T400 front yoke?

Discussion in 'Got gears?' started by rmstg2, Nov 2, 2012.

  1. rmstg2

    rmstg2 Gold Level Contributor

    How many size front yokes for the short T400. The yoke I have fits the output shaft spline but the outside diameter is smaller than the tail housing seal.

    Bob H.
  2. monzaz

    monzaz Jim

    ??? That is weird. I only know of one size 30-31 spline inner and all the same seal outer diameter. There are long yokes and short yokes and even yokes with dampeners on them. Jim
  3. GranSportSedan

    GranSportSedan Puppet dictator, wife has all power

    wasn't the 65- 67 sp400 a smaller outside diameter yet same inside spline count. in fact i'm sure it was, you had to change the tail housing on the trans if you wanted to use the larger yoke
  4. staged70

    staged70 RIP

    I am pretty sure my 4 spd is the bigger yoke like a th400 but is much thicker and I could be wrong here but it looks shorter than all my other BBB drive shafts (4) which are the same.
  5. DaWildcat

    DaWildcat Platinum Level Contributor

    Some of the '60's big cars used a smaller 1.688" diameter yoke. The driveshaft was a two-piece job with the slip fit in the middle near the carrier bearing rather than the slip at the tailshaft of the trans. Transmissions matched with a one-piece driveshaft usually use a larger 1.875" diameter yoke which is also a bit longer.

  6. BrunoD

    BrunoD Looking for Fast Eddie

    Maybe the yoke he has is from a 375 trainy?I think I have the tail shaft to fit the 400,and the opening for the yoke is smaller then the regular 400.BrunoD.
  7. DaWildcat

    DaWildcat Platinum Level Contributor

    The TH375 uses the TH350 yoke, the spline isn't common with the ST400 or TH400.

    For the big cars in the '60's, the extension housing is a smaller diameter because the yoke OD is likewise smaller, but the output shaft is still common among all 400's. Swapping output shaft housings to accommodate the yoke you want to use is pretty straightforward.

  8. rmstg2

    rmstg2 Gold Level Contributor

    I think you nailed it. The yoke i'm using is from a 67 Gran Sport I had way back when.:TU:

    Bob H.
  9. tburgeson

    tburgeson Roadmaster

    Yoke size is very a confusing subject. Does anyone know exactly what applications had the small ones and what had the large ones. I have a '65 trans in my hot rod that came out of an Electra with Super Wildcat option - large diameter. I have a '64 trans that is coded for a Super Wildcat engine - small diameter. I just picked up a '65 trans coded for a "regular" Wildcat - small diameter. I have a later THM400 from a '78 Electra - large diameter. The large diameter yokes seem to be rare piece. I won't even get into the ones with 'O' rings. None of mine had them. Yikes!!!
  10. monzaz

    monzaz Jim

    All 400TH trans should have 32 spline
    There are 2 different diameter that I know of 1.688 Early and 1.886 late
    Anything else I am unfamiliar with.

    Might be a better option to call up a tranny shop or drive shaft shop like Dennys. I am sure they would have the answer.
  11. lapham3@aol.com

    lapham3@aol.com Well-Known Member

    My big Buicks are centered around '66 and I concur with Devon's yoke size comment of 5 years ago. I've had an unmolested '66 Riv for many years that had a tailshaft area drip. With the E body x-frame it's not a joy to lube and evaluate anyway, so upon pulling the shaft to replace the rear seal, I found the o-ring that Tom mentioned. I also noticed a vent hole in the bottom of the yoke. It was a puzzle and strange to me. Anyway, I decided to just clean the area and epoxy the hole closed. After further inspection, I lubed and re-installed the shaft. The leak stopped and it's been fine for 20+ years. Also, many years ago my '66 Electra developed a take off shimmy and that was a bound up CV joint. I had a driveline shop replace it and the OE u-joints and all was well. It was a conventional yoke and did not have the o-ring arrangement. Dan Mpls. Mn.

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