So it started when I was heading to a job in new mexico I made it all the way to abilien texas pulling my camper the truck started feeling like the tranny was slipping going down the highway. I would be driving along and the rpms would shoot up real high with now power id jave to let off the fuel and it would stop then it would just keep doing it. I took it to a tranny shop that morning they checked it out the tranny was fine but it had thrown low fuel rail pressure code. I vhanged the fuel filter and finished my trip no issue a few months later i noticed that when I get on the truck pretty hard it will do someone of the same thing where the rmps will just go through the roof but it wont have any power and ill have to let off the fuel for it to shift out into od . this is my first 3rd gen not to mention my first auto diesel ever and I'm lost I jave awsome boost pressure when I get on it the boost pressure gets up to 32lbs

 

No expert on 3rd gens or auto tranny at all but if the rpms are shooting up and not your speed something is slipping in the drive train. 

Could you fill out your signature so we know what we are working with exactly. 

 

Most likely the torque converter clutch is failing or the clutch packs in the transmission are done. Assuming 48RE...

 

@Dynamic is a site transmission guru.