I have a 1996 olds lss that has 129k on it. It'* been running great, then just recently I had to drive through a decent amount of water, and rough terrain.. but nothing seemed to damage the vehicle at all.. now about two weeks later, when I drive the car over 30 mph or so, it just revs like it is in neutral. There are no engine codes, or anything. I have tried manually shifting.. same result.

sounds like some water got in the trans. i dont know if changing the fluid will help or if the damage is done

I know I am bringing back this thread, but I am starting this project, and any help or advice is appreciated. Thanks

Are you pulling the transmission out?