Was driving in town yesterday and the cel came on then the truck sounded like it had a fuel knock and had zero power. tranny shifted perfectly fine and engine ran great before but then the tranny shifted hard, only revved to 2k, and had very little power. I let the truck cool off for a little and then it was fine. After a few minutes it happened again. Let cool off and then again. After each time it happened sooner and sooner. It got to the point where it wouldn't come out. I assume it's limp mode but i'm really not sure. I changed the fuel filter drove fine for a few miles then started acting up again. Really just looking for some opinions I'm new to duramaxes so I'm sure you guys know much more than me.

 

Check the wiring harness to the tranny. There's a seal of sorts when it goes trans fluid will find its way into the wiring harness. It will saturate the connections.

 

any codes?