I have a 1993 Trans Am 350ci with a whistle / whining sound from the rear end. I thought it was a bad rear end, but I was told it might be a bearing. Which is it? It only makes the sound when driving, not as bad when letting off of the gas, or when coasting. Any suggestions? Thanks , Thomas.

Probably a bearing but may take a tech to find it. There are several bearings in the rear end diff,

T
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Tom Greenleaf - MetroWest, Boston

There are 2 types of noises to come from a differential and sometimes hearing it is the only way to notice the different

A howling or whining noise is usually caused by gear wear or mismatch problems

When you have a bearing problem, it shows as a growling noise. The timing of the noise is pointing to a problem in the pinion area, either the pinion bearing or the ring and pinion match.




78 Corvette Pace Car For Sale-18k mi orig-Florida

how can I check the spacing of the ring and pinion gears? If it is out, can I just correct the problem, or do I need new gears? Thanks for all the replies - Thomas

No, definitely not. the is something that is done with the differential all apart. It requires some real specialized equipment and knowledge and changing the pinion depth means pressing bearing off and on and shimming them. You can't adjust used gears anyway. If they are howling, they have to be replaced and set up in the process.




78 Corvette Pace Car For Sale-18k mi orig-Florida

This description of a rear end noise is new to me but I'll try a suggestion:



It's this style - right? Is the differential one piece or does it go to drive shafts for rear wheels?

It may help to hoist drive wheels and safely have up such that you can allow it to run in gear - get under and listen for area if that helps at all I don't know.

Careful of moving parts but you can use a listening rod like a stethoscope that can be telling. Please use all care and judgement - none of us want anyone hurt over something!

Could this be a brake issue?? Stranger things have happened. If gears are really suspect then removing cover and taking a look would help the diagnosis. They shouldn't show any "pocking or galling on surfaces" and that would call for replacement. Whistling/whining is not all the common to me from rear end troubles. Just the luck the draw.

I have no doubt that Hammer is better at this issue than I am but in the meantime the more info the better to exact the fix,

T
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Tom Greenleaf - MetroWest, Boston

Thanks for the info. I guess this a good time to look at buying that rear end I have been wanting from DTS. Although gravity may not take effect on me any longer with my pockets being emptied of all the money.

I wouldn't give up on it yet. Given the symptoms you describe, it's very possible that you have a bad outer pinion bearing. Although this would still require dissassembling the differential, it can be changed rather easily and the only setup required would be to re-use all the same shims it came with.




78 Corvette Pace Car For Sale-18k mi orig-Florida

Thanks. It couldn't hurt. I'll give it a try. Do I need a press for the bearing, or just some PVC as I use for other bearings?

You don't need to press anything for the outer bearing and that is the most likely one. The lower bearing would have to be pressed off but that one is likely OK.




78 Corvette Pace Car For Sale-18k mi orig-Florida

How do I replace just the rear seal and front bearing? I have heard about a crush sleeve in there that is critical to the rear end.

The crush collar is a collapsible spacer between the inner and outer bearings that will compress using about 250lbs of torque. It should be compressed just enough to remove all lateral movement in the pinion with just the slightest of bearing preload. This keeps the proper amount of tension on the 2 bearings. As far as the steps to do the whole job, it's quite involved and you should invest in a service manual if you are going to attempt it yourself.




78 Corvette Pace Car For Sale-18k mi orig-Florida