If so, please let me know how fast you were running (60' especially) and whether it was auto or manual trans.

I'm doing a bit of research on the 9-bolt and would appreciate the information.

 

The few that I've seen were due to excessive clearance between the spider gears and the side gears which was due to wear. This causes significant impact loading on the gears and the spider as well. Most ring & pinion failures are caused by too much backlash (improper setup and/or wear) or worn pinion and/or carrier bearings.

I have been running mine for 3+ years now behind my big block (500hp/520lbft) with 1.72-1.75 60 fts and not a single problem (originally with a 3.27 gear and currently with a 3.73 gear. Going to try a 4.10 gear this spring ).

Miles

 

The gear isn't broken, but the posi is very weak. This is on a fairly stock L98 is good tune.

It became apparent on an open track day at a road racing course (Nelsons Ledges in Ohio). At the start of the day, the posi was working fine. At the end of the day, it wasn't working. There are two possible places where I put the posi unit "over the edge".

Situation 1: I was entering/into a decreasing radius, off camber turn in 3rd gear. Just past half-way through the turn, a downshift is required. I managed to grab 1st instead of second. The rear end kicked out and the revs swept past 6,500 (no rev limiter!) before I was able bump it back into neutral. I hate automatics!

Situation 2: The fastest way through one of a series of turns (hard right to hard left to hard right switchback) seem to be to downshift to kick the rear out going into the entrance of the left hander. This got the car pointed straight very quickly into the short chute into the last right hander. I did this all afternoon and this put alot of stress on the drivetrain.

As I said, this is a stock car, but I spent a whole day hammering the drivetrain, only wearing out the posi (hey, it's a 90k+ mile car). I have no concerns about the rear gear - it seems pretty solid.