Mechanic says my 2003 sedan has a bad Valve Body. He's looking for an after market part.

I'll have 2 choices, try to find a Valve Body replacement or replace the Trani. What years will work for my 03; since I have the opportunity to do this right the first time, any suggestions from the pros out there???

Thanks...

Although I think we have found the problem, maybe some of you guys out there could advise different. Car was reving high in 5th gear and could not make it up steep hills. Had to shift into tiptronic at which point car indicates it's in drive (not manual) and drives in automatic. Got the car close to home, but stopped for a coffee first. When I restarted and put it in reverse, the trani would not engage; had to push it back and then drive forward, car jammed into first once going all gears are slipping and had to drive in manual again. Took it straight to the mechanic. Tried reverse again when I got there and this time it worked. Trani worked perfect before this day.

Anyway, I know nothing about trani's. My mechanic is a good guy, has been really taking his time to source out the problem and solution (no charge)...