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-   -   AWD not working (http://www.subaruoutback.org/forums/66-problems-maintenance/16493-awd-not-working.html)

merigold2005 12-20-2008 09:27 PM

AWD not working
 
Hi,I have a 2000 Subaru Outback Wagon and we just had our first real snow storm this year.I hadn't paid much attention before but today I noticed that if I take off fast in the snow my front tires spin alot and not the rear.Is that normal to happen.I thought AWD was if tires were spinning,they all would be spinning.Also,shouldn't traction control keep the tires from spinning?I don't know anything about this stuff so any help from you guys would be greatly appreciated.I don't hear any strange noises or anything.Thanks in advance

bsevic 12-20-2008 10:24 PM

How long have you owned the car? Do you have or did someone else install the fuse that disables the AWD? It's located on the passager side near the firewall in my 98.

nipper 12-20-2008 11:45 PM

any flashing lights on the dash on startup?

nipper

merigold2005 12-21-2008 09:46 AM

AWD not working
 
The AWD was working before and I didn't have a fuse installed.There aren't any flashing lights when I turn the ignition on.When I turn the ignition on,should there be a light that says AWD?If so I haven't noticed one that lights up at all.Am I right in thinking if the front tires spin the rear should be spinning also?Thanks for all the replies.

plain OM 12-21-2008 11:06 AM

Re: AWD not working
 
"The AWD was working before and I didn't have a fuse installed.There aren't any flashing lights when I turn the ignition on."

When the ignition switch is turned to ON (not Start), there should be an "AWD" (or "FWD") light and an "AT Oil Temp" light on, at least briefly. (They should go out when the engine is started.) A flashing light indicates a problem detected by the on-board diagnosis system.

"Am I right in thinking if the front tires spin the rear should be spinning also?"

If you have an automatic transmission, if both the front wheels are spinning while both backs are not turning or are turning much slower, then the AWD is not working properly. But it is possible for both (or one) front and at the same time both (or one) rear to be spinning even with a properly functioning AWD system. This is because the AWD system only ensures that the front and rear drive shafts are turning at the same speed. It does not control the differentials at the front and rear axles. The differentials can allow one of the two wheels (right or left) to turn faster than the other.

merigold2005 12-21-2008 11:21 AM

Re: Re: AWD not working
 
Quote:

Originally posted by plain OM
"The AWD was working before and I didn't have a fuse installed.There aren't any flashing lights when I turn the ignition on."

When the ignition switch is turned to ON (not Start), there should be an "AWD" (or "FWD") light and an "AT Oil Temp" light on, at least briefly. (They should go out when the engine is started.) A flashing light indicates a problem detected by the on-board diagnosis system.

"Am I right in thinking if the front tires spin the rear should be spinning also?"

If you have an automatic transmission, if both the front wheels are spinning while both backs are not turning or are turning much slower, then the AWD is not working properly. But it is possible for both (or one) front and at the same time both (or one) rear to be spinning even with a properly functioning AWD system. This is because the AWD system only ensures that the front and rear drive shafts are turning at the same speed. It does not control the differentials at the front and rear axles. The differentials can allow one of the two wheels (right or left) to turn faster than the other.



I forgot to mention that my car is a manual transmition if that makes any difference.I just checked my car and when I turn the ignition on there is no light that says AWD or FWD at all.Not even for a second.Thanks again for the replies.

merigold2005 12-21-2008 11:35 AM

AWD not working
 
Hi and thanks for the replies.I stupidly forgot to mention my car is a manual transmition if that makes a difference.I just went out and checked my lights and there is no light at all that says AWD or FWD when I turn the ignition on or start the car.

plain OM 12-21-2008 11:57 AM

That does make a difference. The manual transmission uses a mechanical AWD system -- no electronics = no instrument panel AWD or AT Temp lights, and no AWD/FWD fuse.

There is a limited slip differential in the transmission that splits power between the front and rear drive shafts. Normally this differential allows the front and rear driveshafts to turn at different speeds, as is necessary when turning a corner. But when the difference in speeds is significant (e.g. front wheels spinning), a viscose fluid inside the differential heats up (due to the difference in drive shaft speeds) and this effectively locks the driveshafts.

If the difference in driveshaft speeds is short-lived, or if the speed difference isn't great, then the fluid will not heat up enough to fully lock the differential.

If it worked before and there is a noticeable difference now in much the same situations, then it's possible the limited slip action of the center differential might not be functioning properly.

merigold2005 12-21-2008 12:38 PM

AWD not working
 
I think I understand.I did notice all summer that when I parked my car there was a fluid leaking under it.Not alot but a few drops where I parked it every day.I always thought it was either brake fluid or clutch fluid.It was a clear fluid.Think it may have been fluid from my center diff and now it is dry?Is there any way to check the fluid level in the diff?Am I destroying my car driving it like this if that is the case?Thanks so much for your help.

plain OM 12-21-2008 03:47 PM

The center differential (which is essentially a set of gears) is part of the manual transmission and is lubricated, along with the rest of the transmission, by the transmission's gear oil. However, the limited slip mechanism itself is a separate sealed assembly inside the transmission that works in conjunction with the differential gear system. It is this assembly that contains the special viscose fluid. The transmission oil level can be checked using the transmission dipstick, but this will not tell you if the viscose fluid is intact.

Think of a sealed metal can filled with fluid inside a larger bottle that is filled with fluid. (The can is the limited slip assembly The bottle is the overall transmission housing.) You can check the level of the fluid in the outer bottle by taking the cap off and looking inside, but there's no easy way to check the level of the fluid in the sealed can. If the can were to develop a leak, its fluid and that of the jar might mix, but the overall level of fluid in the bottle would not change. Also, if both fluids are more or less the same color, there would be no way to tell if the can is leaking by looking at the color of the fluid in the bottle.

If the seals on the limited slip mechanism leak, the heat sensitive viscose fluid that is inside and the surrounding transmission oil will mix. As a result, the viscose fluid inside the mechanism will be diluted and would no longer function properly to lock the front and rear drive shafts when a wheel is slipping. This doesn't happen often, but it is possible.

If the viscose fluid mixes with the transmission oil, this will not likely damage the rest of the transmission long as the overall oil level is okay.

The transmission has a dipstick on the right (passenger side) of the transmission, behind the engine. The dipstick is quite low down at the back of the engine compartment. It can be difficult to find the first time, but once identified, it provides a way to regularly ensure that the transmission oil level is correct.

The clutch fluid and brake fluid can be checked more easily -- each has a clear plastic reservoir in the engine compartment. However, if you think either is leaking, have it checked right away. Loss of these fluids can lead to loss of control of the car.

The Owners Manual has instructions about checking the various fluids. If you're not familiar with checking the fluid levels in a car, and don't have the Owners Manual, have someone who is familiar with Subarus show you how.


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