New to this forum to hopefully get some help

I bought a 2012 535I GT about a year ago with ONLY 50,900 miles. It had a slight shudder at low speeds. Dealership updated software, transmission new oil and pan, and reset adaptations. no change
It also had the oil cooler leak. Thanks to YouTube I fixed myself, and saved $1700.. wasn't too hard. (yes I also changed the belts, tensioner and idlers while doing this leak)
The alternator was acting up. low and high voltage, so I bought a remanufactured one. figured the oil leak onto it pre matured it.
I changed the vanos, coils, plugs MAP and PAF sensors. Still a slight shudder.
Tires new so not that.
Finally came across a thread regarding the transfer case and fluid. So I flushed it twice and the car drove great. much better. no hesitation shudder at low speeds.
So brought the car back home, lifted back up to put the skid pan/shield back on and figured while under there give it a good clean. was a bit dirty.. finished up let dry and then started the car and instantly got the 4x4 dash light. pulled the scan tool out and indicated 440101 VTG End of transmission service life. So thinking it was an electrical problem, back under the car inspecting and drying. no change.
Took to BMW and they indicated needed new VTG. I doubted this as it sure seemed 100% related to the cleaning. new VTG is $2000 CAD and $2500 repair bill. So I found a used 20,000 mile VTG from ebay for $450. Dealership installed and programed.
Car drive just fine for 3 weeks and all of a sudden bam. dash warning 4x4 stabilization and pulled the OBD code of 440101 again. WTF. no way this VTG is toast. NO water, NO hesitation, No noises. car driving fine and when shut off and back on after a 2 hr drive the warning came on.
I'm thinking it is a communication issue, not a mechanical problem
Thoughts?

I also had to change my alternator a few weeks back because the reman one was not working right voltage regulator. high and low voltage spikes. (of course 1 month out of warranty)
BMW tested the system and said needed a new alt. so I bit the bullet and ordered a new OEM one for $1535. ouch. last weekend ( a few days after the 4x4 stabilization returned) the car dash warning came up, car not charging.
Pulled to the shoulder, shut the car off and started it back up and that dash warning went away. pulled out the diagnostic tool and saw 6 new ECU error codes all related to LIN/BSD communication. like no alternator, no coolant pump no oil level sensor. (one system that I have read)

So did/do I really have a VTG and Alternator issue or is there other gremlins being overlooked.

Extremely frustrated.

 

I would clean the connects with electrical spray. Then test voltage coming from the alternator. It seems there's an electrical issue but you have to find it. Do you have ISTA to assist in troubleshooting? Do you have a voltage meter or an OBD reader/ battery tester so you can view the charging voltage? As of now I would table the VTG.

 

The alternator is currently charging and the connector was cleaned this morning with a chemical spray designed specifically for electrical wires/terminals.
the BSD line and ECU were disconnected and proper ohms present. So a glitch I guess.

The BMW shop indicated the TC oil was quite dirty ( and I changed it 2 months ago) so by this condition they determined it needs a new TC. They could not clear the 4x4 VTG 4401001 code by resetting
they quoted me just over $10,000 to replace the TC wholly hell!!!!

Should I get a new opinion?
Used or reconditioned TC is like 1200-1500 and I could likely do myself.

I wonder if the drive shaft ratios match. was a service bulletin on that issue/mistake BNMW had. they wont likely warranty that miss match.

sucks for such a beautiful car with so few miles it needs this type or repair.

 

If do remember there were 2 different ratios that came on this car. Double check the right one was put on. I would think they would of checked to make sure before installing the replacement. If that was your initial issue you may be need a new differential which is labor intensive.

 

Hi there. Did you ever get to the bottom of this issue please? We've reconditioned our transfer box, this didn't fix the issue. So we've replaced the transfer box with another used part. We've replaced the VTG module 2 or 3 times and we cannot for the life of us get this fault code to clear. We've recaliberated the VTG module numerous times. Still won't go. We also have a voltage fault, we so too are wondering if it could be alternator related. If you could let us know if you managed to get to the bottom of this issue it would be greatly appreciated. Thanks