Replaced my 88 Pete with a n14 cummins 475 also replaced my trans with a 9 speed running 3.36 rears no pulling power up hill also running at 2000 rpm at 70 can anyone tell me what tranny has to go in this truck to solve this problem my old tranny has ben misplaced and I have no clue what I had please give me some advise thank you and lets keep trucking

A Fuller ten speed overdrive trans, with the "B" series gearset has a .75 to one top gear. That should give you around 1500 rpm at 70 mph, 1st gear is around 12 to one ratio. Nine speeds can be had with similar gearsets if you need a real low 1st gear. Google "Fuller transmission ratios", there will charts posted with the different gearsets available.

your best bet is a 13speed and seeing about changing your 9 to a 13 rather then a new tran. this depens on what 9 you have. a 88 pett very likly you had a 18 and if you dont remeber very likly you never new.

2000 rpm at 70 mph? No power to climb?

Confirm the tach is fairly close to accurate.

I'd confirm the engine is working correctly first. Boost pressure all there? no leaking connections in the intake, turbo to the CAC and back to the intake? or exhaust leaks between manifold and turbo?

Then I'd be wondering the transmission being direct vs overdrive...

Let us know!