Question on front driveshaft.. should it be turning?

[craig72]

Hey all,
I posted a similar question in the 3rd Gen forum, but figured this might be a better spot.

For a 2016 Platinum with Torque on Demand 4WD (2H, 4A, 4H, 4L options), should the front driveshaft and drive axles be turning while in 2WD? Lets assume the IWEs are disengaged as expected.
Thanks!

 

[GlennSullivan]

They should not be turning. They will turn when the vehicle is rolled with the engine off or jacked up / on a lift when the wheel is rotated as there is no vacuum, which is what disengages the front hubs. When the vehicle is running and there is vacuum to the front hubs the wheels should turn without the front driveshaft and axles turning.

 

[craig72]

That was my suspicion, but thanks for the clarification.
I'm trying to find the source of some drive train harshness we started feeling while in 2WD. Not the typical IWE chatter of them losing vacuum, just a feel in the seat and steering wheel. Feels/sounds like it's in 4WD, which apparently is the front driveshaft and axles turning.

- I've checked the IWEs on both axles and they retract when I start the truck or manually pull vacuum.
- I removed the output hose which applies vacuum to the IWEs from the solenoid and checked it. I applied 25" of vacuum and it held for 5 minutes so no leaks
- During test drive, I can hear the TC motor switch into and out of 4LO so I assume (maybe incorrectly) the TC motor is switching back to 2WD
- Both front hubs were just replaced, sound is still there
- I can observe the IWEs engage and disengage while changing modes (2WD to 4WD) (front of the truck was in the air)

So now I have to figure out why that front drive assembly is moving.
Any one have thoughts? Could it be the TC motor even if its working to get into 4HI/LO?. I suppose I could yank it and watch it move as I change modes.

 

[mr_dave]

If you're sure the IWEs are working and functioning properly, then it has to be the transfer case.

 

[craig72]

Has anyone experienced the TC motor fail where it won't go back into 2WD, but the 4WD modes seem to work as expected?