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duty solenoid


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3 replies to this topic

#1 bennon

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Posted 05 December 2003 - 02:17 AM

Hi. I have a subaru legacy station wagon, L, 1996 with 115k miles. the light that says AT OIL TEMP flashes 16 times every time I start the car and than it turns off (it does not turned on while the car is on). I understand it indicates some type of a problem. in the dealership thay told me that the problem is with the duty solenoid and that the car will just stop working in a year (they told me that a year ago). they also told me that they don't deal with such problems because it's very expensive to take out the transmission and because you always find more problems when doing so. does anyone have a suggestion regarding how to take care of such problem. I appreciate your time. oh! I forgot to mention that so far the car is driving perfectly and I haven't had any major problems.
Ben Shachar

#2 alias20035

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Posted 05 December 2003 - 03:13 AM

Originally posted by bennon
Hi. I have a subaru legacy station wagon, L, 1996 with 115k miles. the light that says AT OIL TEMP flashes 16 times every time I start the car and than it turns off (it does not turned on while the car is on). I understand it indicates some type of a problem. in the dealership thay told me that the problem is with the duty solenoid and that the car will just stop working in a year (they told me that a year ago). they also told me that they don't deal with such problems because it's very expensive to take out the transmission and because you always find more problems when doing so. does anyone have a suggestion regarding how to take care of such problem. I appreciate your time. oh! I forgot to mention that so far the car is driving perfectly and I haven't had any major problems.
Ben Shachar



The duty solenoid is used to control the amount of power sent to the rear axle. The duty solenoid is located in the tailshaft assembly of the 4EAT transmission along with the torque transfer clutch pack. Replacement of the duty solenoid can be done with the transmission in place (although it is sometimes easier to drop the transmission). It is not a hard repair, and the damage is all limited to the tailshaft, I am not sure why the dealer is hesitant.

Are you having any problems with "torque bind"?

Torque bind occurs when the clutch pack or duty solenoid is defective. Torque bind is usually observed as a rumble or vibration that occurs in moderate and sharp turns. You may also note that the car feels like the brakes applied during a turn, but you did not apply them.

What happens is the transfer clutch sticks and locks the front and rear axle together, but when you turn the rear axle always has to turn slower than the front. This builds up torque bind on the drivetrain that can not be released, and is felt as rumbling, a vibration and/or braking.

Take a shift on the fly 4x4 and place it in 4 hi or 4 lo, then try to do donuts in a parking lot. What you will experience is torque bind, same as the Subaru.

Your transmission is the early generation 4EAT which has a poorly designed tailshaft assembly which has a steel part rubbing on the aluminum case of the tailshaft. Since aluminum wears faster than steel the result is hydraulic pressure problems and torque bind. Torque bind due to this wear to the aluminum case almost always occurs betwen 80 and 140 K miles, so your 115K falls in the middle of this.

What you need is the revised tailshaft assembly which has a steel sleave to protect the aluminum tailshaft case and a new duty solenoid. Cost $750-$1,000 for parts and labour. This problems affects nearly 100% of all 4EAT's prior to 1998 (when Subaru changed the design), why would the dealer not know about this? Find another dealer or independant Subaru repair shop.

BTW: your 4EAT is perfectly fine and will last pretty much forever, it is just the AWD mechanism that has gone wrong.

It is generally not a good idea to drive around with a failing duty solenoid, especially if you are experiencing torque bind. Torque bind places a lot of wear and tear on the rest of the drivetrain and you may end up destroying your driveshaft, rear axles, and rear differential. In your case you simply may not have any power to the rear axle, if the TCU detects a fault with the duty solenoid it will try to hold the car in FWD (which is not good).

Do you have any snow and ice near Tucson to test the AWD? If got about 12" of snow with about 15" or more this weekend to test mine here in Canada..... Actually I just checked the Tucson forecast and it will hover around 25C for the weekend so I guess snow is out...

You might also want to inspect the electrical harnesses on the 4EAT, sometimes these are damaged or loose, and if so the TCU could report a duty solenoid failure. I have seen loose wiring harnesses on two occasions, both times after a dealer inspected the transmission.

#3 bennon

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Posted 06 December 2003 - 04:16 PM

thank you very much for the information. I'm almost sure I have that torque bind so it is probably not an electrical thing. searching similar messages in this forum, other people suggested putting in a fuse that cancel the AWD (I assume as a temporary solution that prevents further damage). is that a good option? also, I have been driving like this for around 9 month (with no problems at all) and around 20k miles. have I caused a lot of damage? maybe now I have to replace other parts such as the differential which are more expensive. anyway, it seems like I need a new solenoid and a new tailshaft assembly. do you recommend coming back to the dealership (who gave me incomplete information in the first place, which may have caused some damage) or searching for other places. does anyone know a good place around tucson for those kinds of things, maybe a good transmission place? maybe searching for these parts in a junk yard (I'm a broke grad student)? thnak you very much.
Ben

#4 dashton

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Posted 06 December 2003 - 10:47 PM

Ben,

Please do a search for the following post:

"starting to hate this car(tranny) Help!!" by Patcal. I think it's on about page 4 of the forum. He had a similar problem to yours and it turned out to be just a bad TCU. He's done some diagnostic work to determine if it was the solenoid or the TCU and it worked out pretty good.

By the way - a bad clutch pack or tailshaft housing will NOT cause torque bind, it will only cause the tranny to shudder and slip when the computer locks it up in 4WD. The torque bind is caused by the solenoid opening up and porting fluid to the clutch when it's not supposed to. This can be caused by a bad solenoid, bad wiring, or bad TCU. And if you have to replace the solenoid it's very easy to do yourself if you have a little mechanical background. Dave




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