Generally it is just the transmission that is the weak link other then pistons. Pistons become the issue when KR is present, otherwise the bottom end is pretty solid. Only in rare cases will the bottom end fail if KR isn't present. This is of course just from what I've read/learned from 3 other grand prix forums: gpona/grandprix.net/clubgp.

Transmissions tend to head south when you get over 300HP. Even small changes, a hardened input shaft and a higher stall torque converter helps a lot. Pistons will go bad any time you have prolonged KR. Most of the time that comes from people over boosting, and or not scanning the engine. If you watch what'* going on, and actually deal with issues, the engine should be safe. And most important, boost is not power, air flow and timing is.

Thanks. I need the HD trans anyway because I plan on doing a lot of mods over the next couple of months. Wouldn't help to be on the safe(R) side

What transmission is in the car now? A 4t65e? If so, then all you need is a HD diff, HD diff cover, and a new passenger side axle. That'* about it. Wont hurt swapping the output shaft.

I wonder if pistons are safer in the L32? I know they have powdered connecting rods, and the heads are opened up a little more.

Also about the transmission, I've heard that 300whp is the limit that the stock trans can take too, however my transmission went @ 84k miles even without beating on it. I however did get the car @ 56k miles so I have no idea if previous owner abused it. Just be ready if you mod for the transmission to go any day at any time without warning. Mine went without warning in a parking lot. I got into car, backed out, and it wouldn't go into drive. Found lots of fun metal in the pan.

The number one killer of these transmissions is the burn out while turning. One wheel burn outs kill the diff, even a HD diff. Also, low profile tires are a killer, no give when you floor it, just a nice hard snap.

So if my tranny feels like its slipping through the first and second gears, what is the cause of that

either need a flush or a rebuild. clutches may be worn out

Could also be a blown O ring on the 1-2 shift modulator. Does is only slip on 1 and 2?

A buddy of mine told me the same thing, that it might be the modulator. And yea it only does it on 1 and 2. Once its in third or OD(or the correct speed during auto) its fine. How would I check this