We have a 2004 dodge ram 2500 diesel, shorted out ECM, got new ECM and now the transmission is not shifting properly(changed ECM 3 times, because we thought it was the ECM making transmission not shift) . It won't get out of first gear. IF it does get out of first gear it will take off in second gear and shifts like its supposed to. Took it to a transmission shop, they did diagnistics, they found nothing, they suggested to take it to an auto electrician?.. Any suggestions on what could be the problem?

What did the trans shop do for a diagnostic? Do you still have reverse? If first and reverse are out, then you have internal damage and need a rebuild of some kind.

Yes still has reverse. The issue is it is hard shifting out of first gear, If/when it does get out of first gear then it shifts just fine. The transmission shop hooked it up to their machine and went through all the gears and they said there was nothing wrong with the transmission.

If it's in limp mode, there *should* be codes stored in memory. You should have a p0700 and CEL on, and then transmission codes in the TCM.

I'm having a similar problem at 20-30mph. Won't shift into 3rd unless low rpm. Just hangs there in between gears and rpm's race up. Is this called slipping or something?

Did a search here last week and a few people mentioned that the battery posts and grounds need to be cleaned-up for a possible solution. Something else about moving a wire around the alt which might be interfering with stuff. I'm no expert though. I'll clean mine up best I can but will keep searching through the forums. Hopefully someone can point us in the right directions.