Cold weather drivetrain question

[Spooler]

Hey guys,

My car is experiencing something weird under cold weather (below 15F) at startup. With transmission in neutral, the RPM drops drastically (like 500 rpm) when I release the clutch. What concerns me is that the car moves or squats if the hand brake it is engaged. So power is making it to the rear wheels. I have my thoughts on this issue, but I would like to get your comments on the matter before I share them so I don't bias the discussion.

Thank you for your help.

Spooler

 

[brandini]

moving/squatting does not mean rear wheels, it means any wheels. I can do the same in a FWD minivan.

 

[Spooler]

moving/squatting does not mean rear wheels, it means any wheels. I can do the same in a FWD minivan.

I came to that conclusion based on the fact that there is no physical way to engage the front wheels if the tranny is not in gear. And it feels like a rear squat more than a front pull/rear squat.

 

[brandini]

Ok so you need to test for something with the clutch going bad then if you're getting ANY movement with the clutch depressed.

You should be:
-shift to neutral
-press clutch
-start car
-release clutch
And if done in that way there is no possible way to get movement.

If you:
-press clutch
-start car
-shift to neutral
-release clutch
It's possible to get some movement if the clutch does not fully disengage, or if it's re-engaging due to a pressure leak from a bad master/slave/clutch line.

With the handbrake pulled the 6's AWD system will cut power to the rear wheels but a very minute amount will still go back there (from it being a wet clutch to the rear). So if you lift the car, pull the ebrake, and put it in gear the rear wheels will move a bit. The power is always sent to the rear via the driveshaft, but the rear diff houses a fancy computer controlled clutch to engage and release to modulate power.

 

[Spooler]

Car is in neutral before I crank, as described in your first startup procedure. I think something is freezing in the transfer case or rear diff since this only occurs under very cold temperatures. My initial startegy was to replace all fluids to see if it helps. Anybody else with this issue? I'm sure there is a bunch of MS6 in Northern US and Canada which have experienced similar symptoms.

 

[brandini]

That's the thing, unless you are in gear, the driveshaft to the rear will NOT turn.

 

[Spooler]

That's why I am puzzled by this. Anybody else with such issue?

 

[brandini]

I think you're placebo-ing something. Are you parked on a perfectly flat surface? Can you have a friend start the car with the ebrake off and video the car?

 

[Spooler]

I'll do that tomorrow morning, today we are above freezing and the issue is not occurring.