I have a 99 V8 Durango with 123k mi on it. The trans. fluid was flushed last week and this week when I was driving it wouldn't shift out of first gear. I drove home at 4k rmp and 15mph. Took back to the gar that did the flush and they said 7 comp. codes came up. Reset comp. Govn pressure sensor codes still came up and this was replaced. Car still won't shift. What could be the problem?

try speed sensor at the rear of trans

i had the same problem only mine only done it when it was low on gas ..like 1/4 tank or less.. and like he said i replaced the speed senser at the rear of tranny and wala problem fixed... it killed me for weeks trying to figure it out i was told 100 times it needed a 2 grand rebuild...it was 18 bucks @ autozone
good luck