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Technical 1954 Chevy 3 speed not downshifting 3 to 2

Discussion in 'The Hokey Ass Message Board' started by clinkboat, Apr 18, 2018.

  1. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    I have a 1954 Bel Air with a 2nd design 3 speed. I rebuilt it with all NOS parts, including a new synchro drum and cones. It shifts up through the gears perfectly. When I try to downshift from 3 to 2, it grinds. I've tried double clutching and it just won't go into 2nd from 3 unless I'm almost stopped.

    I've measured and triple checked everything and it all seems to be working. The cones rotate in the synchros, the gears all turn and work properly. I've even tried shimming the energizing spring.

    I have 2 questions..1. What can cause it not to downshift when it upshifts perfectly? 2. Does the 2nd gear thrust washer have any other function besides as a washer between the bearing and 2nd gear?

    I am using 90w tractor gear oil with no synthetics...thanks for any help!
     
  2. F-ONE
    Joined: Mar 27, 2008
    Posts: 3,046

    F-ONE
    Member
    from Alabama

    Is the clutch fully engaged? For what ever reason it's easier to go up than go down. I know you have full clutch pedal but you may not have full clutch. You may just need more clutch or more.....cowbell.
     
  3. Boneyard51
    Joined: Dec 10, 2017
    Posts: 5,348

    Boneyard51
    Member

  4. saltflats
    Joined: Aug 14, 2007
    Posts: 11,037

    saltflats
    Member
    from Missouri

    Does it go into low gear fine when stopped?
     

  5. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Yes...or fully disengaged. It was replaced not too long ago....and I've checked it, adjusted it, etc.
     
  6. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Yes....it's like the synchro is not working on the 2nd gear side on the downshift. The forks are not worn, either.
     
  7. saltflats
    Joined: Aug 14, 2007
    Posts: 11,037

    saltflats
    Member
    from Missouri

    Was 2nd gear replaced also?
     
  8. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Yes...and it's the one with the flat spots for the 4 lug cones
     
  9. saltflats
    Joined: Aug 14, 2007
    Posts: 11,037

    saltflats
    Member
    from Missouri

    Did that gear rotate smooth and have free play?
     
  10. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Yes...
     
  11. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,283

    Kerrynzl
    Member

    It will upshift into 2nd from 1st means the 2-3 slider is in neutral then goes into 2nd.
    But downshifting from 3rd to 2nd means the 2-3 slider is in 3rd and wont go into 2nd.

    1st thing I'd check is bellhousing alignment.
    The input shaft is forced out of alignment and the blocker rings and slider hubs are initially not fully engaging on the 2nd gear dog rings.

    Have you tried the brute force "road racing" method of downshifting. Blip the throttle and whack it down fast. This should overcome bellhousing misalignment and confirm the issue [and improve ya skills:)]

    edit: Check the pressure plate on the clutch also. I've had them momentarily hang up [broken spring on one side]​
     
  12. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Good info....yes, my dad came over and did just that...which made me nervous with all the new gears! It still didn't work..just grinded. How do I check alignment?
     
  13. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    What exactly are blocker rings and slider hubs? The synchro cones?
     
  14. saltflats
    Joined: Aug 14, 2007
    Posts: 11,037

    saltflats
    Member
    from Missouri

    Sounds like when you are putting the heavy load on second gear is the problem.
    I would look at the thrust side of second gear and the cone as you call it that it has some tooth to the gear.
     
  15. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    The backside of the 2nd gear where the thrust washer sits against it, it wasn't very smooth...had some slight pitting. The old gear was super smooth and flat where the thrust washer ride against it.
     
  16. saltflats
    Joined: Aug 14, 2007
    Posts: 11,037

    saltflats
    Member
    from Missouri

    That sound's like it could be a problem.
    Did the gear feel rough when you side loaded it by hand on assembly onto the main shaft?
     
  17. F-ONE
    Joined: Mar 27, 2008
    Posts: 3,046

    F-ONE
    Member
    from Alabama

    Do you still have that gear? If it is usable, I would consider swapping it back if this is not resolved pretty quickly.
     
  18. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,283

    Kerrynzl
    Member

    Haha! I've always called them synchro rings until some American corrected me by saying they're called "Blocker rings"
    Sliders are what the shift forks move on a constant mesh transmission.

    Another thing is to pull the sliders out and de-burr them with a wet stone [or whet stone]

    To check the bellhousing alignment you will need to mount a dial test indicator to the flywheel and rotate the engine measuring run-out in the bell housing hole.
     
  19. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    That may be the next step...as well as checking the alignment of the bellhousing. It can't be off by very much, but could cause some banging. I'll have to replace that gear with another one. My original gear had a crack in it. Thanks for all of the help!
     
  20. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,023

    302GMC
    Member
    from Idaho

    Take the end play out of the top train. The snap ring groove for the rear bearing is the problem, being worn to the point the end play is too great for the syncro to work. At one time, selective fit 2nd gear thrust washers were sold, but good luck finding any today.
    Using a hard metal shim between the clutch gear & bearing to tighten things up will do it ... you have to estimate thickness.
     
  21. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,023

    302GMC
    Member
    from Idaho

    Not found in the Chev 3 speed - whole different trans ...
     
  22. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Got it..thanks. Any way to check for play...my bearing and snap ring is new...but you're saying the groove could be worn?
     
  23. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Now I'm questioning this...when you press the mainshaft into the case, isn't there a place where it stops...or do you just not press it in too far?
     
  24. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Or...does that not matter because the front u-joint yoke pull it the rest of the way when you bolt it onto the end of the output shaft?
     
  25. saltflats
    Joined: Aug 14, 2007
    Posts: 11,037

    saltflats
    Member
    from Missouri

    The yoke should have no effect.
     
  26. 302GMC
    Joined: Dec 15, 2005
    Posts: 7,023

    302GMC
    Member
    from Idaho

    The whole top train is held in place by the snap ring in the rear of the case. The yoke does, in this case, hold all of it tightly together. The problem with high milers driven hard - the wear is so great in the case, bearing, & snap ring that the play is greater than the range of syncro operation. To check end play, assemble the top train w/o the clutch gear & push it back & forth. Most of the torque tube 3 speeds will have .080 - .100 slop.
     
  27. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

     
  28. clinkboat
    Joined: Jul 9, 2008
    Posts: 39

    clinkboat
    Member
    from georgia

    Thanks....the bearings and snap rings have been replaced and I can't find any wear in the grooves. Even when I press the mainshaft into the case..there is almost no play. I am question in whether or not I pressed it in too far, not leaving the 2nd gear to spin freely. I tried adding a .10 shim under the energizing spring and had no luck. The onlty thing left is alignment, making the gear spin and hoping for the best!
     
  29. Kerrynzl
    Joined: Jun 20, 2010
    Posts: 2,283

    Kerrynzl
    Member

    read his 1st post
    "I've measured and triple checked everything and it all seems to be working. The cones rotate in the synchros, the gears all turn and work properly. I've even tried shimming the energizing spring"
     

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