Okay, I’m having a strange problem with my truck’s transmission. It is a 99 Ram Sport 1500 4X4 with the big 5.9. When the trans gets well warmed up, it loses all drive. No forward in any gear and no reverse. It’s like it loses all hydraulic pressure. Leave it to cool down and the trans works fine again, until it heats up. I have checked the fluid and it is full and looks pink with no burned odor. It has probably less than 5k miles on a complete overhaul. I’ve spent hours in online searches, with no luck. Haven’t been able to find anyone having the same problem I’m having. Help!

 

Could possibly be the check valve in the cooler line blocking flow.

 

Who did the rebuild? Any warranty on it?

Next time it gets hot, and stops working, unplug the 8 pin connector on the trans, and see if you get any gears. Keep in mind, it won't be automatic at all anymore. You will have to shift manually, up and down. Also, no O/D, or TCC.