Damaged trans?
i broke my driveshaft at MATS...i removed and replaced the rear sprag...did not think twice about...the 904 drum will not explode like a 727 due to its smaller size..
you can buy the spring and roller kit from bulkpart.com for a few bucks....i replaced the complete assembly with a new one..cause i had one...
several years ago i broke a ring gear on a car with 904....and raced it at the next race...after a couple of passes the trans was making all kinds of noise..the spraq was damaged..