I am getting ready to have my 3rd rear quarter glass (Passenger side this time) replaced. The first and second one came after hitting the gas a little bit around a left hand turn and torqued the car enough to crack them. This time I thought I was pretty safe, full strut tower braces and much more rigid car, broke another one after a little goose around a left hand turn. Anyone else have this happen? My car is pushing near 400whp and 385lb of torque. Anyone else on that body with the same horsepower? Dealer has said they have never seen it and showed me several sti's they had with many more miles on them. Wondering if it is just something I have to live with with this much torque on the car. It's frustrating because they always scratch the hell out of it trying to get the windows out and I have to follow it up with interior and body work . (The first time the glass people actually used a razor to cut the interior trim away, was a mess)
I really don't think that's normal... I don't have quite the power you do but I'm still pushing 360ish torque. I don't see how that power can even make the body flex enough to just pop the little windows in the back, I feel the rear window would really be the one seeing all the stress.
Maybe try some rear diff bushings... You could just really be jarring the back of the car if that diff is really clunking.
Have you thought about plexiglas glass or lexan? I don't know about getting them cut and fitted or price but I know we use it (plexiglas) in the army in our aircraft because its a bit more flexible than glass.