Yoke Length

Discussion in 'Transmission & Driveline Topics' started by garyt30, Jan 11, 2019.

  1. garyt30

    garyt30 Veteran Member

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    I have a 79 Z with a Super T10 transmission. I've had some rattling issues when taking off easy which I eventually found to be where the wheels were bouncing around in the back like a basketball causing my leaf springs and everything else to move.

    I had a shop look at it and they are saying that the driveshaft yoke is too short and is causing this. It appears to have the stock size of 6 1/2 inch. The car has a 12 bolt rear end and I have no idea if this is even the right size driveshaft.

    Questions are:
    1. Would a short yoke cause this take off issue which really seemed to me to be like clutch shudder.
    2. Would getting a longer Yoke work or should I look at a longer driveshaft?

    Thanks in advance!
     
  2. badazz81z28

    badazz81z28 Veteran Member

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    How much chrome is sticking out of the tailshaft? I would look into a proper length driveshaft
     
  3. garyt30

    garyt30 Veteran Member

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    I just briefly looked at it but I'm not sure. Maybe 2 - 3 inches. Shop said that if the drive shaft was just an inch longer it would be fine.
     
    Last edited: Jan 11, 2019
  4. cadillac_al

    cadillac_al Veteran Member

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    You say the wheels are bouncing like a basketball huh? I can't see the yoke causing that. A regular length yoke should be fine. My Camaro has always been shaky taking off easy. I always thought it was clutch chatter. Changed clutch and surfaced flywheel and didn't change much. I never had the opportunity to look at my wheels on take off. I was told my chatter is probably the front leaf spring bushings. It kinda makes sense although my car has low miles. It sounds like that may be your problem though if the leaf springs are moving.
     
  5. cadillac_al

    cadillac_al Veteran Member

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    2-3 inches is a little much. You may have an issue there. I still don't know if it would cause wheel hop.
     
  6. Yellow69RSZ

    Yellow69RSZ New Member

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    Either way the driveshaft should only be back from being all the way forward by about 1 to 1.5" when the car sets on the ground. If you disconnect the rear u joint, shove it all the way in the trans and pull it out 1 to 1.5" the rear ujoint should be in the rear end yoke. If it doesnt reach, measure the gap and have the shaft lengthened. If that doesnt resolve the problem, look for other obvious issues. Best of luck!
     
  7. garyt30

    garyt30 Veteran Member

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    I have a new clutch kit and new fly wheel and rebuilt motor. No issue for about the first 150 miles and then it started rattling. I thought it was my exhaust until I had a friend watching it and then I saw it. Transmission was leaking in the front but I had a seal replaced to fix that but was told nothing was on the clutch itself.
     
  8. garyt30

    garyt30 Veteran Member

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    One other note is that the shop put on a used yoke they had that was probably like 3 inches longer but we think it was bad because the car had a bad vibration once I got moving. I didn't feel the wheels doing their bounce when I took off but didn't really drive it very long due to the vibration.

    I'm thinking of trying to see if I can get a yoke that is just an inch longer. I'm just not experienced enough to know if that would cause any other problems such as the vibration at speed.

    if that doesn't work then maybe I should focus on the leaf springs to see if that is the issue at take off.

    That wheel bounce at take off is when letting the clutch out. Happened in reverse too.
     
  9. dave@ztech

    dave@ztech Veteran Member Lifetime Gold Member

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    Or really bad shocks
     
  10. badazz81z28

    badazz81z28 Veteran Member

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    Going off memory here the 12 bolt if it’s an OEM 70 12 bolt, it used a 1310 u joint and the snout is shorter, so if you are still using the stock 79 driveshaft, it’s too short. The yoke is fine, start with getting the proper length driveshaft then move on from there. I agree, 1-1.5” is about normal with leafs.

    Also because the u joints are different from 70 to 79 (3r-1310), make sure you have the right ones installed
     

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