I've just begun to work on the IROC I bought. I did a tune up which made a world of difference, but I've taken it down the road a few times, no tags or insurance. Just to get a feel. Everytime I punch it from a stop or slow roll I get a really loud pop from under the rear. I'm wondering if it's the universal joint or maybe a transmission mount is bad. It cruises fine but if I get on it, POP! Just wondering what you guys think. Maybe it could be something else I don't know about. Thanks.

 

I had a 94 formula that did that. Turns out the front torque arm bolt completely fell out. The torque arm was slamming into the bottom of the car every time I would "get on it". I'd check that first, it's your cheapest fix ($0.50 bolt).

 

99.9% of the time, that noise is due to a broken trans mount. If that ends up being the problem with yours, do yourself a favor and buy an Energy Supension polyurethane mount. They're only about $22, and they're Wayyyy stronger than the pathetic GM rubber mount. You can also get their polyurethane torque arm mount while you're at it for another $15. It should only take about an hour to change out both, and your car will thank you for it!