So another one of the many things I'm wanting to do w/my Firebird, and definitely the first performance boosting mod I plan to do, is to swap out the open differential, drum brake rear end, in favor of a posi, disc brake rear end, with a slightly lower (higher #) gear ratio, like a 3.42.

I was thinking the easiest and cheapest way to do this would be to try and find a posi rear axle off of another 3rd gen formula, T/A, or Z28/IROC-Z. The only question I really still have is about how much power they can handle. I'm planning an engine/trans swap at some point, and am not sure which route I'm going, but most likely an LT1 for budget reasons.

Power-wise, I'm aiming at 300-350 crank HP, maybe a bit more later on, it just all depends on what I'm able to invest in this project But basically, I'm just semi resto-modding this car, not turning it into a strict track/drag racing car. Will a stock 3rd gen rear handle what I want? If not, what are my other options? thanks!

 

As long as you only run street tires the stock rear end would probably work fine. If you have any wheel hop then it will probably break. The options are after market rear ends like the Moser 12 bolt, 9 inch Ford, Currie, Strange and some others which start at about $2220 plus shipping.

 

Yeah, that's a a bit more, lol. Well, I'm only planning to use street tires, so that's good to hear! Should I end up having to go aftermarket though, what are the "best" of those options?

 

Aftermarket rear axle assembly, the best?? Well start thinking about $1300/2500+ first.

 

I've sold a lot of Moser 12 bolt rear ends and as far as I know there have been no problems with any of them. I can't say anything about the Currie or Strange rear ends because I haven't got any experience with them.