Quote:
Originally Posted by Sophisticated Redneck
As mention above but it seems to be if ignored: Check your transfer case.
Here is what happens when your transfer case goes out of calibration:
The DME asks the transfer case to set a certain torque within the internal clutch packs in the transfer case.
The sevro motor in the transfer case responds and adjusts the clutch packs.
The DME then looks for a very small percentage of acceptable wheel slippage between the front and rear tires.
If this is not within spec, the DME tells the sevro motor to release all pressure on the transfer case clutch packs and start over.
This entire process happens very quickly and will get stuck In a loop if out of calibration.
The rapid engagement and disengagement of front wheels creates a "tugging" or "missing sensation" that can happen at any speed.
Many threads on how to fix yourself: 30min transfer case oil change plus ISTA to recalibrate or some foxwell scanners can (530 can If memory is correct)
BMW techs are not trained to test or calibrate transfer cases. If you are not a DIY person, you MUST specifically ask them to perform recalibration test. Most will just want to sell you a new one for 8k when a simple oil change and recalibration will fix.
F15/16 owners get screwed that most transfer cases now don't have oil drain plugs so you must siphon out. Some dealers refuse to do this and just want to sell you a new one for 8k because $$$.
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You mention "at any speed". Our X6 only seems to have this symptom when going up hills. Battery is fine, I have a CTEK - 40-206 MXS 5.0 I use to check and maintain it. I have new plugs and coils, had all typical fluids changed, made sure car has most current software. I can mention this to my independent tech. I don't have an extended warranty, now wishing I did but of course we didn't notice this until our warranty was up.