This Page is the Installation of a Sherman Combination Transmission in my Ford 8N tractor.
These tractors are surprisingly easy to work on. The 8N can be split without removing the hood, which greatly reduces the number of items that need to be removed.
This is proof that a concrete floor isn't absolutely necessary even for major work like a from split. A solid piece of plywood or concrete floor certainly makes most jobs much easier.
1—Battery—Disconnect both cables and the hardware holding the battery in place, then slide the battery out. If there wasn't anything holding the battery in place put that on the list of things to buy.
2—Remove Both Footboards—I removed the two front carriage bolts that attach each footboard to the brackets. In the back it was easier to remove the entire bracket.
3—Remove Left Brake Rod—This is located beneath the left footboard. Remove the cotter pin between the front clevis and the side of the transmission. This is a little difficult to get at, and the pin was very reluctant to come out of the hole. Once the front end of the linkage was loose, rather than fight the same battle with the back end, I simply unscrewed the rod from the rear clevis bracket.
4—Intake Air Tube—I previously bought a chrome-plated aftermatket version of this part. It looked great but was difficult to install and I discovered it was nearly impossible to remove. After comparing the chrome part to my old tube, I realized the aftermarket tube was bent a little different. Lesson Learned— The original part is now back on the tractor. If I had no concience, I'd sell the chrome one on eBay. It hangs on the wall in my workshop as yet another reminder of money wasted.
5—Fuel Line—You could probably get away with just removing one end, but I removed both ends and set it aside where I knew it wouldn't get bent.
6—Choke and Accelerator Rods—these have spring-loaded ball-and-socket ends that you simply pull out while holding the rod and they should pop right off.
7—Starter Wire at the Start Pushbutton—Remove the rubber boot on the switch and remove the screw holding the wire to the terminal. Then pull it up and tape it to the dash or coil it in a safe place.
8—Tail Light Harness—Disconnect at a convenient spot. These have usually been rewired, so find a convienient spot. You may have to just cut the wire. Try to find a place that is in a concealed location so the new splice won't show or get rained on.
9—Radiator Cap—This could get pinched or scratch the hood when the steering box is raised, so it's best to remove it now.
10—Make Some Wedges—I cut two 6" pieces off the end of a 2x4. Then cut each of those on a diagonal so I had four 3-1/2 x 6" wedges.
11—IMPORTANT STEP!—Two of the wedges should be placed under the front axle center section. Put one on each side, right where the axle pivots on the engine. See photo above. The wedge is visible just beneath the bumper bracket. A Couple of medium whacks with a hammer should seat them in place. These wedges are to prevent the engine from pivoting side to side after the bellhousing bolts are removed.
12—Steering Box—Remove the bolts holding the steering box to the top of the transmission housing. Remove the two top bellhousing bolts that go through the battery bracket. Once those bolts are out, you should be able to pull up on the steering arms and break the housing loose. Once it is loose pull up and slide a wedge between the top of the engine and the battery tray to hold the steering box up high enough to clear the bellhousing flange. Photo above shows where I put the wedge to hold the steering box. It's just to the right of the air filter assembly.
Here is the tractor ready to be split. As you can see, I made a bracket for a trailer screw jack and attached it to the side of the transmission housing. A close-up of that item is next.
The bracket is a piece of 3" angle with holes drilled near the edge that line up with two of the bolt holes in the flange between the transmission housing and the rear end housing. You need a heavy duty jack, this one was rated for 750 lbs and was barely adequate.
Once you have everything supported, make sure the transmission is in neutral and start removing the rest of the bellhousing bolts. Watch to see if anything moves. If you get any misalignment of the two halves, fix it as the tractor comes apart. You might need to go up or down a bit on the jacks as the tractor splits to keep things level. A little adjustment here will make it a LOT easier to slide the two halves back together later.
Tractor is split. The floor jack is under there to steady it while I install the Sherman.
1—Once the tractor is split, remove the left brake pedal, remove and save the key that positions the brake pedal on the shaft, and then remove the brake cross shaft.
2—Measure for the location to put the hole for the shifter, 2-7/16 down from the top flange where the steering box mounts and 5-3/4" back from the back of the starter casting. These measurements should get the hole located within 1/8" or so of where it needs to be. Use a hole saw to cut a 1" hole. This is big enough to see exactly where the actual center of the hole needs to be after the Sherman has been installed. We will finish this hole out to 1-1/4" later.
3—Take a photo showing how the two springs and the throwout bearing are installed. Remove the springs and bearing assembly. If there is any question about the condition of the throwout bearing get a new one. Notice that the input shaft for the Sherman is a much shorter version of the transmission input shaft. Remove four bolts that hold the tractor transmission input shaft assembly in place. Pull the input shaft assembly out. Remove and gasket material that remains around the transmission input shaft flange area. Notice that the gear on the transmission input shaft matches the output gear on the Sherman. Now we can see how the Sherman does what it does. The Sherman replaces a solid input shaft with a small gearbox. Store the original input shaft assembly someplace safe where you can find it if you ever want to remove an auxiliary tranny and install the original input shaft parts. The input shaft also makes a much better clutch installation tool than any of the plastic things.
4—Remove the front input shaft and support assembly from the Sherman. BE CAREFUL! There is a thrust washer and bearing that go between the input shaft and the output shaft. Set the Sherman input assembly, thrust washer and bearing aside for now. Remove the Sherman rear mounting plate and gasket if they are attached to the main body of the Sherman.
5—Bolt the Sherman rear mounting plate to the front of the tractor transmission where the input shaft was bolted. Use at least 2 shims and one paper gasket. You will need a 5/16" Allen wrench or socket to tighten the bolts.
6—Now, jockey the main body of the Sherman into position, don't despair, it will fit. You just need to find exactly the right angle and facial expression or curse word and it will slide right into place.
7—Once you have it in there, put a gasket on the rear mounting plate and start each of the 4 mounting bolts by hand. Don't tighten anything yet, just get the bolts barely finger-tight.
9—Leggo of the Sherman and rest a bit, drink a beer, whatever.
10—Now the bad news. You will have to remove and reinstall the Sherman at least one more time. The reason we left the bolts loose before the rest break is that we need to feel for a very slight increase in effort to turn the transmission shaft as the Sherman mounting bolts are tightened. Get a socket and LONG extention bar to tighten the bolts. Make sure the tractor transmission is still in neutral. Frequently check the effort to turn the transmission shaft as the four bolts are gradually tightened. There once was a special tool available for reaching into the Sherman to turn the shaft. Most likely only tractor dealers had those. My fingers worked ok to reach in thru the Sherman and turn the shaft. If you feel more than a slight increase in effort or no increase in effort at all, the whole thing has to come back out to add or remove shims between the Sherman mounting plate and the front of the transmission. It is essential that this bearing preload be correct. The bearing preload is correct when a very slight increase is noted in the effort required to turn the shaft and very little play can be felt sideways. Slightly too loose is better than too tight. If additional metal shims are needed to get the correct preload they may still be available from New Holland dealers as part numbers:
If your parts guy cannot find the shims using those numbers, have him try these newer CNH part numbers:
If you have a parts tractor, an assortment of shims should be available behind the bearing caps of the transmission. The shims frequently appear on ebay with other transmission parts.
11—Once you have correctly guessed number/thichness of shims and the preload is right, YAY! NO, Stop Celebrating. It ain't done yet. Yep, once it's right, pull the Sherman back out again to apply a very thin smear of Permatex #2 sealer to the rear mating surfaces of the Sherman, the mounting plate, shims, gaskets, then reinstall everything properly torqued. Using too much sealer just makes a mess. Use only enough that the surfaces appear wet. Any more will only squish out and end up where you don't want excess gasket goo to be floating around. Make one final check of the bearing preload. By now you should be intimately familiar with what feels right when turning the transmission shaft.
1—Replace the thrust washer and needle bearing on the front end of the output shaft. Use a little dab of grease to hold it in place.
2—Pour about 2 pints of gear/hydraulic lube into the Sherman housing. Use the same stuff you put in the tractor sump. Don't skip this step! The Sherman should not be operated dry for the time it would take for splash to move enough fluid from the main sump. Wile operating the Sherman constantly exchanges fluid with the main sump.
3—Install the Sherman input shaft assembly to the main housing (use a thin swipe of Permatex on both sides of this gasket also).
4—Now, with the Sherman finally in-place we need to finish that hole we made for the shifter. The hole needs to be 1-1/4" in diameter and centered exactly on the shifter mounting point. A rotary die grinder with small pointed stones works well to mark and grind the outside diameter of the hole. Be careful not to grind on the shaft the shifter bolts to. Once the outside location of the hole has been formed enough to guide a hole saw the rest of the way, a 1-1/4" bi-metal hole saw can be used to quickly punch the diameter all the way thru. This requires using the hole saw without a pilot bit. Start slow and once the bit has started cutting it will not move around. Finally smooth the inside and outside edges with the grinder.
5—Clean-up the dust and chunks, install the rubber grommet, and bolt the shifter in place.
6—Turn the input shaft of the Sherman to be sure it's free. While turning the input shaft, shift the Sherman through it's gear positions to verify it is shifting correctly.
7—Install the brake cross shaft, key, and left brake pedal.
8—Install the throwout bearing and two return springs.
9—Remove any temporary supports and get the two halves of the tractor lined up. They must be completly level and square to each other. This is your last chance to inspect/replace clutch disk, flywheel ring gear, and starter for wear. Replacing a starter now is at least 100 times easier than when the tractor is back together.
8—Next time I do this I will make two dowel pins to help line things up. Get two long bolts that match the threads in the back of the engine, cut the heads off, and grind to a rounded point. Install these hand-tight on opposite sides of the bellhousing and use them to help align the two halves of the tractor. UPDATE: Once I made and started using those dowel pins alignment problems became no problem at all. Another slick trick is to look at the position of the clutch disk splines and pre-align the transmission shaft splines.
9—Roll the rear half forward and use a box-end wrench on one of the pressure plate bolts to turn the engine and align the input shaft splines with the clutch disk. Note: If the clutch and transmission shaft splines were carefully pre-aligned there no need to turn the engine.
10—The two halves should go together smoothly. Don't force it!! Figure out what the problem is and correct it. Start a few bolts in bellhousing. Do not use the bolts to force things together when something seems hung-up. The flanges should just bump together with little effort. Don't forget to knock the wedges out from between the front carrier and axle before taking a test-drive.
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