A few questions for anyone who knows. Does anyone know how much horsepower the 4th gen rear ends can handle? Is it the axles that are the main concern in a factory rear end, or does something else in it break first? I found a 4th gen rear with 3:23 ratio and FORGED Moser axles. I am wondering how well this would hold up to a 550 to 650 horsepower engine. Thanks guys!!

This isn't a specific answer to your question; however, the fourthgen rear will handle no more power than a thirdgen rear with 28-spline axles.

JamesC

Perhaps I need a Strange rear end, if I'm planning on making 530 to 650 horsepower at the crank, or would just having forged axles be the key?

No. get the Strange rear. i have broken 2 junky 7.5 rears. One in my third gen with street tires and on in my 2000 SS M6 car. Don't waste your money on any 10 bolt for our cars. Go for a strange 12 bolt or S60.

I never saw the s60 before now. I just checked it out. Looks perfect. Do I need the abs thing with it, for an 86 IROC? If so, which do I need? I don't quite know what the 3 channel and 4 channel stuff is all about. Thanks guys, for your input.

you dont have ABS in your car so you wont need it.