Good evening all, or whatever time it is where you are!! Just have a quick question for anyone in the know.

I've never had a vehicle with an "auto 4wd" option, and I've been kind of apprehensive using it. Not that I would select any variation of 4x4 on dry pavement conditions, but as winter in Michigan is inevitable, I figure I should probably figure all this out now.

I've been doing some research on the auto option, and from what I can find, it engages based on the ABS sensors. Considering that my ABS light has been on since I purchased my beloved money pit, should I not even think about using the auto 4x4 feature? Thanks in advance for any responses and have a wonderful weekend!

 

The Auto4wd system does not use the ABS system to detect wheel slip. There is a front and rear speed sensor on the transfer case itself that the TCCM uses to detect axle slip. As such, having an illuminated ABS light should not affect the operation of the transfer case.

Basically, when Auto4wd is selected, it engages the front axle and waits for slip to be detected. Once slip is detected, the TCCM will applying more load, via the encoder motor, to the front clutch pack, sending more power to the front axle. The encoder motor on the Auto4wd equipped transfer cases has an integrated brake on the back of the motor that will lock the setting of the clutch engagement so it can vary engagement from 0-100 (or nearly zero as the clutch is preloaded) to 50-50 front-rear.

Given that there is an electronically adjustable clutch in the front output, this transfer case can be driven on dry roads while in Auto4wd mode without issue provided that the system is functioning properly, transfer case fluid condition is good, and the proper fluid is in the transfer case. That clutch requires GM Autotrak II fluid to perform properly. Regular ATF can cause the clutch to bind too much.

 

Wow, everything I needed to know and more! Thanks a lot, I feel a lot better about testing it out now.