TH400 slip yoke on 1970 GS455 question(s)

Discussion in 'The "Juice Box"' started by gsgns4me, Jan 10, 2020.

  1. gsgns4me

    gsgns4me Well-Known Member

    I have been trying to solve a trans leak on my car. The leak is at the tail shaft area, mostly when the car sits this time of year.

    I have done the obvious things, twice. Those included replacing tail shaft seals, bushing, gasket, and the rubber o-ring on the tail shaft. Replaced speedo seals, then replaced the complete speedo housing with a new one. I've replaced the pan gasket.

    I have decided to replace the slip yoke, even though it seems to have a good fit in the new bushings. It's the only thing that isn't new on that end of the trans.

    I am having trouble figuring out which yoke is a correct replacement.

    Here is what I know about what I have as far as my yoke: my yoke is approx. 6.75 inches from u-joint center line to end of yoke, has 31/32 splines that are counter bored.

    My yoke still has the nylon locks in the grooves, so an internal locking u-joint 3R yoke would be correct.

    The problem is that nothing matches the length dimensions of my yoke. I know that I can use a hybrid set-up of internal and external locks for the yoke, but again I'm not finding the correct length measurements.

    I know the transmission is original to my car. I know the rear-end has been changed to an 8.5 inch. I don't know if the drive shaft is original to the car (has external lock on rear u-joint, tabbed pinion yoke). It may have came from the car the rear end was in.

    Any suggestions, part numbers, etc. for the correct slip yoke would be a big help. Thanks, and sorry for the long winded explanation.
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

  3. gsgns4me

    gsgns4me Well-Known Member

    Thanks, Larry. I'll have to take a look at it again. I know I have checked for a weep hole before, but I can't recall what I found.

    Would still like some thoughts on what yoke to use to replace mine.
  4. gsgns4me

    gsgns4me Well-Known Member

  5. buick64203

    buick64203 Just plum crazy Staff Member

    Just make sure theres no weep hole in the center of the yoke. Our cars dont need one. If there is one, the trans will dump out fluid if the car sits for a few days
  6. agetnt9

    agetnt9 Agetnt9 (Dan)

    Yep, leak is from back of yoke. clean and seal with high temp sealer of some sort.
  7. SoldierOfTheLaw

    SoldierOfTheLaw Well-Known Member

    Mine started leaking from that weep hole.

    I took the DS to a trans shop and they welded it shut.

    No more leak. Problem solved.
  8. gsgns4me

    gsgns4me Well-Known Member

    Thought I would follow up on this....

    No weep hole in my old yoke. No tell-tale fluid "spray" from the plug area of the yoke visible on the floor of the car. The leak was always right on the tail seal, soaking the mount area and most noticeable after being parked for a long period.

    I bought The Parts Place yoke (via eBay), some new Spicer u-joints (via Amazon), and picked up a new tail shaft seal & trans mount (ATF + rubber = bad).
    Took the car out weekend before last for about 20-25 miles. Has been parked for about 10 days now and no sign of a leak.

    The TPP yoke seemed like a quality piece.
  9. Bens99gtp

    Bens99gtp Well-Known Member

    If leak returns check the wiring around the electrical plug where it goes into the case........I had 1 leak from there I couldn't find till I replaced it with a other trabs as inthough the case was the issue

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