n20mstr- I suspect you have forgotten more than me but I spoke with a real good local driveline shop recently that did drag racing stuff- He said driveshafts do wear out. I don't know your power level but 500 passes is a decent number and it could be that it twisted and is now out of balance.
Its a small block duster street car . 400+ ? Hp . Runs 11 teens at 120. I think It’s the tires. I also think the driveshaft needs maintenance. It’s been in the car for ten years . He races multiple classes most times and like I said it’s got well over 500 passes on it most of them 11.50 to 11 teens . It’s a 3200lb street car . It’s got some street miles on it also .
