Shifting problems, shifts too early/rough downshifts

[Hotrodx199]

So anyway we've been told by a local mechanic that there could be a vacuum leak which is why he told us our car runs at 1500 when you first start it up for like 20 seconds but we can't seem to find the leak, could this be why our tranny shifts wrong?

Anyway to the tranny, when you're driving lightly in town it will go into overdrive as low as 30 mph, i think once at 25mph. When this happens and you come to slow down it's really rough and the car vibrates because the torque converter is still locked up from the overdrive. When you put your foot into it a little more it down shifts like 2 time really rough from going to overdrive to like 2nd. Tach doesn't function right so i dunno where the rpms are at, but it's super low bogging the motor basically.

 

[92exp4x4]

Did this truck get a new tranny recently?

Pull codes, the 3-4 shift and TC lockup are controlled by the PCM. You may have a bad speed sensor, or other problem. Also check the modulator valve on the side of the tranny. It is a vacuum controlled valve. Pull the line off and check it for tranny fluid, if it has any in it, replace the modulator.

There is also an adjustment procedure for the kickdown cable on the trans. I'm not totally sure what it is, but on the other trucks i have it goes as follows: have a helper pull back on the cable/bellcrank assembly at the trans and at the same time, pop a clip loose at the throttle body. The cable will go to the correct length and you re-clip the connector. I'm sure the Explorer is similar (Only one of mine is an auto and i have never had any problems with it...yet).