whine in differentials

While im driving im hearing a significant whining noise coming from the rear. The sound only occurs while im coasting with the transmission engaged around the 40-50 mph range. Otherwise there is no sound. How much should I worry about this thing dieing out on me? Im not hard on it at all. I cant hook worth a crap so it isnt getting a whole lot of stress. And as far as i know the posi function is working fine. Just when i let off the gas at around 40-50mph. If i push the gas back down the whine goes away.

Hello 92zcamaroperson, My 97 does the same thing. I have the 3.8 auto with 120 K. Generally, I think this noise is nothing to worry about. It is the nature of the beast on a rear wheel drive car. I had a 318 '71 Plymouth that did this its whole life. That said, makes me want to check my lube and make sure it is full. Here's what my book says....

If the level is below the bottom of the filler plug hole, you'll need to add some lubricant. Add enough to raise the level to the bottom of the filler plug hole.
Standard Differential - use axle lubricant GM part #12345977 or SAE 80W-90 GL-5 gear lube.
Limited Slip Differential - To add lube when the level is low, use axle lube GM part #12345977. To completely refill after draining, add 4 ounces of Limited Slip Differential Lubricant Additive GM part # 1052358 then fill to the bottom of the filler plug hole with axle lube.

Or, just ask the guys at the oil change place to check the differential lube next time you get a change. As long as it isn't clunking and clanging I wouldn't worry. JJ

I wouldn't trust an oil change place with my differential oil. Then again, I plain out wouldn't trust an oil change place.

Change the oil, but the additive in, and see fi it goes away. That's what usually happens.

werd on the no lube place. But yeah i guess that would be the best thing to do. Any suggestions on what brand of diff fluid would you suggest? And then posi addidtive?

mine does the same thing 92z at the exact same speeds and when i take off under light acceleration...i replaced the fluid with synthetic mobil and it still makes that sound....so iono

You can tighten up the backlash a bit and that will usually take care of the noise.
All the whine noise is, is the clearance between the ring and pinion.
The noise will occur even if the backlash is in specs, but going on the tight end of the spec will eliminate the noise.

You can tighten up the backlash a bit and that will usually take care of the noise.
All the whine noise is, is the clearance between the ring and pinion.
The noise will occur even if the backlash is in specs, but going on the tight end of the spec will eliminate the noise.

how exactly do you do that? thanks!

what he said. ?

"I wouldn't trust an oil change place with my differential oil. Then again, I plain out wouldn't trust an oil change place."

Good call there Savage! I do trust my oil change guy though... good long time friend who has saved my rear on many occasions. Sharp eyes he has for stuff I wouldn't have ever noticed. JJ

i have some 3.73's on order...will be better than the 3.08's i have now and ill just have it all fixed then by a shop

hey merlin. How do you go about the backlash tightening?

i was told that you have to take the rear end apart to tighten the backlash...with that im just going to have a shop swap gears and be done

i want to put a girdle on it. Id like to find a decent set of street slicks so that I might hook once in a while. Im just afraid of tearing something up back there because the 10 bolt isnt supposed to be the most ideal for that.

BFG drag radials are my reccomendation

do you think itll snap my rear? Or break my posi?

no guts, no glory :D

Which do you think would go first? The posi or the gears?

well theyre drag radials not slicks. You never know ... may want to pick up a TA girdle just in case tho, I know I will

ALright, you bought that car pretty beefed up already right?

I find it hard to believe somebody would have all the suspension goodies in it and have a dead dog stock rear.

Are you just spinning at the line or hopping the ass end all over on a take off?

anywhere in first gear I can break it loose real easy. Take off I cant hook unless I ease into it. And say I goin 10~15 mph and i punch it the back get loose then. Im not trying to launch or anything and Im not laying my foot all the way down in the gas from a stop. Maybe I just need different tires....they are goodyear eagle f1's. Supposed to be good tires. I have some bfg KDA's (somethin like that) that Im going to be putting on soon. Maybe those will help. I was riding around with some guys going around to the late night spot in parking lots where people meet up and get stupid with burnouts and such till the cops come. Anyways the guy I was with (whose car has a carb 383 lt1 with all forged internals and the cam with about 580 lift, makes about 475~500hp, sounds SICK!!) he did a wicked burn out and after he did I put my hand on his tire and freakin that thing was sticky as crap! He has 315's bfg KDA's. This is all on a third gen. Those tires must stick out about 3 or 4 inches from the fenders.

Gear whine is very commen in gears with a very high nickel content (such as richmond & strange gears). How you tighten up backlash is by using a shim kit and using smaller 1/100's of a inch shims and taking space away from the passenger side shim pack and adding to the driver side. This moves the ring gear closer to the pinion gear and takes up any slack but in doing this you want to make sure you leave at least .004's play (measured with a dial indictator). I would recommend swapping in some sythetic gear oil with a posi additive before attempting this though.

Also, the weak point of all 3rd and 4th gens rear is the ring gear. 7.625 is too small for any performance car.