M21 to M20 Swap - No Joy!

Discussion in 'U-shift em' started by knucklebusted, Mar 31, 2018.

  1. knucklebusted

    knucklebusted Well-Known Member

    Well, I thought this was going to be easy. Same case, setup and everything, just transfer parts over and done! Two hours tops, right?

    First, the trans cross member is rusted out on both sides. It was barely being held in there. Really need another one bad!

    Then I discovered the tail shaft bushing was shot in the M20. No big deal, pull the tail shaft of the M21 and use it. M21 tail shaft comes off easily, not the M20. Can't drive the pin out of the reverse shaft.

    I found a roller bearing in the drain pan while taking the rear seal out. Is this something that might have been in the M20?

    OK, let's find a bushing and seal locally. Luckily, the O'Reilly's showed one in stock. Went to get it. Some yahoo, bought it, stole the bushing and returned it. Only the seal was in the box!

    Defeated!
     

    Attached Files:

  2. crash

    crash Well-Known Member

    The roller in your fingers is one of the 17 rollers where the input and main shaft come together...

    Good luck... Crash
     
  3. gstewart

    gstewart Well-Known Member

    U could grind off the rust areas from the cross member and have someone weld extensions onto the ends. I had that done to my cross member many years ago. a friend of the family welded pieces of stainless onto the ends. i had to grind off the excess length. worked good.
     
  4. knucklebusted

    knucklebusted Well-Known Member

    I bought some ends from Mike Garrison. That's what I'm going to do.
     
  5. NZ GS 400

    NZ GS 400 Gold Level Contributor

    Paul Cangialosi has some great videos on his youtube channel for Muncie rebuild and repair. Those videos and his book helped me successfully rebuild my M21.

    Re: the reverse shaft pin.....make sure you are trying to drive it out from the bottom.
     
  6. knucklebusted

    knucklebusted Well-Known Member

    It was not in that area so I'm going to hope (maybe pray) it was from a rebuild as it came out of the tail shaft area when the seal was removed.

    I watched a bunch of his videos. I don't have the tools to do a full rebuild. Yes, we got the M21 pin out but the M20 pin is really stuck. I've got a bushing and seal on order so I'll just use it as is and deal with this problem if it arises in the future.
     
    Last edited: Apr 21, 2018
  7. NZ GS 400

    NZ GS 400 Gold Level Contributor

    If you go to Paul's website, you can email or call him. He could probably give you some tips on how to get that pin out. I talked with him myself briefly and he was very helpful.
     
  8. philbquick

    philbquick Founders Club Member

    You may want to fish around with a magnet and be sure there's no more loose rollers. I'd hate to see what would happen if one got into the gears, it would probably be loud!
     
  9. knucklebusted

    knucklebusted Well-Known Member

    This one was in the oil return area of the rear tail shaft, under the bushing and fell out when I took the rear seal out. I've stood it up on both ends and haven't seen or heard anything in there. Yes, it would be loud.
     
  10. crash

    crash Well-Known Member

    The bigger question, is one, or more missing from the input/main shaft...

    If its me, it comes apart before bad things happen...

    Hope this helps... Crash
     
    GranSportSedan likes this.
  11. 71gs3504sp

    71gs3504sp Well-Known Member

    Could always use a Cutlass transmission cross member and it just bolts to the frame. Looks just like the Buick cross member but it eliminates the rubber bushings.
     
    NZ GS 400 likes this.
  12. NZ GS 400

    NZ GS 400 Gold Level Contributor

    Great to know!
     
  13. hugger

    hugger Well-Known Member

    Those rollers are a PITA to get in there without them dropping, I was doing one years ago, couldn't get it, so I took it to a trans shop, he does it and a couple got somewhere they weren't supposed to be and it spun like rocks were in it at idle. So they will work but you need a full teardown and inspection
     
  14. BrianTrick

    BrianTrick Brian Trick

    980619D4-81C6-4978-8101-624D2966434F.jpeg Here is a picture of a Cutlass/442 crossmember. The one in the middle. These were used for all transmissions.
     
  15. knucklebusted

    knucklebusted Well-Known Member

    I'm going to try it like it is. Worst case scenario, I've still got the M21 to put back in and have the M20 rebuilt, maybe into an M23Z with the really low first gear.
     
  16. knucklebusted

    knucklebusted Well-Known Member

    Next "No Joy" moment is attempting to get a rear bushing for the large 32 spline M20. I've been given 4 different bushings and I finally started mic-ing them. The new ones are 1.99" and fall through the tail shaft. The one I can find online is 2.01" and should be correct. I try to buy local but I've spent more in gas than the bushing costs making trips to and from the place.

    FYI: National Seal 5208 is not correct. The proper bushing appears to be WT297-62 or GM 3978765 or 13941 AG.
     
  17. knucklebusted

    knucklebusted Well-Known Member

    Finally got the correct bushing, installed it and the seal is in. Crossing my fingers that it all goes back together nice and easy.
     

    Attached Files:

  18. knucklebusted

    knucklebusted Well-Known Member

    Finally, after 3 weeks me and a buddy got it back together. So many problems to overcome. First, the crossmember ends were rotted out. Second, the tailshaft bushing was wiped and the locals keep giving me the wrong part. Third, the pilot bushing pulled out of the end of the crank!

    Got new M20 in this morning, filled it full of GL-4 fluid, ran it through the gears on jack stands to listen for any odd sounds of impending failure. None detected so we put it on the ground and went for a test drive.

    I'm really loving the 2.52 first gear. It is like a completely different car! It doesn't feel like you are taking off in second gear all the time.

    Now, to see if it leaks after a test drive and now sitting on a clean spot in the garage.
     
    sriley531 and ap1672 like this.
  19. telriv

    telriv Founders Club Member

    Most ALL Muncie,s mark there territory
     
    300sbb_overkill likes this.
  20. CJay

    CJay Supercar owner Staff Member

    Both of mine leak from the countershaft. I think they leak from new!
     

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