e36 m3

Hey all, I bought an 06 TL with 68k miles with a bad transmission described by the seller. Upon driving the car back home the car would drive okay for 5 mins when cold and when hot it won’t move it feels like it’s in neutral it will occasionally drive but not all the time. I was able to place a scan tool on it on my way back home and pulled up with p0741 and p0722. I purchased this car thinking it just needed some solenoids swapped and a new torque converter. All the solenoids were tested and checked out fine reading correct ohm specs within range so it lead me to believe it was a torque converter issue. I did a transmission flush and clean the solenoids filters to see if it would help but didn’t do much. I decided to just pull out the transmission to swap the torque converter. Since the transmission didn’t have any jerks or loud thumps I figured it wasn’t the actual transmission that was bad but the engagement with the engine. Upon removal of the transmission I noticed it had already been replaced before with an 05 transmission. I ran the vin plate on it. While removing the transmission, I ran into this forum and saw people mention the av6 swap so figured while I’m at it might as well upgrade the transmission. I found one at my local lkq pick your part and scooped it up for a good price the donor car was in an accident so I assumed the transmission was good. The swap goes well and the car is put back together the next day. Everything works no clunks no check engine no leaks everything is topped off and in spec. I go for a test drive and the car worked! Everything was working well for about 20 miles, i started to get little bit worried and skeptical because I noticed the car shifting a little bit late at times close to 3000 rpm’s. Well long story short it starts having the same exact issues and symptoms from the old transmission removed a few days back. No blinking d Light or check engine whatsoever. I got the car towed back home but I am going crazy trying to figure this out. How is it that I replace the transmission with a better transmission just to have the same exact issue occur in a matter of hours. There has to be something more to it, is it the ecu? the wiring harness. At this point I have no clue what else to look for.
It feels as if the transmission isn’t being cooled enough causing things to overheat and not operate properly.

any help would be great appreciated before I scrap this thing and accept my loss.

stokesey

See if you can scan the transmission codes. They don't show up on an OBD scanner, you need someone with a more sophisticated device. Dealer could do it or an Indy with a good scanner. It MIGHT be possible to scan those codes using a paperclip in the OBD port and counting blinks on your dash, but be very careful not to short your computer out. Read up on the clip trick online, I don't have time to post it.