Differential Problem? Buy a Quaife?

[gowhoosh]

Hi all, car is a '94 Z32 Twin Turbo, 5 speed manual, with the stock R230 differential. There is an obnoxious squeal coming from the rear end of the car, and sounds like a wheel bearing gone bad. It is present above ~40mph, and only under acceleration. If I am going 80mph, it will be screaming at me, but if I let off the gas, even a little, it will completely go away. It's all or nothing, it does not vary in volume, except slightly given a large difference in speed (such as 40mph compared to 80). The previous owner's mechanic had told him the problem was with the right rear wheel bearing, which I blindly accepted as fact and replaced. It didn't help at all. I was a little suspicious that it could be my tires, as they are Goodyear Eagle F1's near balding, and reviews claim they make a similar noise. I jacked up the car, and had my buddy drive between 50 and 65mph in 3rd gear repeatedly, up and down, as I was under the rear end, attempting to isolate the noise. The only sound was about a tenth as loud as normal, and seemed to be coming from the differential, specifically the input. I couldn't really narrow it down too much though. So, I'm pretty much looking for the next step to find the problem. Has anybody experienced this? Should I drain and change the gear oil in the diff (could be low or empty), rebuild it, or, what I really want to do but would devastate my bank account, buy a Quaife HLSD? Any help/advice would be greatly appreciated, as I am fairly stressed and confused about what it could be. Oh, also, about the stock R230 LSD in the Z32TT, is it a clutch-type, viscous coupling, or some other kind? Thanks again.

[es.biggs]

Z32 has the viscous coupling LSD...here is what I'd do:

Check driveshaft center support bearing (common problem)
Check diff fluid level (if it's low top it off, if it's full see below)
Drian and fill diff fluid

See where that gets you

[gowhoosh]

Thanks man, will do. It looked like the driveshaft was split into two sections, and I assume the center support bearing is located at their joint? And how would I go about "checking" it? Should I just replace it or is there any sort of test I can do?

[robomatic12]

Yeah the center bearing is located at the joint between the two half shafts. Rock it up and down and side to side. There shouldn't be much play in it. You can also run the car up in the air, safely of course and see if there is any noise coming from that bearing.

[gowhoosh]

Okay thanks bro.

[es.biggs]

yeah my csb is bad now, I can move my driveshaft maybe 2 inches up and down at that bearing