A few days ago I made this post (about my tranny not shifting into 2nd and 4th):
https://ls1tech.com/forums/automatic-transmission/178151-4l60e-wont-shift-into-2nd.html

Took down the tranny yesterday and the Kevlar Band BROKE!!!! It didnt burn out, but snapped at the rivets! This was on 10psi boost. In process of putting the tranny back together and will be posting dyno and track results soon.

 

What band was that? Was that a Raybestos? Same exact thing happened to me a few months ago. I've never sprayed or launched on stickey tires since I did the overhaul back in October either. So pretty much stock HP, with a Yank SS3600 and street tires. In fact, it was raining the three days prior to it's failure, and the day of it's failure, so I wasn't even beating on the car when it happened.

Just curious to see how many other people had the same problem with that band....

 

What kind of Servo are you using? Many people like to use the "Billet" servos but I have had to many bands bust as a result of the overkill created by the Billet servos. I have yet (knock on wood) to break a band with the Corvette Style Servo. The Vette Servo gives you everything you need in a Servo without the "overkill".

Could also just be a defect band.

 

First, you did not break the band due to horsepower. I agree with Team Tripp, the billet servos are overkill & not needed. Use the Borg Warner Hi-Energy 2-4 band with the Corvette servo along with the "modified" Trans-Go Peformance Shift kit, and this should work out fine. The Kevlar band does not have the holding power that the Alto Red or Hi-Energy material do.