Rear Differential

I have a funny feeling my rear differential is on it's way out. Might be a chipped tooth. Just want to see what you guys might think, to see if that is the case. It just recently started doing it. When I'm cruising at low rpm's I hear this "whoo whoo whoo" with very faint knocking. The knocking isn't on sync, so my guess would be something may be bouncing around in the diff. It drives like a champ, you wouldnt even be able to tell if there was a problem if the radio wasnt off and the rpm's were low (to quiet the exhaust). So I can't "feel" any difference in drivability. But from what I've been told that "whoo'ing" sound is a detection that there's a problem with it.

If this is the case, then by chance does anyone have any gears or a rear posi/limited slip differential. They don't have to be new, but were at least not beaten on with hard driving (ie: took it to the track often, have a lead foot, you know who you are). I would like a set of 3:73's (but will consider others) and any name brand posi unit. Not like it has to be top of the line that handles up to 500 rwhp, it's just going in a V6.

I don't exactly have alot of cash to throw into this, so thought I'd see if any of you might be able to help me out. Shoot.. I gotta spend about $350 on books for college (and that's just for 4 books, which btw you only get about $20 for each one when you return it). And I'm also pretty sure either my rear main seal and/or my intake manifold/plenum gasket is leaking... So yeah, more money to throw at that.

Try to find a lower mileage one off a V8 4th gen.
Gonna be the cheapest option.

Not sure how it fits to the V6 car though.

Also forgot to mention that when I start it up only after having it sit for longer than 10 minutes, the whole rear end just vibrates. It even makes the hatch vibrate. It goes away after about a minute or two of driving though.

rear end vibrates or engine/tranny vibrates? since the differential is just basically gears (i think) its weird that it would change operation after it warms up..

have u checked the rear gear oil? a friend of mine has a 1991 firebird who's rear end made a whine noise and he checked the oil and it was real low.

Figured out the problem... I got a chance today after work to look at it. Turned out to be my U-joint on the forward end of the driveshaft. I can easily wiggle the driveshaft back and forth. It could possibly also be unbalanced as well. So, thus, I demand a refund John!!! j/p, shit happens

Its balanced but when I first started out selling these I didn't have the press and therefor didn't offer the upgraded U-joints. U-joints are a very commen thing to go (thats why I bought the press and started recommending that the joints be changed). Sorry it happen but the driveshaft itself is balanced. That I assure you.