how long will a 4 cyl rear end last behind a 5.0 with a aod. i got one with 3.73s in it free and i didnt know how easy it would break. was going to put it in while i rebuild my 8.8
Depends on how often you beat on it. Not very long, but if you beat on it a lot, it'll be a race to see what blows first: your underbuilt rear or your AOD. Anyone want to place a wager? My money's on the slushbox.
Depends, of course, on how you drive, and on how much traction you have -- if it won't hook, the tires become the fuse that saves the rest of the drive train. Those of us with conversions like mine have found that the Dana rearend in the Volvo's (7 3/4") seem to hold up pretty well -- largely because the biggest tire you can get under the back end is a 225. As long as the tires spin, the rear end seems to survive.
I don't think you will have any problems with it unless you get a power adder AND traction. The 7.5 has the same axles as the 8.8... the weak link is the spider gears, which don't cause catostropic failure like an axle would/could.
I have heard of people running 11's, but that is on borrowed time.
And what a weak link those spider gears are. I blew the 7.5 in my stock '84 GT (about 175HP new, which it wasn't), and spit them right out the back of my '79 Capri, which was a 3spd auto inline 6 (even less) Both cars running relatively stock suspensions, most definately no power adders, and I'm not one of those guys that lays strips at every stoplight. I can only imagine how long it would hold up behind the EFI power in a '91 with it's bigger wheels. It will work, although may have to swap some brake lines around a bit; just don't take your sweet time rebuilding the 8.8.