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91 Subaru Legacy L 4WD Wagon


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I have a 91 Subaru Legacy "L" 4WD Wagon. When I put the fuse in for the AWD/4WD the tranny just slips. Without the fuse in the tranny has no problems. I really need the AWD/4WD. Any ideas on why this is happening?

Thank you.

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I have a 91 Subaru Legacy "L" 4WD Wagon. When I put the fuse in for the AWD/4WD the tranny just slips. Without the fuse in the tranny has no problems. I really need the AWD/4WD. Any ideas on why this is happening? Thank you.

 

i don't think you understand about the FWD fuse. installing the fuse puts the car in front wheel drive, at least it does for all the us legos i've seen. fuse out equals All Wheel Drive.

 

if the car drives with the fuse out but not with the fuse in, i would look for a busted axle or differential in the front. it could be a trans problem, maybe, but i doubt it.

 

read this for more info on AWD and FWD fuse,

 

http://www.ultimatesubaru.org/forum/showthread.php?t=119208&highlight=torque+bind

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Normally I would agree 100%, but I have no fuse in and I have only front wheel drive. When I put the fuse in, the car may or may not move some, then it seems like the tranny is just slipping and the car don't move at all. Take fuse out and front wheel drive works great. ???????????

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Normally I would agree 100%, but I have no fuse in and I have only front wheel drive. When I put the fuse in, the car may or may not move some, then it seems like the tranny is just slipping and the car don't move at all. Take fuse out and front wheel drive works great. ???????????

 

i don't see how. but who knows??

 

try this, there are 3 connectors on the rear of the engine passenger side near the fire wall. the largest one, 16 pins, goes to the trans. unplug it and go for a test drive. you should have:

 

torque bind when turning tight slow circles and only 3rd gear. this is limp mode so you can drive home if the trans computer dies. try it and report back.

 

if you have torque bind, then you have 4WD.

 

how do you know you have only FWD with the fuse out ?

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I will try that and let you know.

I live in NW Wisconsin. Lots of snow and ice. The only two tires that spin are the front two. Been stuck in the snow (yes I have been stuck with a Subaru, hard to believe ). I have had several Subaru's, don't get stuck much when they work.

Thank you again for the help. Will get back to you.

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the TCU, trans control unit, manages the AWD transfer clutch duty c solenoid. this determines how much power is sent to the rear wheels. if you disconnect the computer or or it dies then the trans goes into limp mode. part of this is ''locked'' 4WD which gives you torque bind. the other part is 3rd gear only.

 

if you have torque bind with the 16 pin connector disconnected then the mechanics of the AWD system are working.

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so doing this will not hurt the car at all? I make a living with this car and can not afford to loose it. Sorry if I sound really dumb, Subaru's are a little different than a lot of other vehicles.

 

unplug it, test drive thew car for 5 minutes and then plug it back in. be sure to drive in tight circles on dry pavement. no harm no foul. you should feel binding shuttering jumping and the like.

 

this test will show if the AWD transfer clutch is engaging.

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  • 4 weeks later...

Sorry it took me so long to get this done. We finally got a week in the 35-45 degree range, so it melted some snow and ice off the parking lots. (With 14 pin plug) PLUGGED IN and fuse out- I get FWD ONLY. Plugged in and fuse in- FWD ONLY. (With 14 pin plug) UNPLUGGED and fuse out- I get AWD (on ice I can see the back tire spinning). Fuse in- FWD light is on, but still feels like it's jumping/binding.

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(With 14 pin plug) PLUGGED IN and fuse out- I get FWD ONLY.

 

 

Plugged in and fuse in- FWD ONLY.

 

 

 

(With 14 pin plug) UNPLUGGED and fuse out- I get AWD (on ice I can see the back tire spinning).

 

 

Fuse in- FWD light is on, but still feels like it's jumping/binding.

well first, it is impossible to have torque bind and FWD only, at the same time. unless you actually have a rear diff problem or dragging brakes or bad drive shaft or ..... something. i think a rear diff problem would make noise.

 

the statement in red above means that the mechanical parts are all in place and working. you have 4wd locked when you unplug the trans wiring harness.

 

so now the question, is the TCU working properly? the pages below (thanks eulogious) show the pin out on the TCU and how to test each pin for proper function. give it a read and test the pins for the duty c, FWD fuse and any other related stuff. hopefully you will find the problem.

 

EDIT: if one of your speed sensors is bad that could cause FWD only, but if the front one was bad the speedo wouldn't work. if the connection between the speedo and the computer is bad that could be a cause. if the computer, TCU, does not ''see'' both sensors, it will default to FWD.

 

my personal opinion is that your AWD is working properly, but i'm not driving the car and can not feel what it is doing. another thing you may try if you haven't already. drive it on the hiway with the fuse in and FWD lit. you should be able to ''feel'' the difference in how it drives. (dry pavement.)

 

have you tried spinning the rear tires on ice with the fuse out and the gear selector in 1? i'm sure you must have but don't remember all of this thread and i thought i'd ask.

 

 

 

EJ_TCU_I-O_page1_v2.JPG

 

EJ_TCU_I-O_page2.jpg

 

 

http://www.ultimatesubaru.org/forum/showpost.php?p=996223&postcount=8

Edited by johnceggleston
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Sorry, I did not realize that the speedometer would have anything to do with this. My speedometer does not work, also the tach does not work 95% of the time.

 

ok, we have a winner, maybe.

 

the most common cause of the speedo not working in the 90 - 94 is a bad/ busted speedo cable. this should also cause a CEL, check engine light. (at least it would in an OBD2 car.

 

time to visit a salvage yard.? for a used cable.

 

i don't remember the workings of the tach. fix the speedo first.

Edited by johnceggleston
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