I am at my Whit's End with chasing this noise! It's a 94 Z28 with 4.10 in the factory rear 10 bolt. Whenever there is torque to the drive train, i have a very loud, high-pitched noise. When you let off, the noise goes away completely. It sounds like its coming from the rear end, but I'm starting to wonder. I've been in the diff three times now and nothing has changed. The first two times I've messed with my backlash and brought it down to .008 from .022. This last time I bought an install kit and replaced the bearings and set-up the diff the right way, but no change at all in noise. The only things I can think of are the ring and pinion itself, axle bearings, or something in the clutch transfering through the driveline. I rebuilt the T56 already so I know that's not it (I did not replace the clutch as it was still good). The car has been doing this since I bought it! Any ideas? I'm sick of buying all this gear oil just to go to waste!

 

what brand of gears?

i went through a few sets of richmonds and they all whined.. nature of the beast.

 

I'm not sure what brand they are. I'm aware the Richmonds whine, that's why I looked. I could not find a manufacturer on them, just numbers.

 

Its the ring and pinion. My damn factory 3.42 rear is starting to do the same damn thing. I remember going through several sets of 3.73's with the same bad luck as you. These 7.5's are a pain in the ***.

 

its your gears. I had motive 4.10s in mine and they began to whine within 2 weeks of install. Gene at thunder racing told me this was normal, especially for 4.10s or higher with an m6.

 

I can understand a whine, but this is almost unbearable. It's almost embarrassing to drive this thing! It's very loud and high pitched! Not that I don't believe you guys though. I just wanna be sure this time.

 

If its that loud, its your gear setup. I had a guy attempt to install some gears one time, they were so far off they howled very loudly! So loud it was heard by the cars next to me.

Go with GM gears, and get a professional to install them.

 

If the gears were setup improperly then driven for ANY period of time they will "seat" themselves and no matter how you adjust or re-setup they will always whine until they fail.

Only way to get rid of the whine or reduce it is to get a new set of gears and find a place that KNOWS how to setup 7.5" 10-bolts; they can be a pain in the *** to get right.

 

Any performance ring and pinion usually whines. It's because they are harder than stock gears. You can get GM gears and they will be quiet if set up right, but they might break, or you can get performance gears that will whine but not break. I got mine down to only whining between 45-50 mph and the rear end shop in town told me I did better than they probably would have.

 

My stock 3.42 geared rearend does the same thing. It's been doing it for the last 10,000 miles. Only whines under throttle and usually can hear it on the highway. Can't hear it with the windows down or the radio on, so I ignore it.

 

My 10bolt with 4.10s whined at highway speeds. I blew 2 of them and got an S60. No more whine

 

I experience whine around 55-65 mph. If the differential is not under load at these speeds, the whine ceases and also decreases significantly after 65 mph. You can't hear whining as highway speed increases above 70 mph. From reading the blogs posted , this may be normal for a high performance gear set.
The gear set has about 500 miles on an entirely new installation by a trusted mechanic with a deluxe installation kit from Thunder Racing

 

I personally think if its that loud then you have the pinion setup wrong, backlash is the easy part, its placing the pinion in the correct spot, and tightening the nut to achieve the proper preload on the bearings that will make or break the install, and since most people dont have the tools, or the experience to know when to stop tightening, this is the result. I would wager to say you have the pinion too loose, hence causing it to "pitch" under load and off load. I have done a good handful of different rearends now, and I can now actually feel when the pre-load is right by hand. The proper way of course is to use an inch/lb. torque wrench (the flexible beam style) and tighten til you get the right pre-load (which is usually like 15 in/lbs. for used and 25 in/lbs. for new pinion bearings, without the diff. installed), but thats only half of it, and w/o the proper tools or knowhow to read the rign and pinion once moc-up is completed, you have no idea where the pinion is riding the ring. The ring needs to be centered on the pinion, and alot of the time you can re-use the shim under the bearing, but sometimes you need more or less depending on the manufacturer of the gearset. Thats why its easier to stick with gm gears for a gm rear, because they're usually marked +/- with some numerals. These are the variances from the "baseline" pinion they would call "prefect". Then you add/subtract shims depending what you had originally. Its not as easy as everyone thinks. Some ppl get lucky, alot of them dont.

 

Thanks for the information. With fewer than 500 miles on the install I'll have the mechanic look at the gear set.

 

It's nice to know I'm not the only who went through several sets trying to take "noise" out of the rear end..!