Since some time my 400E does not want to upshift as usual (at 1500 with low gas). All other shifts are normal. I tested the solenoid (Kick down) and it works properly. So the reason for late 1-2 upshift (at 2500 -3000rpm) is NOT a stuck kick down solenoid.
I think it must have to do with the valve body (VB) .
Unfortunately I don't know a lot about the details inside the VB but I know the 1-2 shift points are controlled here. I have seen this is a very complicated diagram.
It might be that a spring is broken or a piston does not move?

The 1-2 upshift problem happened over time , started last year with a few late upshifts and has become worse so that now the transmission won't upshift 1-2 normally any more.

Any help or information about the transmission is welcome.

I have a spare 722.3 transmission and I could fool around with swapping the VB but I wanted to hear the opinions first before I do the VB swap.

Martin