Decided to have the leaking pinion seal replaced on my black 91 RS convertible with 110,000 miles. The rear was quiet no whine & no roar before going to the shop. The differential had been serviced every 30,000 miles by the prior owner per the maintenance records. The car has never been abused or beat on.

Drove 45 miles as normal with new pinion seal then crossed a rough railroad track and the rear end started making noise. Checked no leaks. Drove about 20 more miles including return to the shop and rear end roars above 25 mph and noisy over 10 mph.

Shop determined the front & rear pinion bearings are toast and must be replaced. The side carrier bearings are also toast and must be replaced.

Is $750 reasonable to replace the bearings?

Ring & pinion gears have norm wear pattern and are ok.
Axle and axle bearing are ok.

Any insight on what would have caused the issue?

My other 91 camaro has 385,000 miles on the same parts and no issues, no replacements with Mobile 1 gear oil & GM limited slip additive. Likewise 99 T/A has 10 bolt with 4.10s has been beat on for 135k and no issues.

I was very surprised the rear in the car that's never been driven hard with 110,000 miles failed.

 

It's around 5 hrs of labor, if you're re-using the gears. About 3½ - 4 for new gears. Figure $80/hr for labor; $750 sounds high. Unless they're supplying the parts, in which case, ... it's still a bit high-ish. http://www.summitracing.com/parts/yga-14077

Most likely the crush sleeve lost tension and allowed the nut to back off. Pretty commonplace. Consider having em put it back together w a solid spacer instead. http://www.summitracing.com/parts/rat-4111

Luck o the draw...

 

If they just replaced the pinion seal then I'd say that they screwed up when they tightened the pinion nut and messed up the preload on the pinion bearings.

 

When by shop and checked parts myself.

One carrier bearing had chunks missing on a couple of rollers. The other was scored. Pinion bearings looked fair. Ring & pinion looked good as did axles. All parts had fresh 75w-90 oil on them.

Talked with a friend back home in Carolina who is an outstanding mechanic and engine builder. His take was for the carrier bearings to be wasted like that differential had to have run low on oil at some point. Likewise $550 to $650 would be more inline with expected cost for most shops for this repair with them providing all parts etc. Also suspected pinion likely over tighten with an impact wrench instead of being done by hand. If over tightened you can't just back off due to crush collar etc.

I talked with shop about the solid collar in the link above. Short version cost would go up because all of the shims etc would have to be changed ie whole rear set up would have to be adjusted. Mechanic had zero enthusiasm for the idea maybe a little uncomfortable either with how long that would take or the hassle involved.

Decided to let them do it their way for warranty reasons if another problem occurs.

Thank you for the input and comments. It was very helpful.

Best regards.

 

Btw everyone says this a pretty common issue with these cars...I'm amazed that with 700,000+ miles driving 3rd & 4th gens I've never encountered it.

 

Bearings go bad. It happens. Low oil probably was not the reason for the bearing to go bad. I've replaced more than 100 that were like yours that had never been run low on oil.

A solid spacer is harder to set up because you have to do several trial assemblies to get the bearing preolad set right. A crush spacer takes one shot and it's done. I completely understand why they didn't want to install the solid spacer.

 

Obviously doesn't understand how it works, and didn't bother to compare that, to using however many crush sleeves it takes to get the pinion depth right if it needs messed with (or worse... re-uses em)

Because of course, if it takes him longer for some reason (which it won't, but w/e), he just charges a bit extra, right??? Not a big deal there, for the shop.

Me too. One word: LAZY.

All in all it seems like this is not the shop you should be dealing with anymore.

 

Yeah, I'm suspicious. No trouble until AFTER that shop had it apart working on it? I wouldn't be crazy taking it back there to give them more money for something they broke.

 

The shop doing the repair has the best overall reputation in the community I'm in for being honest, standing behind their work & getting it fixed right the first time.

The total cost was right at $750, with discount coupon it ended up being $675. Parts were listed at $280, labor at $410, synthetic oil $30 plus tax.

Car drives like new and there isn't any noise from the rear.

I had planned to have the transmission fluid changed next week...but may wait for a while...I've had enough repair bills on this car in the last six weeks...right at $2000.