If the sprag lets go, the drum will spin at 2.2 times the engine rpm
So if it lets go in say the water box at 7k, that is 15,400 rpm... and the reason i said 15k in my post.
TCS has tested various drums.
Stock drum let go at 14,000 rpm
Steel drum 25,000 Rpm
Aluminum drum 36,500 rpm
Cars see 7 k a lot, sprag failure at that or anywhere near it results in the drum turning very fast in the opposite direction( over twice that speed).... equals not good. And lots of the parts in these trannies are 50+ years old, so might not hold as much as test results would suggest
