Problem Downshifting After Rebuild & TCS Replacement

I have a 96 dodge ram 1500 with the 360 auto trans. I just had the trans rebuilt a few months ago and im having a problem with it down shifting after it has been driven about 30 or 40 miles when it does this it will not even manual shift into first. it will go to 2nd and then shift to 3rd.

I have carried it back to the trans shop several times and I think at this point he does not know what else to do. Yesterday I picked it up for the 4th time after he changed a T.C.S. (i think that is what he called it) thinking the would fix it and it has not. I really believe the guy done a good rebuild job but we have no idea what else to check it really seems like an eletronic problem. Do you have any suggestions ?