Auto trans 46re issue

First things to check- fluid level idling in neutral warm and condition of fluid. If the fluid is still red and low, try filling to the full line and retry. If the fluid is brown/ black, that is a totally different story. I have rebuilt so many of those at the dealer that I ended up buying my own tooling for them. The weak link is the overdrive piston, and once that seal goes, it just starts eating stuff up if you don't catch them in time. Check your fluid ASAP