Subaru AWD

subaru
impreza

#1

I purchased a 1997 Subaru Impreza Outback wagon. I notice when backing up and turning the rear wheel on the inside of the turn, binds and even slips on gravel, like the differential isn’t working. I have had the fluids changed in the front & rear differentials although the fluids looked clean. Is this a sign of serious problems? I don’t notice this when going forward.


#2

You may be experiencing something called torque bind. This is an all wheel drive vehicle and there is a center differential inside your transmission. If you have an automatic transmission and you haven’t changed your transmission fluid yet, that’s the first thing I’d try. If it’s a manual, it should be looked at by someone who knows Subaru’s, because replacement might be the only option.

Another thing you can try is turning off the AWD system. This is done by installing one of your spare fuses in the empty slot in the underhood fusebox labeled FWD. This will shut down the AWD system. It will also turn on a warning light on your dashboard to remind you that the AWD system is disabled. If the problem goes away, the center differential might be causing your problem. If it doesn’t go away, your center differential may be locked up and that wouldn’t be good.

You might also want to go to www.subaruoutback.org, they have several forums that might answer your question better than I can.


#3

Most excellent response. tcarlozi, I hope you become a regular member. Also one basic recommendation is to have any used car checked out by an independent shop, I fear calvincool did not do that.


#4

Consider too that Outbacks (Impreza ?) had a mechanical limited slip “rear” differential as well which may be locking prematurely in reverse. Whether that’s normal is up to the dealer, but they do wear over time,. especially if they have been given less than the token service of an open differentials.

I would look at that problem before the center diff. as that’s only responsible for sending power to the rear, not distributing it to either side as the mechanically controlled LSD in the rear is…

On the centers, the manuals have viscous mechanically operated centers, the autos are electronically controlled as tcarlozi said, at least it was in my 96. So your center diff may not respond to fuse removal if it’s a manual.

PS, I just Googled and there appears to be a reference in Subbie support site to a LSD in the rear of the Impreza Outback Sport. It appears, they came so equipped. So that would be on my hit list too.


#5

Thanks for the great responses!


#6

I disabled the AWD as you directed, and the problem disappears. I haven’t had the automatic transmission fluid changed yet, but I plan to. Are there any filters in the transmission that should be changed? The fluid appears clean at this time.


#7

Try a transmission fluid change. It might help.

The problem might be a worn transfer valve and clutch pack, which is located in the rear of the transmission. When you insert the FWD fuse you disengage the clutch pack and disable the rear drive.

When the valve starts to wear it allows the clutch pack to remain engaged when it should be releasing, and the front and rear ends will fight each other and bind. You may notice it on tight turns, too, like turning into a driveway or parking space.

The symptoms you describe are exactly what I noticed on my '96 Lagacy automatic. The valve and clutch pack were replaced and the problem went away.

See the “Shuddering Forester?” post for more info.