[Larry Vollintin]

I got stuck recently in the Sierras on a dirt road when I backed over a large angular piece of granite that dropped the right rear wheel into a hole. All the other wheels were firmly on the ground and the chassis did not high center. I thought the AWD in the 5-speed would pull me out with no problem. But all it did was spin the right rear wheel and burn up the clutch. I managed to get out by slipping the jack under the chassis in front of the right rear wheel and jacking up the car enough to put some rocks and large branches under the wheel and the floor matte over the rocks/branches and up the rock, and I finally got out. But I was very disappointed in the car. So, what gives? Thanks. LRV

 

[Larry Vollintin]

I'm the original poster. Every assumption that Plain OM makes is correct. See photo attached (I hope) But checking my original purchase material indicates that the car has "full-time AWD" and a "limited slip rear differential." So, would that explain why no movement with the right rear wheel hanging over the rock? If so, please help a mechanical peasant understand. Also, the left rear wheel was firmly on the ground, but did not move. And, from some Sub website demos and comparisons of variations on AWD, (see Subaru Symmetrical All-Wheel Drive | Subaru AWD, and

), it would appear that in my situation, the front wheels (and the other rear wheel) should have pulled me out. So, could center diff or viscous coupling you mention be inoperative? How does one check that? A Sub mechanic recently told me "off the record" that a solution to my predicament would have been to open the fuse box under the hood and to put a fuse into the vacant slot marked "FWD" thereby disabling the AWD and turning the car into just FWD. Then, with no power going to the rear wheels, the front wheels should have been able to pull me out. What do you think of that? I don't really want to repeat the experiment and try the fuse thing, but is this mechanic full of it, or legit? Thanks. LRV

 

[Larry Vollintin]

OK, so a few more facts. No part of the chassis was resting on the ground. The right rear wheel was not hanging freely, but certainly without sufficient weight and contact to get traction. The vertical face of the rock showed I left quite a bit of rubber trying to get out. The front wheels were not on loose gravel and did not spin when trying to engage (and burning up) the clutch. I couldn't rock the car as the rear bumper was pushed up against (but not caught on) even larger rocks in the back. I've attached another photo showing how I got out after sliding the jack under the frame and lifting the entire car enough to push some rocks and large branches under the real right wheel and putting an old blanket over the stuff and the rock. With that help, the car pulled right out with little problem.

So, my question is exactly how does the center differential work on my car and how much torque is shifted to the front wheels or to the LR wheel in such a situation? I didn't get any sense that the front wheels were pulling at all.

As to the FWD fuse "solution", I'll go back to the mechanic about the fuse working only for a 4 speed auto. If I'd had an automatic would it have pulled out on its own? Why? Thanks for the comments. LRV

 

[Larry Vollintin]

OM: Thanks for the further response and sorry for the delay. When trying to get the car out, yes, I released the clutch peddle as far as I felt I dared with the engine revving. The car would lurch ahead just a tiny bit each time, but no front wheels spun. With the clutch burning, I felt certain that fully releasing the clutch would have just stalled the car. Yes, I understand that a lot of torque going somewhere would be needed to pull and lift the RR wheel out of the hole. So, then, would the "fuse solution" have worked? By putting in a fuse into the "FWD" fuse slot, would that have disengaged the center VC (or whatever it's called) so that the engine power would have gone only to the front wheels? If so, then that should have pulled me out since the chassis was not stuck and the LR wheel was firmly on the ground, correct? Someone else has suggested that with a MT, that the gearing can't get low enough to work in that situation and that an AT has lower gearing. Would that have made a difference? Also, exactly how does the center VC send power to the wheels with more traction, when the system is working properly? Thanks. LRV