Transfer case switch sync to 4WD

[Thomcat]

Seems I've been driving for about a week with the transfer case switch in the 4WD position. Hasn't felt it was in 4WD and no wheel hopping or scrubbing on the front axle in a tight turn. Didn't think to check the DIC for confirmation when I noticed it while driving but switched to AWD while moving and DIC confirmed switch to AWD and felt transfer case engagement.....likewise down to 2WD and DIC confirmed and transfer case disengagement. Switch function now appears to be working in sync with the transfer case, and there is no apparent evidence of damage.

 

Apparently a few days ago while hoisting my fat a$$ into the vehicle I accidentally nudged the switch from 2WD to 4WD before starting the vehicle. Once started, no message and it felt like it was still in 2WD for the next few days until I noticed the mistaken switch position.

 

Worried I may have done damage driving with the switch in 4WD on dry pavement, I duplicated the error and used the graphic in the DIC to determine wheel/axle engagement. With vehicle parked in 2WD, I turned the switch to 4WD and then started the engine - no message in DIC - no feel of transfer case engagement and DIC graphic confirmed 2WD with rear axle only. Turned off engine switch back to 2WD and restarted - no change in the DIC - no engagement of transfer case - and vehicle remained in 2WD. Then switched to AWD and then 4WD and then back to AWD and 2WD with normal sync of the transfer case and switch and feel of the wheel engagements/disengagements and front axle engagement confirmations of AWD and 4WD in the DIC..

 

My only takeaway is that the transfer case will only sync to the switch position if the ignition is on when the switch change was initiated.....it will not correspond to any switch position made after the vehicle was turned off and the transfer case will remain in the last position it was in when the vehicle was turned off. Thus no action or damage will occur by accidentally changing the switch position before the engine is started and will resync the next time it is switched with the engine on.

 

Make sense????

 

Just tried it again and noticed if the switch and transfer case are out of sync at startup the switch position indicator light is not lit, once resynced it again lights up.

['17 Sierra]

Interesting. That's probably a system protection that was built in for that reason.

[Spurshot]

What would make sense is GM putting a simple lockout button on the switch to prevent inadvertent turning of the switch.

[Nanotech Environmental]

If the transfer case went into 4wd, you would become very, very aware of it, both from the extra driveline noise and when you turned the first corner.

[Sean Neilan]

Im pretty sure I put in 4hi once before starting and it didn't switch and I had to cycle the switch back to 2wd and then back to 4hi. I noticed it hadn't switched because the little orange light on the knob wasn't lit, and when I switched back to 2wd it lit and stayed lit when I put back into 4hi.