Swap long tail shaft to short tail shaft th400

Discussion in 'The "Juice Box"' started by silly, Sep 24, 2019.

  1. silly

    silly Well-Known Member

    I got a question. I have a 69 grand prix with the 400 tranny..The current tranny only goes in reverse so im gonna swap it out with another one but my tranny a short tail and i have one with 220,000 miles on it that was rebuilt 5 years ago out of a 70 skylark and it a 400 also but the other day my friend pulled a 455 olds motor out of a 98 with only 48,000 original miles and gave me the tranny which is also a 400 but it a long tail..Now i have a tranny jack and have done tranny swaps by myself before so i wonder cant i swap the tail housing from the short tail to the long tail to make it a short tail for my Grand Prix so i wont have to change the drive shaft to fit the long tail..is it possible for a novice like me or it cant be done? Im going have the bad 400 tranny rebuilt maybe next year but in the mean time want to install a new one asap..
  2. BrunoD

    BrunoD Looking for Fast Eddie

    I never done it myself,but my rebuilder has done it for me.Can you do it yourself?Get yourself a good book and try!.Easier then that,just shorten another driveshaft or your old one.Better yet,have your old trainy rebuilt.Bruno.
  3. Bens99gtp

    Bens99gtp Well-Known Member

    This is good news bad news for you. The good it can be done. 2 parts needs swapped, the extension housing of course, andvthe output shaft. The output shaft is only retained by a simple snap ring and is easy as pie to change...........once you get to it. Now the bad, to get to it you have to pull every single part out of the case basically to get to it.

    Now if not being rebuilt it requires pulling the valve body, front pump. All the drums and gear set out. I would guess a tranny shop, if not cleaning or checking anything, should be able to do the swap in under 1.5hrs.

    But unless you know the tranny is perfect it doesn't make since to not have thing thing checked when apart

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