T20 reassembly help

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Thread: T20 reassembly help

  1. #1
    Join Date
    Nov 2020
    Location
    Central Wisconsin
    Posts
    10

    T20 reassembly help

    Hello all,
    Working on my st400? Attex. I have another post asking for help identifying it. Anyways, this is a major overhaul project that i know very little history on.

    So i am cleaning everything up and getting rid of the 1/4" of caked on grease and dirt on the frame. Figured now would be a great time to tear apart the transmission and inspect internals.

    Unpon teardown, i saw that there were 0 thrust washers in the transmission. Only 2 metal washers that hold sun gears in place. I also Saw 2 bad bands (down to metal in spots). Should i replace all 4 bands? Or just the 2? I figure that the adjusters should allow me to run 1 new and 1 old on each side. Thoughts?

    Would prefer new if i have to get bands. Then i can send all 4 old ones out to be relined and have ready on my shelf. Plan is to replace the 2 other bands when i get about 30 hours on this rebuild.

    Now reassembly. Im watching a video that says to put in the first drum (after bands and what not). Then im supposed to put a thick thrust washer on top of that then the planetary plate that holds the planetary gears. I put in a shift lever and actuated that between Fwd Neut Rev to check alingment. Fwd and neut looked fine but rev looked wrong. Barely any engagement with gear teeth like thick thrust washer shouldn't be there. Take out washer and it looks good. Thoughts?

    Then i also have a question on thrust washers on either side of planetary gears. Video said early t20s (pre 1990) might have only had 1 thrust washer instead of 2. I put both in and set the rest of the parts in place to see if the metal washers interfered with putting last C clip on clutch side. C clip fit perfectly. Should i run both or just 1?

    I also had question on gap between center plate and housing. But read that if the clutch is on your bench, you can't go by the gap between housing and center plate. I plan on getting a manual soon for service n whatnot. Just looking for advice in the meantime.

    I appreciate the help. I have pictures to show what im talking about but need to figure out how to add them again.

  2. #2
    Join Date
    Nov 2020
    Location
    Central Wisconsin
    Posts
    10
    Sorry for the novel above. Here's some pictures hopefully. If you can't see them, please let me know.20210606_151350.jpg20210606_151421.jpg20210606_174226.jpg
    Last edited by TJ_6x6; 06-06-2021 at 07:01 PM. Reason: Pics not showing/im an idiot

  3. #3
    Join Date
    May 2010
    Location
    Fairbanks AK
    Posts
    1,456
    Early T20s had only 2 large fiber washers between the case and back of ring gear drum. If your ringgear drum requires a thick washer between drive plate there will be a machined pocket for it. The planet drum can be machined to accept the fiber washers on both sides of the planet gears. Post close up pic of inside of ring gear drum and pin side of planet drum.

  4. #4
    Join Date
    Nov 2020
    Location
    Central Wisconsin
    Posts
    10
    20210608_204609.jpg20210608_204636.jpg20210608_204652.jpg20210608_204747.jpg20210608_204752.jpg

    So i need to get my plate and planetary drum machined to accept the fiber washers? Or just recommendation?

  5. #5
    Join Date
    May 2010
    Location
    Fairbanks AK
    Posts
    1,456
    Your ring gear drum dosent accept the thick fiber washer. It’s ok just like it is. Is there any wear on planet drum where gears thrust next to pins? If they are worn in more than .010” I would press out the pins and ave them machined to accept the fiber washers. The drive plate dosent get machined. If Wippers video on updating the drums is still posted on this site check it out. I believe he gives proper dimensions to get proper end play when assembled. If you don’t find it I can get dimensions in couple days. They work fine but have a better life with the fiber washers. I suspect yours is a 74-76. Most of the ones I’ve had a good build date on had washers by 77.

  6. #6
    Join Date
    May 2010
    Location
    Fairbanks AK
    Posts
    1,456
    Your ring gear drum dosent accept the thick fiber washer. It’s ok just like it is. Is there any wear on planet drum where gears thrust next to pins? If they are worn in more than .010” I would press out the pins and ave them machined to accept the fiber washers. The drive plate dosent get machined. If Wippers video on updating the drums is still posted on this site check it out. I believe he gives proper dimensions to get proper end play when assembled. If you don’t find it I can get dimensions in couple days. They work fine but have a better life with the fiber washers. I suspect yours is a 74-76. Most of the ones I’ve had a good build date on had washers by 77.

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