Subaru Forrester All Wheel Drive Spins Only One Wheel?

Last year we bought a 2007 Forrester with all-wheel drive. Last week I tried to drive it up the driveway when it was icy. It didn’t.

While my son, my wife, and I pushed, sanded, shoveled, and salted, I noticed that only the front-right tire was actually spinning. The front-left tire remained stationary when we touched the accelerator. Neither first gear nor overdrive caused it to spin. Why?

It sounds like your AWD system is not working. If the system was in front-wheel drive mode rather than AWD mode, a slippery surface could cause one of the front wheels to spin, just as with a regular FWD vehicle, and you could wind up with little locomotion–as you found out.

Since Subaru’s AWD system is not readily switchable from AWD to FWD, it certainly sounds like you have a mechanical problem. While your powertrain warranty is still in effect, I would suggest that you get this vehicle to the dealership a.s.a.p for diagnosis and repair.

check your owners manual…I think there is a fuse that controls AWD/FWD in a subaru

At least one rear wheel should have been turning. Did you notice both were not or just focused on the front?

Is the center differential a conventional (non-LS) design, or is it limited slip? Just as an axle’s (non-LS) differential can deliver all power to the slipping wheel*, could the center (non-LS) differential deliver all power to the front axle? Just a thought…

  • some ignorant people, upon seeing this, insist that only one wheel is driven (and the other always spins freely) by the axle

There is a fuse that controls this. However, switching from AWD to FWD on a Subaru involves inserting a fuse into a particular fuse holder near the firewall on the passenger side. The Owner’s Manual will show the exact location and this information should be in the section of the manual that deals with tire changing.

I guess that it is worthwhile for the OP to check this point, but unless someone inserted that fuse when running on the temporary spare and then forgot to remove the fuse, that scenario isn’t likely to be the problem–IMHO.

The rear wheels get power through a fluid coupler. The design puts most of the power transfer on the front differential, with is not a limited slip design, being on the front axle. The rear axle, when activated as described above, does not get an equal share of the engine’s power, but maybe 35-40% power transfer share.

It could be that the car is not damaged at all. This is just the reaction you will get when the front axle is on completely tractionless surface, and the power to the rear wheels is not enough to climb a steep driveway. AWD and FWD will improve traction on slippery surfaces, but is not magic on ice. Zero traction is Zero traction, no matter how many axles get power.

It all depends on transmission. My manual transmission has a viscous coupling(mechanical) that splits power 50-50 typically on my WRX. If your really stuck usually both rear wheels will spin but sometimes one. The front one or the other spins. The WRX’s rear has a LSD on the WRX but not on Forester’s except maybe the turbo model.

If this is automatic the power split is more biased towards front but typically a one rear will spin too, this is controlled by an electronic clutch pack in the center differential.

Thanks for all the feedback. I’ll have a mechanic look into it and report on the results.