Does 3 in lbs matter?

Discussion in 'Transmission & Driveline Topics' started by LT1 WS6, Aug 12, 2016.

  1. jthomas

    jthomas Veteran Member Lifetime Gold Member

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    How much shorter? That can definitely cause a vibration if you have too much of the front yoke shaft exposed.
     
  2. LT1 WS6

    LT1 WS6 Veteran Member

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    I need to measure to be sure. Maybe 1/2 inch. I still have plenty of engagement with the tailshaft
     
  3. CorkyE

    CorkyE Veteran Member Lifetime Gold Member

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    I fought what I thought was a drive line issue for a real long time. It went away when I put four new wheels and tires on. I had two of the original 5 spoke wheels with a slight warp. I called a couple wheel shops and they didn't want to work on them since the warpage was in the center. You can easily check this with a spray can on the floor, next to the wheel. Rotate the wheel and watch the distance between the can and wheel. I knew I had this problem but kept blowing it off as not being the cause of my vibration issue.

    If you're not in a big rush, and make it to N GA in a few months, my car is going on jack stands, I'm going to do disk brakes on the rear, and I'm no speedy Gonzales. You can try my wheels & tires, see if that's the problem.
     
  4. LT1 WS6

    LT1 WS6 Veteran Member

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    I appreciate the offer Corky. I'll let you know if I need the help.
     
  5. czizza

    czizza Veteran Member

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    I too have fought with a drive line issue for many years and could not find it. I replaced the tires, the rims, the rear bearings nothing worked. Here is the log of what was done:

    Had a 60 MPH vibration that you either had to drive slower or faster no enjoyment at that speed.

    1) Original setup was a 355 Small Block w/Turbo 350.
    2) Replaced Transmission with ST10 ... same issue
    3) Blew 355 replaced with 409 Small Block ... same issue.
    4) Blew ST10 at track and rear end ... rebuilt both ... same issue.
    5) Rebalanced Drive shaft twice ... same issue.
    6) Replaced rear tires Foose Rims and Tire combo ... same issue.
    7) Blew ST10 again but this time on high way :) really need to behave.
    8) So I then found a TKO500 with Driveshaft on Craigslist that came out of a 455 Oldsmobile ... adapted it and had the drive shaft shortened.

    NO Issues anymore.

    In summary the only differences.
    1) TKO 500 but I would not say that was the cure because I did swap to an ST10.
    2) The TKO sits about 3/4 inches to the left at the rear cross member so I loosened up the headers and shifted it without issue.
    3) The replacement driveshaft came from Denny's I believe that was cut to fit.

    I think your best bet is to check the location of the rear cross member and output shaft in relations to the tunnel ... mine was offset to the right but is now centered in the tunnel.

    --Or--

    Get a new drive shaft which should be done for safety reasons anyway.
     
  6. LT1 WS6

    LT1 WS6 Veteran Member

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    The front yoke shaft has 1-1/2 inches exposed. This is the machined part I'm referring to. The center of the cap of the yoke u joint, not driveshaft u joint, is 3-1/4 inches back. So about 1/2 to 3/4 inch more than normal I'd say.

    I decided to measure pinion angles again because I'm running out of ideas but I'm fairly convinced it's in the driveshaft show how. I found that I have too much delta at the u-joints. The front joint is about 5* difference from the yoke to the drive shaft. The rear is a little over 4* difference between the drive shaft and pinion. I must have read the angle gauge incorrectly previously as this is new information to me. I also need to get a digital gauge instead of the plastic swinging gauge to help prevent this from happening again in the future. So at this point I want to concentrate on getting the delta at the joints below 3* if I can. Since my rear end is higher than the transmission, I'm going to raise the transmission up with shims and see what I can get out of that alone.

    How does that sound?

    Thanks everyone
     
  7. Dave Nelson

    Dave Nelson Veteran Member

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    It could be not enough yoke engagement, there should only be 3/4- 1 in. exposed, this can cause a vibration, it happened on my old race car.
     
  8. LT1 WS6

    LT1 WS6 Veteran Member

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    I FIXED IT!!!!!!! It was so simple too. I can't believe I missed it multiple times. Oh well, such is life. The one u-joint strap was not holding the cap fully. As I mentioned earlier, I replaced the rear u-joint due to it having a little bit more play than I thought was correct. Turns out that play was the cap moving and I just didn't see it. I noticed it this time though. I took both straps out cleaned them and filed the flats down so that I was certain no burrs or slight deformation would keep it from bolting down fully. I put everything back and the play was greatly minimized because the cap was no longer moving. Took the car out and there's nothing but smoothness.

    I'm still planning for a new driveshaft since I need a longer one. As you mentioned Dave, I need 3/4 to 1 inch exposed. I'm planning to rebuild the transmission and replace the engine this year yet. I'll do the drive shaft then, too.

    Thank you all for the replies and suggestions.
     
  9. jthomas

    jthomas Veteran Member Lifetime Gold Member

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    That's great news. Good catch. Glad you found it!
     
  10. Dave Nelson

    Dave Nelson Veteran Member

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    Glad you found the problem.
     

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