@XOLATEM the drum shatter was a tuning/ heavy foot issue.
We bought the truck from a good friend of mine which had just had the transmission rebuilt a few hundred miles earlier. Shortly after buying it I installed a php hydra chip. I asked him if he had a modified valve body installed when he had it rebuilt, which he told me that he didn't. I installed the tunes for a stock valve body.
Fast forward about 6 months. I pulled out of a parking lot and noticed the long winded stoplight down the street was green so I floor it trying to make it and it down shifted to first, sounded like a shotgun went off under the truck.
Had my buddy I bought it from tow it to my shop, tore the trans down to find three valve body bolts backed out, the center support bearing non existent, and the forward drum shattered. Also found a transgo tugger hd2 installed in the valve body.
So I blame the failure on the center support bearing failure and the fact that the line pressure was way too high with the shift kit running on tuning for a stock valve body.
Only thing I did was replace the forward drum with a cheapo from ebay, center support bearing, install tunes for the modified valve body. Have put about 95k on it since with no more issues.
James