Trans Help

Bought an 01 X5 3.0 a couple of months ago. After a month it started shifting hard, seemed to rev higher before shifting and acts like it is slipping. Took it to a BMW repair shop. They told me there were no codes but suspected the TQ was going bad. Read on here that this is a common issue with the E53. Didn't want to pay the $1600 price tag for a new one so bought a rebuilt unit and had a friend's shop install it. Picked it up yesterday and it still has all symptoms. The technician is indicating a possible problem in the tranny or the computer module. Any advice from anyone? I've already sunk $1100 for a TQ and am hesitant about sinking another $4000 or so for a tranny to find that isn't the issue either.