904 soft shift

Band adjustment......1 1/2 turns backed off on bolt adjuster.
Holding 10 inch pounds on adjuster bolt bolt -- tightened or finger tight-- then tighten lock nut,--Front band **kick down band.
Out side case--drivers side

Low gear +++ reverse band.
2 turns loose after tight.
Inside case under pan---pass, side.

This is very important for shift speed and how hard it hits.

A 3500 stall speed should not make a big difference.

If all is well with the bands then i would think it's the valve body.
Get a turbo action cheetah valve body.