The first one broke with 3.73's and an aluminum cover and synthetic oil in it.

The second one had 4.10's and I broke 3 teeth off the ring gear and lost my carrier in the process.

Bought a zexel torson carrier and new GM Motive 4.11's and had a solid pinion spacer installed.

I warped the housing and lost a carrier bearing which took out the rear end again.

4th rear end lasted the longest, bought whined like crazy, my mechanic tried to do some voodoo and set the gears up looser to cushion the teeth, worked for a while broke still gave out while I was flooring it in 3rd gear.

All of these broke with nitto drags, only the first two happened at the track.
The later of the two where both broke from a third gear roll while tuning my nitrous system.

 

How much RWHP and what clutch???
Thanks
ps. So it seems that befing up 10bolt is usless???

 

Unless you plan on keeping it almost completly stock and never putting sticky tires on it I say putting any money into a 10-bolt behind a 6-speed is a waste. I broke mine twice on street tires. The first time the carrier (stock) broke and the second time the gears (GM 4:10's) broke. I would have had the 9-inch half paid for with the $$ I put into the 10-bolt. This was with 350+ RWHP, stock clutch, and Pep boys tires (275/40ZR17's).

 

i broke my stock one going over train tracks at 30 mph coasting, got back on it (not hard or even remotely hard) and heard the clunking begin. car was mainly stock at that point. The 10 bolt in my car now is pretty beefed up. Auburn Pro Posi, Richmond 3.73 gears and all the supporting parts. Has held up to my heads/cam full bolt on 6 speed 295/35/18Drag Radialed Street Drivin Beat downs for a year now

 

not only can you break it, but you will when it gets traction. Maybe not the first time, maybe not the second, but it will break eventually. The 4.10s dont help matters any. I've seen people break stock rears with much less tire.