We all know that the 7.625/7.5 10 bolt is a weak component in our cars. What makes them weak?? or More important, what can I expect to brake if I have a higher horse power engine?

The reason I am posting this question is that I have spun the rear pinion bearing on my car. The gears are richmond gears. The gears are three and a half years old. I used all new bearings when they were installed. Backlash and gear pattern were set almost perfect. The gears have maybe 20,000 Miles on them. I mean, comon. There is no way this should happen.

I want to know if this is a common problem. I am leaning towards saving my money for a 12 bolt. I don't want to buy new gears, go through all the trouble of setting up the rear(I can do this my self) and have another pinion bearing spin.

Just a little more background. My engine has about 300 HP and 390 FPT @ the flywheel. The trans was 10,000 AUTO and now 10,000 Miles standard.

What are the common failure of 7.625/7.5 10 bolt Rears?

 

Never heard of a "spun" rear end bearing. They're roller bearings, not bushings cut in half like engine bearings, which are what fails by "spinning"; rollers don't fail that way. They spall, or brinnel, or just turn blue from heat; but they very rarely "spin", unless they get so hot that the rollers weld to the races.

Common failures include the housing flexing enough that the pinion "walks" up the ring, and the misalignment kills the gears (strips teeth off sometimes); twisting off axles; breaking the small gears; breaking the carrier in half around the window.

In addition, bearings can wear out or go bad, usually from improper assembly or contamination or lack of lube.

Rather than assume that some scary-named failure that doesn't apply to the parts in question has occurred, maybe if you told us what it was doing, we could help you figure out what's wrong, or you could take it apart and look at it.

 

like RB said you have a problem when the pinion bearing doesn't spin not when it does. as for what makes them weak is mostly related to size of the parts. like my wife says bigger really is better. not quite sure what she means by that but she says it a lot.

 

Guys, I appriciate your help. But I have already disassembled the rear and yes the rear PINION BEARING SPUN ON THE PINION. I understand you may think that I am assuming, but I'm not.

 

If the pinion bearing spun on the pinion, but the rollers aren't welded, then there's only one possible explanation:

INCORRECT ASSEMBLY

That bearing is a .002" or so interference fit on the pinion shaft. No way in Hades a roller bearing, operating properly, is going to be able to generate enough friction to put enough torque on that race to overcome that much of a drive fit, without any malfunction. In other words, it's not the 10-bolt's fault; it was mechanical faliure, where the mechanic failed to do something right.

So, what form of incorrect assembly, you may ask? Well, it sounds to me like whoever set the thing up, forgot to replace his brake-cyl-honed test bearing with a fresh one after he/she set up the gears. Since that's how we all do the pinion shim thing, is by keeping a head bearing in our toolbox that's been honed out so that we can put a shim on a gear, slide our tool bearing on, test fit it into the housing, measure the depth or check contact pattern or whatever, slide it back off without destroying it and pressing it, change the shim, slide it back on, etc.; until we get it like we want it. Then we slide off the tool bearing and press a new one on. That last step got skipped.

 

Thanks for the feed back. I truly wish that it was that simple. I installed the ring and pinion. I used the brake-cyl-honed test bearings. I know that these bearings were not installed on the rear because I reused them when I installed the gears in my '92.

I guess I am starting to understand that this is a very rare problem. Maybe the Richmond Pinion Gear had a smaller bearing surface??

 

How much force did it take to press it on? What condition was the bearing itself in when you tore it down? The races still smooth and the rollers round, or is it trashed somehow?

 

I don't remember how much force it took to press it on. It was three years ago. The bearing races seemed to be ok. No unusual wear. No chunks or flakes comming off the rollers. The pinion shim was a #20. I measured it after spinning and it was #15. I took the pinion bearing off with very little force. The bearing surface on the pinion worn.

I think I am, for the time being, going to reinstall the old 3.42. I don't have the money to do any thing else.

Not that I'm doing this but if I were to reuse the old 3.73 I would weld the bearing on. How does anyone feel about welding the rear pinion bearing to the pinion??

 

Yea, don't do that.

The dissimmilar metals will not like each other and your weld will crack, and possibly one of the other pieces (race or pinion) may crack too. Then on top of that your tolerances will be different after welding it, and you will have no way to fix it.