trans slippin really bad
 

I warmed my cummins up before leaving work. Got in and put it in reverse and nothin. Put it in drive and it was fine. Checked the tranny fluid and it was a little low. I added some and went to drive home and it started acting real funny and slippin real bad and just didn't want to go anywhere. I checked my tranny fluid when I got home and it was over full but wasn't like that when I left work. Was the reason for the slipping because it was over full or what?

You checking it with the truck in neutral?

No I had it in park. But I have just heard the pump doesn't run in park. So yeah its over full