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Help/ driveline/ Diff

Discussion in 'The Garage' started by ssped, May 1, 2006.

  1. ssped

    ssped 1/2 ton status GMOTM Winner

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    I am getting a fluttering vibration when on the freeway and feathering the throttle on and off. I have summed it up that it is behind the Tcase(replaced that last week) I need help pinning it down.

    Here is the set up. 4" Ord shackle flip, 14b rear Axle, drivelines unlimited drive shaft, 6deg axle shims and Tcase drop(as far as it will go without the engine hitting the firewall).

    the drive line is 3" out on the yolk from the Tcase. My pinion and tcase angles match. I did notice that the rear diff is ring and pinion is not perfectly set up but are really close(checked when changing the fluid). I went by the drive line shop and he is telling me to do the oposite of what I have learned here. he says to remove my 6 deg shim and aim the pinion towards the tcase more(I installed the shims with the 10 bolt due to a wobble when accelerating from a stop. a 2 deg was not enough.)

    I think the drive line is to short and vibrating in the transition between load and off load.

    Ideas? experience? knowledge?
     
  2. mouse

    mouse 1/2 ton status

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    Standard drive shaft or CV? If its standard, then I agree, it sounds like it may be a bit short, and removing the shim will make things worse. If its CV, get rid of the shim.
     
  3. ssped

    ssped 1/2 ton status GMOTM Winner

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    It is a non cv drive shaft to a 208. if it was ujoint angle issue they would be getting hot from binding on a longer drive? I am no finding any heat at them at all. When looking for a tcase issue I had the electronic ears on there and it sounds like there was some noise at the tcase tail shaft. I replaced the tcase. when I pulled her apart I found a bent main shaft in her from the rear diff disintegrating on me.

    The drive line is in perfect Phase as recomended everywhere. why does he want me to raise the pinion ange up?n Hmmm I wonder what he is thinking.
     
  4. Masiony

    Masiony 1/2 ton status

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    perhaps he in compensating for axle wrap?
     
  5. ssped

    ssped 1/2 ton status GMOTM Winner

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    Isn't axle wrap the pivoting of the pinion up when accelerating? the pinion is 2deg up towards the Tcase and the Tcase is 2deg aimed down. To me (in my inexperienced opinion) the drive line angles are perfect. I spent weeks playing with it to get the wobble out of there when you accelerate and just when everything was perfect the rear Diff tore off the Axle tubes. now I am dealing with a whole new mess of issues.
     
  6. Masiony

    Masiony 1/2 ton status

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    how confident are you that your driveline is in balance?
     
  7. ssped

    ssped 1/2 ton status GMOTM Winner

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    newly made drive line by drive lines unlimited. It is good. I am going to shim up 2 deg and see what happens.
     
  8. 1977k5

    1977k5 3/4 ton status Vendor

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    Theoretically having the t-case and pinion angles the same is the right way to go. In the real world, you have probably severely exceeded the maximum angle that your u-joints can handle without vibration, regardless of how well they are set up. IMO, your choices are to try it without the shim (1st choice because it is free) and if that doesn't make it any better (it probably won't) you can either deal with it and expect some higher maintenance or buy a CV driveshaft for the rear ($$$$). Most on this site probably just deal with it.
     
  9. ssped

    ssped 1/2 ton status GMOTM Winner

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    That is kinda what I was lookin for. I am throwing the Book at it right now. it is in the shop and they are re setting up the rear Diff, gearing the front to match. extending the driveline on the rear and rebuilding the front one and of course shimming the rear up 2deg. if that does not work I am going to live with it. I just want to be able to drive her on longer trips and not worry about breaking anything.

    Will find out tomorrow afternoon how she is.
     

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