By Rick Stivers

In my search for detailed techniques for rebuilding a T-90 I found there was very little information. I was able to find a local transmission guy that was able to answer some of my questions. I found the service manual to be woefully inadequate for my needs. So I bought a T-90 and practiced taking it apart and putting it back together again. I have practiced it about ten times and I feel somewhat qualified to pass on what I have learned. If you wish to follow these instructions you will need to manufacture the tools listed below. If you prefer to use the heavy grease method of assembling the cluster gear, the choice is yours. Just skip the instructions that require special tools and figure it out for yourself using an illustrated parts breakdown (IPB). I found that my hands are far too big do that type of work so I made these tools and I am providing you with that knowledge. I make no guarantees that these procedures will work for every T-90. You will have to use them at you own risk. It would be very beneficial to learn the names of all of the parts from an IPB. I also recommend that you keep your old parts and practice putting the transmission together a few times before you do the final rebuild. Good luck, I hope you have as much fun as I did.

As other people use these instructions and provide me with feedback I will post their comments here in red. Merl is my first guinea pig and has provided great feedback.

I can be reached for comments at rick48cj2a@aol.com

Merl wrote - My T90 rebuild is finally done, and I must say that it went along much easier than I had expected. I used Rick's rebuild guide and a blowup picture for part name reference, never even looked at the shop manual for instructions on the rebuild. Overall, I'll give Rick's manual a hearty recommendation. I'm doing this from memory so I hope I'm not leaving anything out, but here are the more notable points and observations that I encountered...

As for my original problem...

T-90 shifts easily into R & 1st, never grinds at all even while rolling. However, after getting warmed up 2nd and 3rd would grind unless I shifted really slowly. The main problem was the worn 3rd gear synchro riding up too high on the surface of the input shaft bevel. The rear face of the synchro was scored where it had been hitting the small teeth of the input gear. But the *cause* of this looked to be the two shims between the rear shoulder of the mainshaft and the bearing spacer. I don't see these type shims in the shop manual (early Universal Jeep) and Rick said he hadn't come across them either. They sit between the shoulder of the mainshaft and the bearing spacer. They are cupped a little so that the outside circumference points in toward the large sliding gear (1st/R). My transmission had two of these. My local parts guy, Leo, said that while not typically used they are used to adjust the mainshaft play. He said that the idea was to align the rear face of the bearing spacer with the rear face of the bearing adapter. When installed, you want the rear faces of these two pieces to be flush. Any misalignment should be on the side of not enough shims rather than too many. It seems that the inside ring of the rear bearing rests on that spacer. Too many shims between the shaft's shoulder and the spacer would cause the 3rd gear synchro to ride too close to the beveled input shaft all the time causing premature wear. That's my theory anyway. When I put it back together I did a test fit before I put the rear bearing on and decided to not put a shim back in there. Another theory I have about this is that the tighter than normal mainshaft was allowing the smooth 1st/R shift. Maybe a sort of automatic double-clutch thing happening in there.

Rick Grover has since submitted his comments to the mix. http://www.public.asu.edu/~grover/willys You will find them filtered throughout the document. Anybody else?

Special Tool Manufacture

1a. Tool A is manufactured using a 3/4" wooden dowel rod. Cut it to 6 7/8" long. If the dowel rod has a rough finish, it should be sanded smooth and the ends lightly rounded. I did this using a 2" long drywall screw mounted in my drill. I turned on the drill and screwed the screw into the end of the rod at soon at it snugged up the rod was spinning nicely. It made sanding it very easy.

Merl has suggested you check the fit of the rod in the case to make sure that it fits in the hole. Nothing worse than pounding it into the case and getting it stuck. This would certainly defeat the purpose of this tool.

Merl wrote - Make sure you test fit the dowel through the front and rear holes of the case prior to assembling the cluster gear, sanding was required in my case.

Merl wrote - Look for conduit labeled 3/4". You might have to buy a long piece, but its dirt cheap.

1b. Tool B is manufactured using a length of 1" diameter electrical conduit. Cut it to 2 3/4" long with a hacksaw. It must be cut straight and any burs removed.

Merl wrote - Exact measurement of the electrical conduit tools is not critical. Within 1/4" inch of Rick's measure is OK, but do make sure there are no burs on the end of the tool.

1c. Tool C is manufactured using a length of 1" diameter electrical conduit. Cut it to 1 7/8" long with a hacksaw. It must be cut straight and any burs removed.

1d. Tool D is manufactured using a length of 1" diameter electrical conduit. Cut it to 1" long with a hacksaw. It must be cut straight and any burs removed.

1e. Tool E is manufactured using a 3/4" wooden dowel rod. Cut it to 2" long. The dowel rod must be sanded to slightly less than 3/4" and will most likely be destroyed in this use. You could also make it from a piece of brass rod but I used the wooden dowel since I already had some left over.

6" long piece of 2" PVC pipe

Tin bean can (optional but handy if needed)

Set of 12 point 1/4" drive sockets (I’ve been told that some of the bolts are Allen headed instead)

Pair of flat bladed snap ring pliers

Wooden board (I used a 2" X 12" X 24" but size really didn’t matter much here)

Work bench (I tried to rebuild it on the floor of the basement but found the work bench easier.)

Freezer :-)

Small brass hammer (A small plastic mallet would probably work just as well)

If still attached to the transfer case you could possibly need two long thin wooden wedges 5" long, tapering down from 1" should do.

Disassembly

2a. If the transfer case has already been removed proceed to step 2c. Remove screws from transfer case rear cover. Or, if equipped with PTO or Warn OD remove screws and remove the PTO or OD from transfer case.

2b. Remove transfer case bottom cover. Remove cotter pin, nut and washer. If you have difficulty removing the nut you can wedge a wooden block between the transfer case mainshaft gear and the intermediate gear to lock them into position. Once the nut and washer are removed the main gear can be removed from the main shaft. If it sticks two thin wooden wedges can be tapped in between the rear bearing and main-gear to pop it loose.

2c. If the shift tower has been removed while removing the transmission proceed to step

2d. Shift the transmission into neutral, remove the six screws from the shift tower and remove it. To hold the mainshaft in place until removal is desired loop install the front two shift tower screws back into their holes. Loop a heavy piece of wire under and behind the second speed gear and tightly wrap it around each of the two screws.

2d. If the transfer case has been removed proceed to step 2e. Remove the transmission to transfer case screws and separate the transfer case from the transmission.

2e. Remove the three screws from the main drive gear bearing retainer. Remove the retainer, seal and gasket. Remove the two twelve point/socket head screws that hold the oil collector to the case. The oil collector can not be removed at this time so move it out of the way of the main drive gear as needed. Tap the main drive gear forward about 3/8".

2f. Remove the wire and screws from the case and mainshaft. Slide the clutch sleeve forward on the mainshaft. Slide the mainshaft backwards then lift it upward and out of the case through the rear opening.

Note: (T-90s using the large style locking plate may have the plate installed over the top of the rear bearing adapter. This will prevent the rear bearing adapter from being removed. If this the case on your T-90 you will need to remove the locking plate as described in 2g prior to removing the mainshaft. This may prove to be difficult due to the limited space for accessing the reverse idler gear shaft with the mainshaft installed. In this case brute force applied to the locking plate may be required.)

Merl wrote - Disassembly was easy, the hardest part was getting that locking plate out of the slots on the rear of the two shafts. As Rick mentioned, mine was inserted from the top down and I couldn't get the rear bearing adapter plate off without first removing this plate. I bunged up the plate really well and wound up getting a replacement for it.

2g. Using Tool A gently tap the countershaft toward the rear of the transmission. Then using a brass hammer also tap the idler gear shaft toward the rear of the case. Remove the locking plate. Using tool A drive the countershaft out of the cluster gear. Drop cluster gear into the bottom of the case.

Rick Grover added - When you say to drive the counter shaft out, it should be driven out the rear. The front hole is a few thousandths smaller that the back hole. Driving it out the front would be much harder and could stretch the front hole.

2h. Tap the main drive gear forward and out of the case. Collect the pilot bearings and put them aside. Remove the oil collector, countershaft cluster gear and thrust washers from the case. Using tool E drive the reverse idler gear shaft out the back of the case. This must be done from inside the case. Caution: do not attempt to drive the shaft into the case from the rear as this can damage the shaft and the case. Remove the reverse idler gear from the case.

2i. Remove the main bearing snap ring using flat edged snap ring pliers. Hold main drive gear by the bearing and gently tap the small end of the shaft onto a board until the bearing slides down and off the gear shaft. On disassembly #3 for me this technique failed to work properly. I used an old tin bean can as a bearing driver. I put a board on the bottom of the can and smacked it one time very hard with a hammer and it came right off.

Rick Grover wrote - An alternative to the bean can bearing driver is several taps with the brass hammer. Worked for me. :-)

2j. Slide the clutch sleeve off of the clutch hub, making sure not to drop the three synchronizer plates. Using flat edged snap ring pliers remove the clutch hub snap ring. Remove the clutch hub from the mainshaft. Warning - years of the clutch sleeve sliding on the clutch hub can cause very sharp edges to develop. Use caution when handling the sleeve and hub. Remove the synchronizer springs from the hub. Slide the rear blocking ring and second speed gear off of the mainshaft.

Merl has described a shim installed in this location on his mainshaft. My transmission did not have this shim and the parts listing does not show it. It seems these were installed to bring parts into proper tolerance. If you have this shim remove it now.

1. The main Drive Gear bearing should be replaced if the center wobbles in the cage. I recommend changing it anyway.

2. The front Bearing Washer should be replaced if bent or scored.

3. On the Main Drive Gear inspect the pilot bearing race for scoring and pitting. Inspect all oil passages to insure they are clear. The inside diameter can be checked by measuring the diameter of the pilot shaft on the Mainshaft adding this size to the twice the diameter of a new pilot needle bearing. The sum of these diameters should be within .001" of the inside diameter of the Main Drive Gear pilot bearing race. An easier way to check this is to install new bearings in the race and insert the mainshaft into the bearing. There should be virtually no wobble of the shafts. If this fit is loose it will cause the pilot bushing in the engine crankshaft to wear out quickly. Check the gear teeth and blocking ring teeth for signs of wear and breakage. The beveled surface the blocking ring rides on should be smooth and free of cracks or pits. If any of these items is damaged you should replace the Main Drive Gear.

4. Countershaft gear Oil Collector should be examined for cracks and dents. If damaged replace it. Many people recommend leaving this assembly out of the transmission, but I recommend against this. The Oil Collector retains oil around the front end of the Countershaft Cluster Gear. This feeds oil into the needle bearings. In the event that you ran low on oil the collector would continue to feed oil onto the bearings. The Oil Collector will also help to prevent the oil from foaming at high speeds.

5. The synchronizer blocking rings should be inspected for broken teeth and worn mating surfaces. The mating surfaces to the Main Drive Gear and Second Speed Gear should have small grooves machined into them and should be free of cracks and chips. If damaged replace them as set.

Merl wrote - Inspection was also easy, just so long as you know what these things are *supposed* to look like. For example, I stated that my synchros looked good...*wrong*. I made this assumption without actually making a side-by-side comparison to new synchros. Turns out that while my 2nd gear synchro was ok, the 3rd gear was badly worn. Take your mainshaft assembly completely apart and take a good close look at everything. With everything apart take your synchros and put them on the beveled edge of the 2nd speed gear and the input gear. If either the beveled edge of the gear is worn or the rear or inside of your synchro is worn replacement is needed. As Rick suggests, you might as well just go for new synchros, they're cheap.

6. The Clutch Sleeve should be inspected for cracks and pits. Inspect the inside splines for sharp edges and burs. These can be removed with a file or crocus cloth. After cleanup, it should still fit snugly on the clutch hub. If not replace it and the clutch hub.

   Rick Grover wrote - The burrs on the inside of the clutch slider were pretty bad on mine. I worried about them and whether or not to replace it, but finally did as you recommend, filed them off with a fine file and emery cloth.

7. The Clutch Hub should be inspected for sharp edges and burs on splines. Caution should be used when handling a used hub as it could have very sharp edges. Using a file or crocus cloth remove burs. Check fit on Mainshaft and inside the Clutch Sleeve for snug fit. If it does not fit both pieces snugly replace it.

8. The Second Speed Gear should be inspected for broken and worn teeth. Examine the blocking ring surface area for scoring. Check for snug fit on main shaft. If it does not fit properly or if teeth are damaged replace the gear.

9. 1^st/Reverse sliding gear will take severe abuse due to not having a 1^st/Reverse synchronizer. Examine for broken or excessively worn teeth. Rounded and shaved teeth can still be used but gears with broken teeth should be replaced. Check for snug fit on mainshaft. If not replace the gear.

10. The Rear Main Bearing should be replaced if the center hub fits loosely in the cage. I also recommend changing this one anyway.

11. Inspect the Mainshaft for cracks, chips and excess wear of the splines. Measure the mainshaft pilot shaft to determine if, with new roller bearings installed, it will be within .001" of the inside diameter of the Main Drive Gear. If not replace it. If this fit is loose it will cause excessive wear on the engine crankshaft pilot bushing.

12. The Countershaft Cluster Gear should be examined for cracks and broken teeth. Because the 1^st/Reverse gear rides well up onto the 1^st gear ring on the Countershaft cluster Gear, you can have as much as 3/8" of wear to the 1^st gear ring without affecting the gear's operation. Small chips and sharp edges should be dressed with a file. With new Countershaft Washers, and bearings installed, the cluster gear should have no wobble on the countershaft. If it does replace the Cluster Gear.

13. The Countershaft should fit very tightly into the case. These shafts are cheap so replace it.

14. The Reverse Idler Gear will have worn teeth. These should be dressed with a file to eliminate small chips or sharp edges that could be broken off and left inside the transmission. Check the fit of the Idler Shaft for wobble. If it doesn't fit well or is missing large sections of teeth it should be replaced.

15. The Reverse Idler Gear Shaft should be inspected for chips or wear grooves. Since these shafts are cheap, if you suspect the shaft is worn then replace it.

16. Case must be thoroughly cleaned and inspected for cracks, giving extra care to the bottom and around each case opening. Ensure the countershaft and reverse idler shaft fit very snugly into the case. Do not leave any old gasket material on the mating surfaces.

    Assembly

    Merl wrote - I have to *highly* recommend Rick's technique using the electrical conduit. After I cut the tool A, B, C, and D pieces and finally understood the way Rick's method works, I put newspaper on our kitchen table, got my 6 & 8 year old boys to count out 4 piles of 22 needle bearings each, gave them a cup of grease and let THEM put the thing together. Of course I supervised to make sure everything was going in the right order, but the fact that my 6 year old did most of the work should tell you how easy these tools make it (plus, my boys had a good time with the grease).

    4a. Install the Front bearing washer onto the main drive gear. This washer is a form fit washer and should be put on the shaft so that it will match the contour of the bearing. Install the main drive gear bearing onto the shaft with the snap ring slot forward. This bearing is a press fit to the shaft but I have found that it can be installed by hand with no force if the bearing is heated to about 100 degree f and the main drive gear is chilled in a freezer for about 1/2 hour. Grease the shaft before freezing. You must install the bearing onto the shaft in one quick motion or the bearing will contract around the shaft. Make sure the snap ring is forward or you will have to do it again. Install the snap ring using flat bladed snap ring pliers. You are done with the Main Drive Gear for now.

    Merl points out that you not only need to grease the shaft but that it is a good idea to apply a good coat of oil on both of these parts to prevent flash rust from condensation.

    Merl wrote - A note about the freezer/oven technique for putting the front bearing on the input shaft. My input shaft was brand new, no oil residue on it at all and I left it in the freezer overnight. This made mounting the bearing on the shaft VERY easy, but after

    putting the shaft/bearing down in the garage after assembly I got lots of condensation on the shaft and sheetmetal washer. This causes flash rust! I would highly recommend that you put a light coating of oil on the shaft prior to freezing, it should prevent the flash rust problem if you do this on a warm/humid day.

    4b. At each step that says "install" during the assembly of the Countershaft Cluster Gear use a liberal amount of grease. To assemble the Countershaft Cluster Gear assembly:

    1. Stand the cluster gear on large end and insert Tool A into the hole. Next install Tool B and Countershaft Spacer over Tool A in that order. Install one bearing washer over Tool A and then install 22 needle bearing into the space left between Tool A and the Cluster Gear shaft.

       Merl wrote - Make sure you grease the middle spacer...I forgot. But, I was able to put a little light oil in the lube hole in the middle of the gear so I didn't take it all back apart.

    2. Lay the cluster Gear on its side and while holding Tool A in place, push the needle bearings into the shaft using Tool C.

    3. Stand the Cluster gear onto its small end and remove Tool B. Install 2^nd bearing washer and 22 needle bearings.

    4. Lay the cluster Gear on its side and while holding Tool A in place, push the needle bearings into the shaft using Tool D.

    5. Stand the Cluster gear onto its large end and remove Tool C. Install 3^rd bearing washer and 22 needle bearings, followed by 4^th washer.

    6. Stand the Cluster gear onto its small end and remove Tool D (It may be necessary to insert tool B part of the way into the shaft to remove Tool D). Install 5th bearing washer and 22 needle bearings, followed by 6^th washer. This completes the assembly of the Countershaft Cluster Gear assembly.

    4c. Place thrust washers coated with assembly grease into position in the case. The large thrust washer goes to the front with the brass side toward the cluster gear. The smaller thrust washer goes to the rear with the brass side toward the cluster gear. On some T-90 transmissions there should also be a steel thrust washer installed behind the small brass thrust washer. Place the Countershaft Cluster Gear into the case with the large end to the front. It will just lay in the bottom for now.

    4d. Place the Oil Collector in position in the case. Do not install the screws at this time.

    4e. Install Main Drive Gear into case from the front.

    4f. Install countershaft through the cluster gear from the rear of the case. Make sure the slot that is cut into the shaft is at a 90-degree angle to the case hole for the Reverse Idler Gear Shaft. The cluster gear should have between .012" and .018" of clearance. This should be obtained using thrust washer shims.

    4g. Place reverse idler gear in position with the larger center hub boss pointing forward. Install Reverse Idler Gear Shaft from the rear of the case. Watch the position of the locking plate slot.

    If you have the shim identified by Merl and you wish to use it, install it on the mainshaft now.

    4h. Install the second speed gear onto the mainshaft with the blocking ring mating surface pointing forward. Place rear blocking ring on the second speed gear. Install synchronizer springs into the clutch hub. They should be installed in identical positions with one in the front and one in the rear. One end of each spring should fit into the same synchronizer slot. Slide clutch hub onto the mainshaft with the larger center hub boss pointed forward. Install clutch hub snap ring. Heavily grease the synchronizer plates and hold them in place while installing the clutch sleeve over the hub. There are three slots in the blocking ring that the synchronizer plates must fit into to install.

    4i. Stand T-90 onto its front end with the main drive gear shaft hanging over the edge of the work bench. Insert Tool A into the pilot bearing hole of main drive gear. Grease needle bearings and insert them into the main drive gear. Remove Tool A.

    4j. Install rear bearing in rear bearing adapter and install snap ring. This bearing is also a press fit and the freezer technique mentioned earlier will work.

    4k. Place T-90 back down flat. Slide main drive gear as far forward as possible. Slide clutch sleeve as far forward as possible without releasing the synchronizer plates. Install front blocking plate with grease to hold in place. Install mainshaft from the rear of the case and insert into the pilot bearings.

    4l. Slide main drive gear back into case until outside snap ring is firmly against the case. Install screws in the Countershaft Cluster Gear Oil Collector. Install front bearing retainer gasket and bearing retainer oil seal. Install bearing retainer and tighten screws.

    4m. install 1^st/reverse gear onto the mainshaft with the groove forward.

    4n. Install rear bearing spacer on mainshaft. Install rear bearing adapter with the bearing onto the mainshaft. This is also a press fit but the freezer technique will not work here unless you put the entire T-90 into the freezer. J I used a 2" piece of the PVC pipe to drive the bearing down onto the shaft. The mainshaft washer and nut may be placed on the mainshaft for safekeeping.

    Merl wrote - The only other problem I had during assembly was getting the rear bearing pressed onto the mainshaft prior to inserting the mainshaft into the case. I tried Rick's 2" PVC pipe technique, but it tends to shoot small shards of plastic off into the bearing.

    I wound up using a blunt nose chisel on the inner race, a tap on the chisel with a hammer at 90 degree increments around the bearing race did the trick. It should be noted at this point that even though Merl had success using a steel punch to drive the bearing on, this is not a recommended practice. On occasion I have been known to hammer steel on steel. Sometimes this has met with success but on occasion I have had less than positive results. Rick’s recommendation below should be followed.

    Rick Grover pointed out - Brass hammer taps worked for me in place of the PVC pipe. (I love that brass hammer!) When I did my T-90, I never hit anything with steel. Get a brass hammer and/or a brass punch. They are about $10 each. They get all dinged up and even shed little brass flakes sometimes, but they do not scratch or mark the machined steel surfaces. It should also be noted that even a brass hammer can also damage fragile steel parts. I failed to follow Merl’s "Never hammer on the treaded end on anything" advise thinking that I could do so safely with a brass hammer. Wrong, I now have a perfectly useless output shaft for a Model 20 transfer case.

    4o. Install the countershaft and reverse idler gear shaft lock plate. Tap shaft into case to hold the lock plate in place.

    4p. Position the clutch sleeve and 1^st/Reverse gear into the neutral position. Place shift tower gasket in position and install the shift tower housing with the shift forks in the shift grooves. Install the six screws and tighten.

    Note: the shift tower is usually removed and installed in the vehicle. If you are just putting the shift tower on for safe keeping do not tighten the screws. This could damage the gasket.

    Merl wrote: Oh, and one last thing. While you've got your transmission output gear off (you've got to have it off to separate your TC and transmission), count the number of teeth on that sucker. You never know when you're going to run across a used Warn OD at a decent price and wouldn't you just HATE to miss out because you didn't know or guessed wrong?