend the money to replace the entire cylinder assembly you should use the cast iron rings and live with the small leakage. If the cylinder bore is in good shape or has only very faint scratches or grooves use the NAA piston and seal.
    Q. "My lift went up but now it won't go down."
    A. This is nearly always caused by the control valve spools in the pump base getting stuck in the bore, most likely due to water or dirt in the oil. Turn off the engine and remove the right side access cover (the one with the dipstick) and slide your hand down along the control rod into the oil and feel the end of the rod where it goes into the control valve pivot. Make sure the rod is connected and that it is moving the control valve spools in and out as you move the lift control lever up and down. Chances are, you will find that the valve pivot is stuck and not moving. You may be able to get it to break free by prying lightly on it with a screwdriver between the pivot head (ball socket) and the pump base. When it breaks free and starts working again, CHANGE THE OIL. If it's really stuck tight, you'll have to pull the pump and rebuild it.
    Q. "My lift works by itself but not with a heavy load on it."
    A. This could be severe leakage at the cylinder, a bad relief valve, or a badly worn pump. Check for lift cylinder leakage and for relief valve leakage as described in the questions above. If no major leakage is noted, then check the pump pressure as outlined in the FO-4 manual. A rebuild is probably in order.
    Q. "My hydraulic pump makes knocking noises under load."
    A. What you're hearing is the sound of cams/pistons in the pump banging together. When the pump is new you get a slight knocking as the lift reaches the set height. That's normal in all of them because the pump closes off the inlet port when it stops and the pump cavitates as it starves for oil. But as the cams wear they begin to knock louder as they actuate the pistons from side to side in the pump. The louder the knock, the more wear your pump has on it. It's generally not an immediate pressing problem. If the knock is faint you can probably put off repairs for quite a while. If it's knocking loudly you should buy a pump repair kit and do a rebuild before it quits all together. Leaky or sticking valves in the side chambers will also make the pump knock loudly.
    Q. "My lift is very jerky and erratic when raising."
    A. This is usually a sign of a defective or sticking valve in the pump. The pump piston pushes the oil out then pulls it back in as it returns. Time for a pump rebuild.
    [Top of Page] [Home page]


    Back to the Home page