[Mike L.]

P1720 is solenoid A ( trim solenoid ) control clutch stuck off. This means you might have a faulty output speed sensor ( rare ). More than likely you everpowered the C3 cutch in 5th and you limped the Ally. This code will cause the Ally to default to the next lower gear. Too much power.
mike

 

[Mike L.]

Converter flow valve knocks down mainline pressure anytime converter clutch is applied. No matter whos valve body you use it won't help with a stock converter and high horsepower.

 

[Mike L.]

Pat
No problem. I think it all depends on how you use the power and not how much you have. As far as the Allison stock converter, I agree that the unit is solid with exception to the TCC piston design. There is nothing to stop the piston when the clutch applies and the center actually comes down a little too far giving you a ( stepping on a frisbee affect ) and causing the inside portion of the clutch to burn and the outside to hardly touch at all. The engineers at Allison admit to this. If you do not have a solid lock at the converter clutch your trans will not live.

 

[Mike L.]

I think you are beyond a valve body. '01s have other internal issues that need to be addressed along with high performance mods. I would go with a name brand triple disc converter to start with, and some pump, clutch and valve body mods. At this point I'll let the vendors jump in.