I have a 87 Chevy truck with a 383 stroker and a 400 turbo trans with a 3500 stall torque converter. Is there a way to adjust trans to shift at higher or lower RPMS. The trans doesn't seem to change more than once. It changes smooth and it is possible it is changing into second as soon as it starts off. The rear end is geared very low or the trans isn't shifting into the highest gear. I have been told the modulator valve may have been adjusted or changed to make it shift this way. I appreciate any help anyone can give me.