OK I have a TH400 in my V3500. I rebuilt it about two months ago. IT has under 1000 miles on it. The other day I added a tranny cooler and fixed a coolant leak. Got in and no more forward gears. It isn't even trying to engage. Reverse works great. Thuds right in and off we go backwards So I am hoping this is something stupid and easy that can be resolved without removing it from the truck again. Any ideas?