TH400 yoke not going in all the way?

Discussion in 'Transmission & Driveline Topics' started by nuhmizer, Jul 24, 2006.

  1. nuhmizer

    nuhmizer Veteran Member

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    So I got my driveline back with a new yoke on it for my TH400. When I went to install it, I couldn't get the yoke to go into the trans all the way. Apparently, it should bottom out on the seal and it stops about 1" away from the seal. The guy who did the drive line assures me the yoke is the correct yoke for my trans (C tail housing). Anyone run across this before?
     
  2. insane4fbodys

    insane4fbodys Veteran Member

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    Yeap! The problem is in the tranny. Your tailshaft has a raised section that will not allow it to side anymore then it is. You can either get a shorter version yoke. (length wise) OR have a little more cut off the shaft and risk the yoke not being far enough in the tailhousing. Or opt for an aftermarket tranny that has the hardenshaft which doesn't have the offending raised section on the shaft.
     
  3. nuhmizer

    nuhmizer Veteran Member

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    I looked at the output shaft and can't find the raised section you're refering too. The inside of the yoke is bottoming out on the end of the tailshaft. The tailshaft hangs out about 5/8" from the end of the housing.
     
  4. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

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    insane is right,
    you have a truck output shaft and a passenger car slip yoke. It's bottoming out.

    You can get a counterbored yoke and it will work.
     
  5. 1WILDZ

    1WILDZ Veteran Member

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    I ran in to the same problem, I just had the yoke cut down, re-balance the shaft
     
  6. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

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    OK,
    I thought I remembered you posting about a TH400 yoke previously.

    Found it here:
    http://www.nastyz28.com/forum/showthread.php?t=57347&highlight=th400

    You have the pass car shaft, be sure the yoke isn't just catching on the oring.
    Also is the yoke vented? small hole in the end?

    It could be trapping air and cause it to not go in. If it is actually bottoming out, you'll have to shorten the driveline again.

    Measure twice, cut once.
     
  7. jakeshoe

    jakeshoe Veteran Member Lifetime Gold Member

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    If you converted from a TH350, you know you usually have to cut the driveshaft about an inch right?...
     
  8. nuhmizer

    nuhmizer Veteran Member

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    I measured from the pad on the rear yoke where the bolt goes in for the u-joint strap to the end of the output shaft (50") and then gave it to a driveline shop to shorten it. They also installed the yoke since the only one I had was from my TH350.
    Upon further investigation it looks like it's NOT bottoming out on the shaft like I said before.:eek:
    When I looked at the inside of the yoke at the splines, I noticed that there was one "double size" "female" spline. Is the yoke ment to only go on one way? Is there a tab or something that the double spline is supposed to slide over?
    This yoke doesn't have the relief hole.

    Also, what o-ring?

    Thanks for the help
     
  9. insane4fbodys

    insane4fbodys Veteran Member

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    The O-ring and the raised, which is really 1 and the same, section we are talking about can only be viewed by taking the tail shaft housing off. It's designed to prevent leaks out of the inside of the yoke. If you want to check for sure, jack the tranny up after unbolt the mount, take the mount off and then the tailshaft housing. You should see the raised portion and the cutout for the o-ring. Then with it off try and put the driveshaft in and see where it's actually binding up. I'm betting on the portion we have talked about. The best idea so for is to get the yoke designed for this appl. Good luck
     
  10. nuhmizer

    nuhmizer Veteran Member

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    here's my yoke. you can see the line on it from where the seal stops (grease). Correct me if I'm wrong, but isn't it supposed to go all the way in? I'm getting confused. If I have all the correct parts, why doesn't this work?
     
    Last edited: Aug 6, 2006

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