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Thread: T90 Reverse Idler Shaft Tear Down Controversy

  1. #1
    Super Moderator bmorgil's Avatar
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    T90 Reverse Idler Shaft Tear Down Controversy

    I am right in the middle of the T90 trans on my CJ3A. I have it torn down inspected and parts ordered. I used the Service Manual for Universal Jeep Vehicles as a guide. It was fairly straight forward nothing unusual. A LOT of water damage.

    The service manual page 168, indicates you "remove the reverse idler shaft by driving it into the case with a brass drift" A procedure I followed right down to the brass drift. I had no trouble. I drove the shaft out by completely driving it into the case and, removing it. All seems good.

    As I was looking for parts on the WWW, I noticed a tear down article on another web page. The writers stated to NEVER drive the reverse idler shaft into the case as it will damage the case and will not come out that way? I am not so sure. Is the service manual incorrect? I wonder if I damaged the case? I then read in more than one forum about persons having a very difficult time getting the reverse shaft out. All kinds of ideas on how to perform this difficult task. All focused on getting the shaft out via the outside of the case. I had zero trouble driving it into the case with a brass drift per the manual. What gives here? Can anyone shed a little light?
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    Last edited by bmorgil; 04-16-2019 at 06:46 PM.

  2. #2
    Super Moderator bmorgil's Avatar
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    Reverse Idler shaft update

    This was solved for me on another forum, there is wrong information out there. Imagine that!

    The T90 transmission does not use a tapered shaft in the reverse idler. It does not matter which way it is removed. I found it is MUCH easier to remove by driving it into the case as the manual indicates.

    The information not to drive the reverse shaft into the case, probably stems from the fact that several other Borg Warner transmissions do have tapered reverse shafts. These must be driven out in the correct direction.

  3. #3
    Super Moderator gmwillys's Avatar
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    Good deal. The transmission doesn't look too bad. It had a fair amount of water intrusion, but nothing that won't buff out. Are you going to put in the minor kit, or are you going to go ahead and perform the major?

  4. #4
    Super Moderator bmorgil's Avatar
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    T90 torn down

    It got a ton of water in the shift tower. Interestingly, it is the M38 style cover. Threaded on shifter cap. Some pic's below. Its getting the royal treatment. New main shaft, counter shaft, rev idler shaft, Synchro assembly in total, And a cluster gear. Bearings, small parts and gaskets. I was going to go through the cover it is in bad shape from rust. The forks aren't bad. I found a cover on eBay a NOS M38 cover covered in cosmoline for $70! The guy has a factory wire bin full of them. He must have 50 or more. Needless to say I tore down the old one for nothing.

    The failure analysis seems to point to water in the lube big time, through the shift tower. The second gear synchro surfaces on the gear and the clutch teeth on the collar, show that they were having trouble with second gear shifts. The main shaft is toast under second gear, probably wobbling all over. One sychro slider is MIA. The goop inside was so bad, it could have went through the gears. A sure sign that some one was leg shifting it into second gear.
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    Last edited by bmorgil; 04-18-2019 at 05:32 PM.

  5. #5
    Super Moderator bmorgil's Avatar
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    More pics of the T90
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  6. #6
    Super Moderator bmorgil's Avatar
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    And the last of the T90 tear down
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