[V]

How can I tell if the problems I'm experiencing is related to a bad TQ convertor or a bad transmission?

Vehicle is a 1996 Dodge ram, 2wd, 5.9L I6 12valve Cummins turbo diesel. 77k miles. (Trans was already rebuilt at 30k miles) (Less than 5k miles in past 5 years)

Several months ago, maybe even going back to last winter, when I'd drive the truck maybe 4-5 times a month, the first thing I noticed was that when I started it up and put it in reverse, it would not move. I'd then have to lightly rev it up a few times and then the trans would seem to engage and it would reverse out of the driveway. After that it would drive fine, forward and reverse. It only did that if it sat for a period of time, which was usually 1-2 weeks.

Then back around September or so, while driving it seemed to occasionally have issues with overdrive. At speeds between 45-55, it would almost feel like it would upshift and downshift randomly. When I would accelerate around those speeds, sometimes it would shift up normally, other times it would hang in a lower gear until I let of the throttle, then it would upshift fine on its own.

Now this morning, I had to sightly feather the throttle to reverse, even though I drove it just yesterday with no issues. So then I went to the store and stopped at a stop sign in the parking lot. When I tried to move again, it felt like the truck was in neutral. Nothing at all. But 2-3 seconds later the trans engaged again and I was able to drive fine. I parked, got breakfast, and the truck acted normal backing up and leaving the parking lot. However, once again at speeds 45-55 it seemed to get confused about overdrive again. I got to where I was going and checked the fluid, it was actually overfilled by a decent amount. I know it was at the proper level(hot, running in idle) back over the summer and no one else had touched it since.

I'm wondering if the transmission itself is shot, just the torque convertor or maybe its the valve body. Any idea how to diagnose it a little better?

The issues were never really consistent so taking it to a trans shop would be hit or miss, plus I no longer know of any good trans shops. All the ones now just seem to say you need a full trans rebuild no matter what. Perhaps taking it to a diesel specific shop would be the best idea. I've read that bad grounds or a faulty TPS could possibly cause trans issues on these Rams. If I do need any new parts, I will not go with stock since I do plan to increase my HP level eventually and I know the stock trans wouldn't survive that anyway.