[kwmech]

Switch inside the pan, or it somehow got unplugged internally. The switch does not control the shifting on a T400. It just controls the down shift when you stab on the pedal. (If teh governor is working correctly) Early up shifting could be a vacuum modulator out of adjustment, a small vacuum leak in the hose coming to the modulator or the governor out of calibration. I've seen the rear bushing in the trans walk out of the case and strip the nylon gear on the governor rendering it useless. Pull the 4, 5/16'' bolts out of the small steel plate (3x3) near the back of the trans and pull out the governor. You will have a slight amount of oil come out. If the gear looks good, look at the valve internally and see if it goes up and down when you move the fly weights.


If all that looks good, then move on to the vacuum modulator for an adjustment.


Actually try adjusting the modulator first, pull the vacuum hose off and with a small flat blade screwdriver go inside the hole and tighten the screw about a 1/4 turn then take it for a drive and see if it makes a difference, repeat as necessary. When you pull the hose off and get even a slight amount of trans oil, you've found your problem, replace the modulator then adjust