Quote:
Originally Posted by TCMoto
Thanks for the replies.
I'll plan on just replacing the whole actuator. I plan to keep and drive this X5 for a long time and I've already made a lot of repairs on it. The BMW gear repair kit is $100 and a Bosch OEM actuator is $400. The gear replacement repair doesn't seem too horrible but just bolting on a new unit will be much easier without the concern that I didn't do the gear correct. Is it possible for the resistor on the actuator to go bad? Should I replace that as well? ...
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The classification resistor is to allow for "calibration" of the X-Drive system (and is selected/setup in the factory assembly line). Which leads to the assumption that if you change the entire transfer case, you need some way to select the correct classification resistor.
BUT, it seems that many folk have replaced the transfer case, paying zero attention to the classification resistor, resulting in a working X-Drive system. The reverse is also known to be the case (a bad classification resistor replaced with a random replacement, with good results).
Replacing the actuator unit only should not require replacement of the classification resistor.
The BMW TIS states: -
VTG actuator motor with incremental sensor and classification resistor
The VTG actuator motor (VTG: transfer case) opens and closes the multi-plate clutch. The location of the actuator motor shaft and the adjustment rate are detected by the incremental sensor.
The classification resistor ensures that mechanical tolerances in the transfer case are considered. Optimum function is thus ensured.
Classifying resistance:
The locking torque characteristic curve of the multi-plate clutch may vary slightly due to mechanical tolerances during the manufacture of mechanical components.
The actual characteristic curve for a transfer case is recorded by means of clutch test stand after assembly. This characteristic curve is compared with the characteristic curves stored. The best possible characteristic curve is selected.
Each characteristic curve stored has a classification resistor as an identifier. After completion of assignment the classification resistor is installed on the transfer case.
In the vehicle, the resistance value is imported from the VTG control unit. The software automatically sets the established characteristic curve. This setting is made whenever the engine is started or is checked whenever the engine starts.