Transmission controller problem

[imbvl]

My '01 X5 4.4 85K miles had a BMW-rebuilt tranny installed by an independent shop - very competent people. A few weeks later, it developed a problem: if I leave a stop in a hurry, it starts in 1st gear, instead of the usual 2nd (as it should). It revs to 4K or 5K rpm, then goes into neutral. Pressing the accelerator causes it to over-rev, in neutral. The only way to get it to up-shift is to shift the lever into neutral, then with foot off the gas, shift back into Drive. Then it will accelerate normally (in 2nd, then 3rd, etc.). I haven't played with the 'manual' shifter mode. I think I did, once, to try to 'manually' shift it into 2nd - didn't work.
I bought it used (80K) and when the tranny went bad a few months later, I asked to dealer to 'comp' me a rebuilt one, for 'good-will' - I've owned 8 BMWs since 1980, most of them were serviced there, and 2 were bought there. Anyway, they declined. Thus the rebuilt, purchased wholesale and installed by the independent (Auto Sleuth, in Jupiter, FL).
When it developed the shifting problem, I took it to back to Auto Sleuth. They verified that the oil level was correct (thus no leaks), read the fault codes, and told me the problem was in the transmission control module inside the transmission, which was included in the rebuilt tranny. They said it was a warranty problem for the dealer.
I took it to the dealer. They read the fault codes, and said it needed a transmission wiring harness, and a new shifter selector switch on the side of the tranny, both of which were from the original transmission - $1300 including parts and labor. No warranty was to be applied. I declined their offer, and took the vehicle back.
It doesn't seem likely to me that an external wiring harness will cause the tranny to lose its way, and not be able to find second gear. It also seems unlikely that an external selector switch will have any effect, since the transmission shift lever is never involved in the failure - it only happens when I accelerate briskly, both hands on the wheel, no gear-shift involvement. It seems the dealer's techs want to read the fault codes, replace parts, and charge me $1300, but those steps won't address or solve the problem.
HELP! Anyone have any ideas?
My next step is to go back to Auto Sleuth - they're run by a VERY GOOD diagnostician. But I'd like to understand the problem, myself, first.
Thank you!
Bruce in Florida

[imbvl]

Update:
I took it to the dealer. His Fault Code reader said the transmission shifter selecter switch (on the side of the transmission) was suspect, as was the wiring harness. Mike Miller at BMW CCA sent me some info on a recall of that switch, which described that in a failure, the transmission could shift down, but not up. So I bought a new switch from the dealer, put it in, and fixed the problem! HAPPY!
Bruce in FL

[ahadi]

Hey Bruce,
I have similar problem as you discribered it above about the shift lever after the car has been driven for about 45 mins. I still have the original tranny for about 125K miles. can you tell me the part number and the cost of the "Selecter switch"?
Thanks
Hadi

[imbvl]

Hadi, the 'Position Switch' for the transmission shifting is part number 24-10-7-512-755. List price is 277.78, net is 222.22. It was very easy to install.

Bruce

[ahadi]

Thank you for the info. I will first get it tested by the dealer.