T90 transmission

Discussion in 'General IH Tech' started by Scott80, Jul 3, 2019.


  1. Scott80

    Scott80 Farmall Cub

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    Recently rebuilt transfer case and transmission. Everything was moving and shifting properly before top was on.
    Test drive was great.
    Drove one mile, stopped for a bit and then started a longer run.2 .5 miles later I go to down shift from 3rd and it jammed up.
    Get the top off in a parking lot and photo is shown
    Clutch sliding 2 to 3rd gear is past the the middle of the keys
    Was able to push the keys back in place and pull the slider back to neutral. Put top on and stayed in 2nd whole way home
    Thought top rails were going bad so got a new top. 3rd gear gets jammed in a quarter mile. Coasted stop signs to get home
    Haven't pulled it off, not a happy camper.
    What's the reason it shifts too far forward past the middle bump on the keys?
    Do I have to pull all this out again or can I access main shaft by just sperating it from the transfer case?
    Thanks for any help
     

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  2. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    By "jammed up", do you mean it wouldn't shift out of third gear? If so, is it that the syncronizer clutch ring is stuck, or possibly the shift forks, rails and lever are the problem?
    Any more detailed information you can provide about either the rebuild or the problem? Who did the rebuild? If you, did you check endplay for the front shaft and between the front and rear shafts? What parts are new?
    I haven't worked on a three-speed for years, so forget what is or isn't possible to do wrong, such as mixing up shifting forks or putting one in backwards? Are both springs properly seated under the three syncronizer detent plates?
     
  3. Scott80

    Scott80 Farmall Cub

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    Wouldn't come out of third after driving steady for mile or so
    New top which has new forks
    Checked play for the transfer case with adding shims to get proper play
    Do not recall doing the same for transmission
    Added two photos from this morning.
    Tooth is gnarled up and the gap is significant with the screwdriver in it.
    Should it be much tighter?
    Front is even greater
    Update
    Front synchros can make full rotations left and right. Came out of spring?
     

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    Last edited: Jul 4, 2019
  4. Greg R

    Greg R Dreams of Cub Cadets

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    May we have year/model/drivetrain specifics? The 3 speed in the Scouts went through various changes. I believe the earlier ones there were a short and long tower for the top loader.

    Also, with the top loader off and the gear shift lever installed, how are the rails and detents? Easy and precise movement on the rails? Are the detents crisp and noticeable?
     
  5. Scott80

    Scott80 Farmall Cub

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    3 speed 62 scout 80 slant 4 with Dana 18
    Original loader failed
    New loader failed
    All components for the rebuild were new
     
  6. John Trumpe

    John Trumpe Farmall Cub

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    Hi, thought I'd jump in. I've built about 5- T90's including a '61 Scout T90. The picture with the screwdriver made me gasp. 3rd gear or input looks fine, but your main shaft has enormous endfloat. Are you sure you got the snap ring installed that holds the synchronizer assembly to the mainshaft? You will need to pull the transfercase and main shaft back out. Something is missing in the lineup to give that much endfloat. If you replaced the main bearing on the mainshaft, I'd compare the old with the new. I'd examine the parts diagram and see if something got left out. You need to measure the endfloat with the transfercase installed and the bull gear at the rear torqued up tight. In order for the brass blocking ring to rotate like you mentioned, the synchro pawls or "3 Plates" had to have the ends pulled clear of the square notches in the brass blocking rings. That would mean either the synchronizer assembly is loose on the shaft, or you missed installing the main shaft spacer by the rear bearing.

    When you remove the main shaft, do not drop the input large needle bearings out of the rear of 3rd gear. You can pull the mainshaft without pulling the transmission. The trick is going back together, you will need to shift the synchronizer into 3rd gear in order to clear the cluster gear and drop down in. There is a kit that comes with various main shaft shims that go next to the main shaft spacer to help set your endfloat. All has to be assembled to check endfloat. I use a magnetic mount dial gauge . You want basically no endfloat since just the rear main bearing will give .005. It must turn freely when tightened up. Even then, if you drive a few miles and come back and measure endfloat, you'll find it loosened up. I'd also buy a couple of magnetic drain plugs to catch any metal that comes off during break in. The metal is what kills all your work. Water is bad news also. John
     
  7. Scott80

    Scott80 Farmall Cub

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    J

    Thank you for the well written response

    I'm almost certain I have the snap ring on. Since Rick's video was taken off YouTube I found a young Canadian guy that has a great video. I followed all his instructions and checked and rechecked.
    I tried the magnet drain plug but the one I got was to tall and got chewed up by the gear. The gear sits really low

    I found Novak to have great parts and service I will try them for the shims
     
  8. John Trumpe

    John Trumpe Farmall Cub

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    I would suspect your mainshaft moves front to back the same distance that you gapped it with the screwdriver.
    Were your magnet drain plugs 1/2 inch NPT's with the flush flat, or round protruding magnet? I've just ordered the flat ones and will get them today. I have the Terra Flex Low 18's in two of my rigs and see that the larger intermediate gear is very close to the transfercase pan. It doesn't contact the stock drain plug.
     
  9. Scott80

    Scott80 Farmall Cub

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    I can not move the main shaft at all front to back
     
  10. John Trumpe

    John Trumpe Farmall Cub

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    Wow, you have something screwing with you big time. To have a gap like your last picture with the screwdriver between the blocking ring and 3rd gear drive dogs, either the main shaft is shifted rearwards, input shaft and bearing too far forward, or the synchro hub is too small. (wrong parts) . As hard as it was to get my pilot bearing to slip on to the input (2.5 hours and a helper) I feel for you having to take it back out. I'd investigate the parts on the main shaft from the synchro assembly rearwards first. Did your input shaft bearing have the big snap ring in the outer bearing race groove and the slider/nose fit cleanly and snugly to the front of the transmission case???? It isn't moving forward in other words?

    The rear bearing should have fit tightly in the pocket at the front of the transfercase and up against the rear large spacer at the rear of the transmission case. I've had different thickness mainshaft spacers cause end float between the inside rear bearing race and the shoulder on the mainshaft. That's where the shims in the kit fix you. The other thing is the sum of all the part heights. rear bearing inner race, mainshaft spacer, outside rear bearing race height and pocket depth, and gasket thickness. Lots going on. If you have extra parts, you can measure them and see differences. Snap rings included. Omix ada made a large front snapring for the groove in the front bearing that interfered with the slider/nose that bolts to the front. If you ever find a set of NOS made in the USA brass blocking rings, they are heaven. They shift so nice the difference is amazing. I hope you find this bugger. John
     
  11. Dana Strong

    Dana Strong Dreams of Cub Cadets

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    Was the transmission operated before its rebuild, and if so, how did it function then? What parts (complete list, please) were replaced? Do you still have the old parts to check for size, or to see if something old, like a spacer, didn't have a new component included in the kit? Because there were changes to the unit, and differences between the T13 (2WD) vs T14 (both w and w/o housing extension), closely following a video without being aware of those differences could allow for error. It's always best to document the existing assembly, comparing to a schematic while disassembling, or making sketches and labeling parts as removed, if one doesn't know the unit well already.
    Did this version have a large thrust washer between the front bearing and the front face of the drive gear on the input shaft? What about a thick steel spacer in front of the rear bearing? Something must be missing to give that amount of clearance.
    While you have the transmission apart again, it might be useful if you could get and post here the detailed specs. for the brass blocking rings: tooth count, internal and external diameters, front-to-back distances of both teeth and valleys, depth and width of the three grooves, and maybe even angle of front bevel. Also, any part numbers and/or name stamped on it. An engineering drawing to allow remanufacture, if someone here had the time...

    John; does this set look right to you? (w/o specs to confirm, of course):
     
  12. John Trumpe

    John Trumpe Farmall Cub

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    Dana, the NOS sets have "MADE IN USA" On the top flats. The last set I found were from Pete Debella. 90 bucks I think. I believe he is now out of them unless he found a rare new supply.

    Check out current ebay item # 183331153815. Brett Mullins in Tx. has the whole synchroniser assembly NOS for a T90 A or C found in M38 Jeeps. Same thing. I should buy one come to think of it. They say made in USA right on the brass blocking rings.
     
    Last edited: Jul 5, 2019
  13. Greg R

    Greg R Dreams of Cub Cadets

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    John, when I looked into 3 speeds years ago, Mike at MR Scout pointed out there were subtle differences through the years. One was the shift tower. I believe in 1963 they changed the gear shift fulcrum ball location and throw for easier shifting, a slightly longer shift to address complaints of popping out of gear mostly 3rd. That had a lower tower. 1965 were big changes in bearings and synchronizer rings to deal with higher horsepower, particularly the V8 Scouts. These are mostly seen in thicker blocker rings with wider dog slots; which are extremely rare. Most rebuilders, and Novak, are more familiar with the "regular" blocker rings and are more available as many Jeeps still use them. Not getting the right blocker rings in a 3 speed for a V8 Scout or late model IH 3 speed T14 has been the scourge of DIY rebuilders. Have you run across this?
     
  14. John Trumpe

    John Trumpe Farmall Cub

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    Hi Greg, I'm very familiar with Jeep T90's and T84's. My '61 Scout 80 and '62 parts running gear both had the T90 that are almost the same as the Jeeps. The input shaft and shifter cane shapes were different for the Scout . Jeeps had mostly T90 A-1's with some T90 C's which had different tooth count cluster gears, 2nd and 3rd. So, you need to compare and count teeth to get the right parts. The main shaft and synchronizer assemblies were the same between them and the early Scout 80. I am not familiar with the later Scout changes. Gear damage, and worn out parts are the same in both. The general operating parameters you need to achieve are also similar and if you don't get the clearances right, they self destruct or pop out of gear. Scott has way way too much clearance on both sides of his synchronzer assembly and I suspect he has the wrong parts in there. A few shims will not take up that much slop. Or-------a snap ring is off, missing, or spacer/bearing is wrong. He will need to compare his new with the old assuming the old were correct. I don't know what all was done etc. John
     
  15. Greg R

    Greg R Dreams of Cub Cadets

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    Thanks, John. I saw the same on the blocker rings too, but with no vintage or info on where or what I'm not inclined to comment other than yes, something is rotten in Denmark.
     
  16. Scott80

    Scott80 Farmall Cub

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    This spacer was in the used parts box from the rebuild.
    18. Spacer, mainshaft to rear bearing
    On the Novak diagram
    I have a rubber piece that has taken the shape of the spline. Do I need to back off the bearing, put the spacer and repress? Should I get a new bearing or can I use the old one?
     

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  17. John Trumpe

    John Trumpe Farmall Cub

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    Ok, the rubber thing is foreign. It may be off the bearing and used to be a sealed bearing, I don't know, but it should not be there. The sequence of assembly is: snap ring, Synchronizer assembly, and 2nd gear. All installed at the front of the mainshaft. Then from the rear: 1st/rev slider gear with the fork groove forward, main shaft spacer you have in your hand in the picture, (then if needed, shims to set the endfloat, large rear plate in the back of the transmission case, ( at this point you also need to install the small flat plate between the countershaft and idler shaft that keeps them from rotating) rear main bearing, gasket, transfercase, and finally from the back of the transfercase, the rear drive gear, washer, nut, and possibly a cotter pin. You have to torque the nut after bolting up the transfercase to tighten up the entire assembly. Then check the end float. I don't dope the gasket until I've set the endfloat or like things. Make sure you do not bolt the transfercase up with too long of bolts where they go through into the transmission or they will hit the gears. i use permatex #2 on the wet or threads that go into the transmission. Some rear bearings have that groove for a snap ring which is not used at the rear. The front bearing is narrower and does use a large snap ring in the groove. I always compare the old bearing sizes with the new to make sure they are correct.

    There should be a couple holes that are at the transmission fill plug level and holes in the gasket which drain excess oil that "worms" from the transfercase into the transmission back into the transfercase. Make sure the gasket is alligned hole wise. If not, it fills the transmission up too high and causes leaks out the front along the input shaft. WW2 t84 transmissions were notorious for this. You had to use totally sealed bearings and seal the rear gear splines to stop this. If you didn't you left a pool of gear oil everywhere you stopped.

    Remember you have to shift the synchro collar forward into 3rd to re-install the mainshaft. A wire wrapped behind 2nd gear and up to two of the shifter cover bolts will stop the mainshaft from falling out rearwards and dumping the large needle bearings into the bottom of the case.

    Another thing I do is smear permatex over the outside front of the clustergear shaft before I tighten it to the ball housing. It can cause a leak. Very irritating.

    If that spacer in your hand was not installed, I think you found your problem. John
     
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  18. John Trumpe

    John Trumpe Farmall Cub

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  19. John Trumpe

    John Trumpe Farmall Cub

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    Another tidbit or war story, I had a professional transmission shop build my T90 A1 for me He had a consulatation with another transmission shop. They decided to make a main shaft spacer to give me .020 endfloat. They did not use the original. Duh, it would not stay in 2nd gear and drove me nuts. So I did allot of research, and fixed the thing myself just like you are doing. I now strive to get as little end float as possible with the shims installed between the rear main bearing and mainshaft spacer. Some spacers are wider (longer) than others and the sum of all the stuff there makes allot of difference. No two are the same. End float is the number one cause of a transmission coming out of 2nd going down hill or letting off the gas in 2nd. So, spend some quality time and set that bugger up for nice free turning and very little end float. :wrenching:
     
  20. Scott80

    Scott80 Farmall Cub

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    Where do I find these shims, are they called shims for a trans or gonby another name?
    Thank you for the help on this

    Anyone rebuild tops? The replacement one I got is larger in diameter and doesn't even have the same bend on it
     

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