I recently finished a rebuild of a A500/42RH. (OD+LU)

TransTec overhaul kit / new steels and Alto clutch plates.
TransGo Reprogramming Kit
Billet accumulator piston

Now during operation I've found a couple of things;

- Engagement from P or N into 1st gear feels fairly normal, maybe a tad soft considering the TransGo kit being installed.

During normal driving;
- 1-2 shift feels ok, 2-3 shifts feel nice and firm.
- shifting to OD comes in nicely, Lockup is nice and solid. (Both manually controlled with dash switches)

During firm/hard acceleration;
- 1-2 feels soft
- 2-3 very noticable flare up in the engine rpm. As if 2nd gear/band releases to quickly, or starts slipping as soon as the shift-operation is started.
- shifting to OD comes in nicely, Lockup is nice and solid. (Both manually controlled with dash switches)

Adjusted the front a quarter tighter to 1-3/4 turns out, from 2 turns. Helped some but not much.

When accelerating hard in 1-2 and get off the throttle very briefly when trans shifts to 3rd, all feels fine.

Engine in front of the transmission is a 360ci with a mild (Comp XE256) cam. Nothing serious.
Transmission holds WOT-power in all gears, no slip, leaving me to believe this is a band/accumulator issue perhaps?
There's a 3.8 band lever on the front band. I'm thinking a 4.2 lever would provide a little more clamping force?

After support contact with TransGo, did a light mod to the TP-linkage. Slight improvement but not much.

Accumulator port-pressure is 75psi in D and both manual 1 and 2.
Pressure rose when upping the rpm but couldn't test max pressure increase because of single handed in-car operation.


Any tips, things to check / look up?
Hope to be able to solve this with transmission in the car as it's a bear to remove (A-body + headers).