Torsen with 3.73 Motives. I finally bit the bullet and took my car to the shop to get the rear end set up. Everything was done right with the correct preload, pinion depth and backlash but it still has a little whine. Not during acceleration, not during deceleration but in between when there is just a little pressure on the pedal. I set the gears up myself before and ran them for about 8k and wasnt totally happy so I took it to a pro. They told me the pattern I had worn might make a slight whine, which it does. Will the new (correct) pattern wear in and quiet down or can I use some thicker fluid (75w-140) to quiet it or do I just deal with it?

 

If the pattern has been worn into the gear, its nearly impossible to get them to be quiet, Its just something you have to live with. To me it sounds like a minor problem.

 

Changing fluid won't change the sound.

 

My gearset was run for about 8k before I had it set up professionally and it has a slight whine. If it is truly set up correctly, can the old (wrong) pattern cause a little whine like that?

 

Yes..

 

Well for all who care, I got the car back from the shop and the finished product has .032" pinion shim, 18 inch lbs of pinion preload and backlash was set at .008". It has a slight whine in the 50-65mph range but not terrible. I might change the fluid to synthetic 75-90 with some additive or just put in some additive and leave it alone. I will just have to live with a little noise I guess. I haven't really gotten a straight answer if thicker fluid would help or hinder so I will stick with the regular stuff. You live and you learn I guess.

 

I am at the same point you are. I rebuilt my axle myself for the first time. I get a light hum at the exact same speeds. I am breaking things in with 75W90 oil and have the GM synthetic stuff waiting to go in. My stock gear made the exact same noise at the same speeds but slightly less loud. I know for a fact that as the fluid heated up the noises got much more noticeable and each morning when I set out they are much quieter. The effect was much more noticeable during early break-in. I even would hear the torsen making zipper sounds when turning when the fluid warmed up. Do not discount the effects of the fluid regardless of what anyone says.

Here is my current gear pattern. My backlash is a little tight at about .0045" averaged in three places.



Drive Side on the left, Coast Side on the right.

For comparison, here is the factory pattern which had a huge .013" back lash

 

What do you mean when you say "Do not discount the effects of the fluid regardless of what anyone says." I have found that gears are very tricky and if gears are run at a wrong pattern, the sound will never go away regardless of whether the new pattern is perfect. And I think .0045 on the backlash is a little tight and might get a little hot, that is very little room for the fluid to get in there. Just my humble opinion from the info that I have gathered.

 

Not disagreeing with anything you are saying there. People in some threads have stated that the fluid makes no difference at all to the sound, when in fact it does, I was hearing it each day. You are correct in saying that good gear set up is more important than the fluid. I do intend to top open my back lash up a bit. Does the pattern I have now look decent to you?

 

Ahh.. what the hell. Just run an ISO 250wt.

 

fluid does matter i run the 140 and additive to keep things quiet in my z71 and about to do my z28 and will run the same stuff which will be synthetic!!