[samboy1123]

Hey guys,

I'm having a few issues with what I'm 99% sure is my rear diff in my 95 sierra. I'm getting a whirring/howling noise only under load, it's loudest at around 60km/h at approx 3000 rpm but goes away when cruising on the highway. I've recently replaced my rear uni joints and whilst the rear drive shaft was out I drove around in front wheel drive and the car was quiet hence why I'm thinking it's diff related. I have not much of an idea when it comes to diffs, so what I'd like to know is;

What do you guys think is wrong?
Should I go with a rebuild or new center?
What's a good price for a rebuild and what's a good price for a center?

Cheers.

Sam.

[droverdave]

Theres 2 things to go wrong with diff centres and cause noise.

-Differential centre bearings (there is 2 on the pinion, and 2 on the carrier)
-Worn/damaged crown wheel and pinion (the gears them selves)

Worn bearings, in my experience, are a constant sound, doesnt matter about load, just whenever the diff is spinning.

Worn gears can change depending on the load applied. When on load the teeth are touching and rubbing, and if worn can cause noise. but when off load the gears will have no force applied to them, thus the noise goes away.

To fix a bearing issue, its around $130 in bearings, a new pinion seal (~$20) and a crush tube (~$20), and a reasonably complicated setup procedure (i did it last weekend, and its not easy even with the correct tools).

To fix a damaged crown/pinion gear....you get different ones. Weather that is 2nd hand and hope they arent as noisy as yours. or perhaps you can buy them new from somewhere.

From what you describe, the sound changing with load, id say your crown wheel and pinion is damaged. Might be best to grab a second hand centre ($70-100) and check the teeth condition before purchase.

[samboy1123]

Thanks for the help. Struggling to find a center under $300 atm, one will turn up though. When you say teeth condition is it easy to spot a worn diff?

[Gwagensteve]

Problem a can result in problem b too. Pinion bearing failure will trash the gears in time.

[droverdave]

Some good photos in here.

http://www.differentials.com/technical- ... e-analysis

300 bucks?! geez.

[samboy1123]

Thanks guys,

Looks like I'll definitely be up for a new center. Another question, is driving around with the rear drive shaft out going to cause any issues? Other than the obvious extra wear on the front diff.

[samboy1123]

Actually $350,$450 and $300 haha all from wreckers though.

[Gwagensteve]

Tooth wear can be quite hard to spot too.

Driving around in front wheel drive is pretty dangerous. I wouldn't do it.

[droverdave]

You can have a look at teeth contact patch using bearing blue, but im yet to try that.

[Reubs]

Gwagensteve wrote:

Driving around in front wheel drive is pretty dangerous. I wouldn't do it.

Steve,
Just curious as to why that is the case?
Reubs.

[foolishme83]

"Driving around in front wheel drive is pretty dangerous. I wouldn't do it."

I'm curious too. Would the extra strain on the front end cause it to explode or something?