August 2010 Issue - 7.625 Inch Rearend Overhaul

7.625 Inch Rearend Overhaul - 10-Bolt Basics - Tech
Overhaul A Factory 7.625-Inch 10-Bolt Rearend For Our Project Sti Killer

From the August, 2010 issue of GM High-Tech Performance
By Justin Cesler
Photography by Justin Cesler


Question is how much RWHP can this steup take?  
1999 Custom TransAm

Doubleome,

Even with all of our modifications, the 10-bolt is still susceptible to breakage. I would feel comfortable with 450-500 rwhp on this setup, but I would make sure to take it easy with sticky tires and an aggressive launch. On the street, you could get away with more power, assuming you let the tires slip a bit under power.

What is your current setup and what are your goals?  

I have sway bars, sub frame connectors, tower brace, ploy motor and trans mounts.  Trans cooler, K@N Air filter, 3 inch true dual custom exhaust (exiting in front of rear wheels), and 160 degree thermostat.  My end goal would be 500PH to the wheels but due to just being stationed in Colorado the altitude is going to play havoc on my RWHP.  I'm not a big drag race patron but I do enjoy the occasional burnout with a little ricer spanking on the weekends.  The other flaw in my plan is I have an automatic…..  yep I said it out loud. A..U..T..O..M..A..T..I..C  I’m looking into counseling.  Thanks for the response and I truly enjoy reading GM High-Tech Performance magazine.  
1999 Custom TransAm

Don't worry about the automatic, my WS6 Trans Am is an auto and I LOVE that car. 500-rwhp with a 4L60E will help keep your 10-bolt in good shape. I made around that on an early nitrous setup (ran 11.1 @ 125) with a stock 10-bolt, so an upgraded unit like the one we just built in GMHTP would have no problems.

Have fun out there and keep us updated on the progress!  

If you have been around third- and fourth-generation F-bodies for any length of time, you probably already understand that the stock 7.625-inch 10-bolt rearend isn't exactly the strongest unit on the planet. In fact, one could argue that the factory 10-bolt is possibly the least capable rearend GM could have used in these high-performance muscle cars. Besides being physically small, the factory rears seem to have an issue keeping teeth on even the stock ring and pinion, a problem that gets worse with every additional ft-lb of torque you throw at it. Replacing the ring and pinion can even make the problem worse, as a steeper gear (numerically higher) means the teeth have to be thinner, further weakening the rearend and making it even easier to break. To add insult to injury, most factory and aftermarket 10-bolts, even in working condition, can exhibit a nasty gear whine, the result of both subpar installations and distortion.  
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