Hey guys, finishing up a 6.2/8hp90 swap into my 70 challenger. Getting to the final stages wiring up the trans controller and finishing up some of the coolant plumbing when I started reading about people specifically in 8hp70/90 swapped cars having issues with the trans case exploding at the tail section down track.

All the failures seemed to happen at higher speed down track, they are all catestrophic failures and everyone reported no vibration prior and claimed their driveline angles were correct (but were they really?).

Almost everyone was using the same setup, a Sonnax yoke adapter along with a driveshaft built using a slip section.

Most of the failures i've seen were in longer wheelbase cars or trucks so some have speculated DS critical speed was the issue, but is it really likely so many DS shops screwed up in making sure the critical speed of the shaft they built was adequate for the application?
Some guys think it was pre-existing damage from the donor car since most of these are pullouts from wrecked vehicles. Possible but seems unlikely to me, especially with no abnormal vibration/noise prior.

Kind of at a loss right now. Not sure if it's an issue with slip sections binding up with pinion movement, the DS somehow leveraging the output shaft because of the sonnax yoke adapter moving the U joint back or some other reason. These transmissions seem to hold up great in 800+WHP 4400lb hellcats so I really figured it would be fine with my setup (about 800whp in a 3400lb car) but this has me worried.


What do you guys think? Thought it would be really fun on the street to have the 8 Speed, also great for some of the roll race runway events they do here but unless I can figure out how to address this I may have to go back to an 80e