shifts from 1-2 @25 mph,2-3@38mph (only when I lift off the acelerator) and then @ 45mph will go into 4th if I let off the gas, otherwise it would red line and who knows what then.Would the speed sensor cause something like this or is there another electronic control in there to look for? Seems very hard to find service info for these old transmissions. Overspeeds 1-2,wont shift2-3 unless you back off the throttle and same for 4th overdrive . Did drain out 4qts fluid once then 500miles did this again with same results. Anybody know what could be the problem here?

 

Always suspect the "throttle position sensor" for symptoms like this.

It is DIRECTLY involved with shifting characteristics of the transmission.

Can be tested and not too expensive to replace.

 

heavy foot? lol could be the torque converter maybe