I have an 05 chev crew cab duramax allison. I got in my truck yesterday and put it in reverse and hit the throttle. Truck wouldn't move for 5-10 seconds. The truck had been sitting for a couple of days. This has happened a couple of times. Any thoughts??

Oil drained out of pump or converter maybe. Next time try letting it sit a minute before putting it in reverse and see if it still does it.

My brothers 03 does the same thing. He mostly notices it when he returns to the airport after is sits for a few days. I think i remember seeing some posts here before about some check valve not holding. Maybe one of the guys in the know can confirm this. Mine will delay some going ito reverse, not nearly that long though, every now and then. Mostly I have noticed that when I replace the spin on filter after is starts doing it it goes away for me.