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Pinion/driveline angle problems... vibrations

This is a discussion on Pinion/driveline angle problems... vibrations within the Drivetrain forums, part of the LSx Technical Help Section category; About 3 years ago I had a shop replace the rear end gears (4.10) with the factory gears (3.42) after ...

  1. #1
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    Unhappy Pinion/driveline angle problems... vibrations

    About 3 years ago I had a shop replace the rear end gears (4.10) with the factory gears (3.42) after the gears broke in the differential. For a while it was okay but I noticed later that my toque arm mount was bad and I replaced that. When I came to a stop, the back end of the car would slide forward. The new poly mount stopped that. Then I noticed that the trans mount and motor mounts were worn as they were factory. Again, I replaced with poly mounts. I was thinking that the vibrations and clunkyness would stop but they proceeded to get worse. As the car had been worn into the ground, I had to replace the shocks and springs and got the eibach bilstien combo. But still things where vibrating and the car rides horrible. I noticed that there was a noise where the panhard bar is and of course the bushing were bad... so I replaced those as well. And now the vibrations are still there. So I checked the U-joints to see if they were bad and they were snug. They don't move up or down or side to side. Seem solid. However, when I turn the driveshaft or the wheels, there is a lag from when I turn it to when the gears actually catch. So my questions are:

    Did the add ons (motor, transmission and torque arm mounts) change the angle/height of the engine and tranny, messing up the pinion angle of the newly set differential?

    Can I adjust the pinion angle to fix the problem? Or is it not adjustable until I buy an adjustable torque arm mount?

    Or Is my differential going out again and I will have to buy a new ring and pinion?

    The other thought is maybe it is the pinion seal and pinion bearing? I've not noticed it leaking though...

    I've also thought maybe my clutch is going out but I'll deal with one problem at a time... so many though... geez...

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    Moderator 35th-ANV-SS's Avatar
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    If you have the stock torque arm, it is not adjustable. Lowering springs, coupled with the other changes you've made have definitely changed your pinion angle. I would measure it to see where it is at. It should measure around -1.5 to -2 degrees.

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    I don't have any way to measure it yet, I don't even have a lift... just ramps. So what would be the next step, getting an adjustable torque arm or am I doomed with replacing the rear end? Would getting that torque arm and adjusting it correctly solve my problem or do I have too much backlash/lag/slop that my gears are going to break again?

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    Why can't you measure it? All you need is a magnetic angle finder. You can probably measure it with the car on the ground and not on a lift.

    A wrong pinion angle is a great way to destroy a rear end, definitely.

    I wouldn't replace anything before you determine what the real issue is.
    It's on jackstands.

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    Moderator 35th-ANV-SS's Avatar
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    Is the rear end making noise? Have you pinpointed where the noise is coming from?

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    Hopefully I will be able to find a Dial Gauge Angle finder at Harbor freight today. The rear end isn't making any whining or grinding noises. The only thing is the clunky sound and the vibrating... when I'm on the interstate and I let off the gas, it vibrates like crazy. So I'm guessing my best bet is to get the adjustable torque arm? Is there no way to shim it some way to get the correct angle? What would be the best adjustable torque arm to get? I'm not racing and it's pretty much a daily driver, but I want something with good performance.

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