5EAT in 2wd problem...........

[AWDPete]

My '05 OBXT is giving me grief! I only have 44,000 miles on it and it's all bone stock. I believe I only have front drive as evidenced by the excessive front wheelspin! The tranny also acts like it's slipping - similar to a manual gearbox with a bad clutch when I get up to 50mph or so, the revs pick up when I try to accelerate and it feels like it "catches" when I let off the throttle. I don't have any warning lights on......what the heck is going on!?!?

[CNY_Dave]

have you checked the trans fluid level?

Dave

[AWDPete]

Forgot to mention the trans fluid level is fine.

[plain OM]

Hmm . . . it's a 5EAT, which uses the VTD AWD system -- a planetary differential to which both the front and rear driveshafts are permanently connected. However, being an inherently open differential, it's possible for one output to turn freely (spinning front wheels) while the other is stationary (rear wheels). However, the AWD component uses a multi-plate clutch that locks the differential when the two outputs tend to turn at different speeds, thereby forcing the front and rear driveshafts to turn at the same speed. Putting this together, if the front wheels spin while the rears don't turn (neither wheel is turning), then either the clutch isn't engaging (a control problem) or it is, but it's worn out and is slipping.

Has the transmission fluid ever been topped up or changed? I ask, because the 5-speed requires Subaru type HP fluid, not the more common Dexron III or equivalents. And if it hasn't been changed, perhaps a few drains and refills (see the "Changing automatic transmission fluid is easy" thread in the DIY section) might clear up the symptom. (Only 44k miles, but a fairly long time since new.)

[AWDPete]

The car drives like the clutch is disengaged - it feels like a front wheel drive car. Maybe I will try putting in the "towing" fuse to see if I can cycle it.

The fluid has never been topped or changed and the level is where it is supposed to be.

Any ideas about the 'slipping' at higher speeds?

The weird part is that it just happened literally overnight. I did notice a couple of hard shifts into second gear and it would hold first gear longer then usual but it's been in the single digit temperature wise.

[plain OM]

You could try the fuse, but it's my understanding that the AWD fuse does not work with the 5-speed. (There was a discussion here about this some time ago, and I seem to recall that it was confirmed by Subaru.)

The lack of rear drive and the high speed slipping might indicate a transmission control problem. This usually will trigger a warning light (AT Oil Temp, "Sport" flashing). Might be worthwhile seeing if there are any trouble codes stored for the transmission. ( http://www.subaruoutback.org/forums/...odes-dtcs.html)

[AWDPete]

OK, I'll try reading the diagnostic trouble codes.

Thanks for your help! Much appreciated!

[AWDPete]

OK, read the codes but have no clue as to what it means! I don't have any "P" codes but I have two "C" codes: 106 and 108. The resources listed above only show the P codes, where do I find info on C codes?

[plain OM]

Those codes are for the ABS system. The 106 and 108 (C0106 and C0108) are left rear and left front wheel sensor malfunctions. If the ABS warning light isn't on, then these might be codes set some time back, but for which the original problem has since been resolved. (As long as the ABS warning light itself does work when the key is set to ON but the engine is not started.)

No transmission codes -- it could well be a slipping/not engaging AWD clutch. But the only way to tell for sure is to first check the signals from the transmission control unit to the clutch solenoid, and the hydraulic pressure at the clutch piston. This is usually a dealer job as it requires a device, such as the Subaru Select Monitor, that can read the TCU signals.

It's possible that the main line pressure in the transmission is somewhat low, leading to slippage not only in the AWD clutch but elsewhere (at speed). This can also be diagnosed using the SSM and appropriate pressure gauges.

[Seabass]

Any chance that the transfer clutch disables when there is a wheel speed sensor malfunction? Bad wheel speed sensors could drive the AWD system crazy without a failsafe.