The most common question I get from people looking to swap a 7.5-inch rear end into their car is, “How much horsepower can my 7.5 handle?”

The answer? A lot. But how much exactly depends on what gear ratio you’re using, how much force that gear ratio puts on your diff, and how many teeth the ring gear has.

The more teeth on the ring gear, the more force it puts on the pinion gear (the smaller gear driving it). The less teeth on the ring gear, the less force it puts on the pinion gear (the smaller gear driving it).

So if you have a GM 10-bolt differential with a 3.73 ratio and you want to put 400 hp to the ground with 35-inch tires then you’ll need a GM 8.2 axle or Ford 9-inch axle because they have larger ring gears than GM 10-bolts.

Last modified: November 18, 2022