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Need Help Quick With Gear Noise!!!

This is a discussion on Need Help Quick With Gear Noise!!! within the Drivetrain forums, part of the LSx Technical Help Section category; Me and my cousin decided to tackle replacing the rear end gear ourselves about a week ago. I have a ...

  1. #1
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    Need Help Quick With Gear Noise!!!

    Me and my cousin decided to tackle replacing the rear end gear ourselves about a week ago. I have a '93 Formula that used to have 3.23s and now has Motive 3.73s. Everything went pretty well and we measured .008" backlash (Motive recommended is .008" to .0012"). we reused the old shims. We have no way of measuring Pinion depth, and we thought that since the head of the pinion (teeth part) was .0015" longer then the stock pinion head, we would use a smaller shim. The result was a constant (however not too loud) gear whine.

    So today, we took the advise of the install guide mentioned under the FAQ sticky and my local shop and put the original pinion shim back on. Backlash remains .008". The new result is slightly quieter whine while driving, but an extremely louder whine while deaccelerating.

    What happend and what did we do wrong? I know the original pinion shim (currently installed) is .0030" thick. Is this normal? How do we fix this?

    I appreciate anything you can offer as soon as you can as I am afraid to drive my car in its present condition.

    Steve

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    Nitrous Tuner LS2Tuner's Avatar
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    Did you replace the crush sleeve............?



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    Yes, both times.

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    I should add that since I don't have a inch-pound wrench, nor do I have any specs telling me what the foot-pounds should be on the pinion nut, it was suggested to me by someone else that there might be too much play on the pinion as its not tight enough.

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    Quote Originally Posted by Shudson105 View Post
    I should add that since I don't have a inch-pound wrench, nor do I have any specs telling me what the foot-pounds should be on the pinion nut, it was suggested to me by someone else that there might be too much play on the pinion as its not tight enough.
    Thats possiable. Does it spin pretty easily?

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    Yea, it does. I am going to try to tighten it up some more this weekend - I hope. I don't have to take the whole rear-end apart to do that do I? Think it would be safe to just disconnect the driveshaft and tighten it?

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    Quote Originally Posted by Shudson105 View Post
    Yea, it does. I am going to try to tighten it up some more this weekend - I hope. I don't have to take the whole rear-end apart to do that do I? Think it would be safe to just disconnect the driveshaft and tighten it?
    Yes that is fine. You need a quality impact and atleast 100 psi. Did you tighten it by hand?
    If so that is atleast part of your problem.
    It should turn like it has friction on it.

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    Thanks for your help LS2Tuner - Finally got the pinion nut tightened enough this afternoon with a new impact gun, borrowed an inch pound wrench to verify pre-load and eveything is good there. However, I am still getting some gear whine. Its quieter then its ever been before, but still noisy enough that I can hear it. On a scale of 1-10 it went from an 8 down to a 3. As I mentioned before, its a Motive gear, I reused the old pinion shim and I have backlash set at .008". All other hardware is brand new stuff from Ratech. The whine doesn't sound unhealthy, but just the fact that it is there annoys me and makes me think something is still wrong.

    Any thoughts?

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    Did you mark the ring gear and roll the gear to look at the pattern?
    It sounds like the pinion was up on the heel and when you tightened it it brought it down towards the toe. So how much did you end up with inch pounds that is?

    What weight oil did you put in it?

    The noise is under a load or coast?

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    The gear pattern runs slightly toward the inside of the ring now. My chiltons manual said 24-30 inch pounds pre-load when using a new crush sleeve and it's right at 30. Im using 75w90 Mobil 1 gear oil w/ one bottle of GM lsd additive. The noise is under load and coast.

    What is the heel and toe of a pinion?

    When we first set up the rear end we didn't quite know what the pinion depth was since we didn't have a depth guage. We used a slide rule in .001" increments to measure the face of the old pinion to a set point and mocked up the pinion with different shims till we got the same reading on the new pinion. The result was a shim half the size of the original. As mentioned in my first post - we realized our mistake and took the rear end apart a week later and put the original stock shim back on as suggested by every person/shop/manual I consulted. We blew up our impact gun trying to install the pinion nut with another new crush sleeve, and therefore ended up at the begining of this post.

    Steve

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    So by changing the heel and tow you mean the angle at which the pinion meshes with the ring gear?

    Would the side the shims are on in regards to the carrier make a difference? For example: I have .005" on the left and .003" on the right, versus .003" on the left and .005" on the right?

    I had a mechanic co-worker listen to my car and he feels it's pretty quiet as is and I should just leave it alone, but it still bothers me.

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