what controls the shifting of the trany? is it the BCM or PCM? reason I am asking is it seems that my tranny is not shifting correctly and my initial thought is the previous owner may have programed something other than stock into the computer.


the symptoms are when initially driving off (usually when cold) it seems to "pulse" under light throttle pressure but appears to run normal when I get on the gas a little harder. I also heard from a mechanic that works on jeeps specifically state that he feels the tranny shifts too soon, which is what led me to this question.

 

Actually it's the Transmission Control Module (TCM), but it gets info thru the data bus from both the BCM and PCM. The PCM provides speed, throttle position, vacuum and rpm info. I'm not sure how the BCM gets involved, but the CCD data bus is complex. I do know if you move the jeep with the door open, the chimes will drive you crazy.

Reading back in the post, you have a 96 so you don't have the CCD data bus, but the TCM still controls the 2-3 and 3-4 shifts. The 1-2 is controlled by governor pressure, speed, and transmission throttle cable.