One of the best performance modifications that can be made to a street machine is a change in rear gears. Going from a stock, economy-minded 2.73:1 ratio to a 4.11:1 performance gear can transform a lethargic loser into a leapin’ leaver. You’ll swear you found another 50 horsepower somewhere. The bad part is that while simple engine bolt-ons can be done by almost anyone with a hammer and a screwdriver, changing a ring-and-pinion gearset is much more involved and requires some dedicated tools that you probably don’t have. This is especially true of the GM 10- and 12-bolt rearends, but we’ve recently run across a few trick tools that make it easier and less expensive to set up the GM rearends at home.
The accompanying photos and captions will show how to install the ring-and-pinion gears and set them up with the correct clearances and specs. We won’t get into rebuilding the differential here. For the juicy details on how to do that and how to get more performance out of the diff, check out Improve Your 10- And 12-Bolt Positraction .
