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I know that a scored MPT Hub can cause binding in the AWD transfer clutches.

BUT, can it also cause the AWD not to function at all?

I have nothing going to the rear. Duty solenoid C is not throwing a code(and it hums when energized), and the MPT Hub is not broken, but it is heavily scored. I thought this would be a bad transfer clutch pack, but the PO of the tranny said that it was replaced b/c of binding in tight corners. So I am thinking that there should be some meat on the clutches if it can bind. Any thoughts.

This is my 4.44 swap from 1996 Outback into 1991 Legacy. Rear is 4.44 as well.

How have you verified the lack of power to the rear?

Could it be possible for the Duty C to be physically stuck in the open position without actually being broken? It seems to me that in that case it would not throw a code and yet still not be working.

Alphius wrote:How have you verified the lack of power to the rear?

By the front tires spinning incessantly. Nothing beyond that.

Could it be possible for the Duty C to be physically stuck in the open position without actually being broken? It seems to me that in that case it would not throw a code and yet still not be working.

That's another good question that I was going to ask.

Hi,

This is my 4.44 swap from 1996 Outback into 1991 Legacy. Rear is 4.44 as well.

The '96 was plug-n-play? Did you use the '91 or '96 TCU?

Does the FWD fuse work?

I've read mixed reviews on using the OBD2 trans in OBD1 cars

I also read that you've done MANY trans swaps, so you should know!

Td

Here's a thing I thought of:

With the Duty C solenoid completely unplugged/disconnected you should get full transfer plate engagement and 50/50 torque split with bad torque bind.

So unplug the Duty C or disconnect the Duty C wire from the TCU plug and see if you get fully locked AWD. If you do, then there is an electrical problem. If it's still FWD at that point you need to start tearing the transfer pack and Duty C out of the transmission and testing/replacing them as in that case it would have to be a mechanical problem. I would lean towards a bad Duty C since you said the clutch pack is fine. I don't believe a scored MPT clutch hub would cause your problem, but I could be wrong.

wtdash wrote:Hi,

This is my 4.44 swap from 1996 Outback into 1991 Legacy. Rear is 4.44 as well.

The '96 was plug-n-play? Did you use the '91 or '96 TCU?

Does the FWD fuse work?

I've read mixed reviews on using the OBD2 trans in OBD1 cars

I also read that you've done MANY trans swaps, so you should know!

Td

It was plug-n-play. I've only seen the same two plugs on phase 1 4eats. I used the same year tranny on my 92 SVX to get the 4.44s and many others in the svx.net site had done this as well with no issues that I saw. I've done lots of tranny swaps but have had few AWD issues among them. I guess I've been lucky.

The fuse gives me the FWD light and no change in driving.

I think I'm(as is Alphius) leaning toward DS-C

I appreciate all the input. Its great to get other perspectives.

Alphius wrote:Here's a thing I thought of:

With the Duty C solenoid completely unplugged/disconnected you should get full transfer plate engagement and 50/50 torque split with bad torque bind.

So unplug the Duty C or disconnect the Duty C wire from the TCU plug and see if you get fully locked AWD. If you do, then there is an electrical problem. If it's still FWD at that point you need to start tearing the transfer pack and Duty C out of the transmission and testing/replacing them as in that case it would have to be a mechanical problem. I would lean towards a bad Duty C since you said the clutch pack is fine. I don't believe a scored MPT clutch hub would cause your problem, but I could be wrong.

When I swapped the tranny in I took the C out of the bad tranny that I replaced b/c it didn't throw a code, I assumed it was good. But the bad tranny didn't have AWD or 2nd or 4th gear. I assumed the clutch pack was bad b/c no power light. I guess that's what I get for assuming.

I found a write-up on testing C so I'll go that route as soon as I get an ohmeter. Thanks for the help.

Anyone know the cheapest place to get a new duty solenoid?

I have a couple of extras laying around, but I don't think I want to waste anymore time with used parts.

Try putting the gear selector in 1. That is supposed to put the torque split close to 50/50.

If you have a better/less grooved hub I'd use that as well.

Here's dealer part number for the Duty C.
31942AA070 - DUTY C
It's just over $100 on 1stsubaruparts.com.

If it was me I'd try to use one of your used ones before dropping that much. It would at least isolate the problem a little better without just throwing money at the situation as long as you have a used one that you can reasonably expect to be working correctly.

Alphius wrote:If you have a better/less grooved hub I'd use that as well.

Here's dealer part number for the Duty C.
31942AA070 - DUTY C
It's just over $100 on 1stsubaruparts.com.

If it was me I'd try to use one of your used ones before dropping that much. It would at least isolate the problem a little better without just throwing money at the situation as long as you have a used one that you can reasonably expect to be working correctly.

Thanks for the info. Money isn't so good at the moment so I will have to try the used ones first. Probably Thursday. I got sidetracked this weekend tinting the windows and a little trim painting.

Well, I did what Josh suggested and got grip in the rear so I guess it's gotta be C then. But my stupid alternator went out and took the battery with it so that will be another minor setback.

Very odd. So you don't get engagement in D but in 1 you do? Seems to me that if that's the case the Duty C is fine. Unless that result is not repeatable.

Alphius wrote:Very odd. So you don't get engagement in D but in 1 you do? Seems to me that if that's the case the Duty C is fine. Unless that result is not repeatable.

Correct. I don't get engagement in D but I do in 1.

But I thought puttting it in 1 bypassed the function of the duty solenoid.

Putting it in 1 just changes the TCU programming to be more aggressive.

I suggested this before, but it is the best way to ensure that the car is locked at 50/50. Remove the wire from the TCU connector that goes to the Duty C. You should get a TCU trouble code when you drive the car, but that will remove the signal to the Duty C solenoid which will lock the rear output to the front output, giving you 100% full AWD.

Check this for identifying the wire. I don't know if it's a different wire on the first gen cars but I can take a look at my FSM tonight if you want.
http://www.rs25.com/forums/f8/t99075-4e ... ost1583994

If you remove that wire from the connector temporarily and you do not have AWD then there is a mechanical problem with the Duty C. If you remove that wire and you do get AWD then it would seem the Duty C is not stuck and you have a TCU or wiring issue.

EDIT:
Maybe you're just not waiting long enough for the TCU to engage AWD in D? It is possible to spin a front tire for a revolution or two before engaging the AWD if you just floor it in D. My girlfriend's Outback does this sometimes in the rain if you're too aggressive from a stop.

My preferred test:
1. Find gravel road
2. Floor it in D and see what happens. Don't let off for at least a few seconds. (Spin fronts, then all 4)
3. Insert FWD fuse, repeat test. Observe differences. (Spin fronts. A lot.)
4. (optional) Remove Duty C wire from TCU harness. Repeat test. Observe differences. (All 4 from the get go)

Maybe you will find it is working fine? Working in 1 but not as well in D leads me to this conclusion.
Of course, if it still fails in D during this test and just spins the fronts exactly the same as in FWD I would suspect a TCU issue since at this point we would have verified the complete operation of the Duty C solenoid.

EDIT 2:
Hmm, maybe the Duty C is still bad. I just thought of a failure mode where it doesn't work progressively anymore but doesn't throw a code, maybe due to being partially stuck. Here's my thought process with examples.
So the TCU commands a percentage of lock with a PWM signal between let's say 0%-100%. So what if the solenoid doesn't respond at lower duty cycles? For instance, solenoid is slightly sticky and won't activate at PWM duty cycles below 75%. Then, at any point of commanded duty cycle below 75% the DS-C actually applies 0%, but over 75% commanded it suddenly has a long enough pulsewidth that it applies? It would look like this:

Command-0%--25%--50%--75%--100%
Actual -----0%---0%---0%---75%--100%



In Summation (sorry long post):
Perform more testing
Depending on result of accurate testing, two options:
It's working correctly
-or-
Replace Duty C

Thanks for all the continued help.

Its definately spinning freely up front and it doesn't get better with duration.

I found the troubleshooting flow chart and tested the resistance from #4 (blue) to #11 (black/white) on the square plug and it is open.

I should reiterate that this transmission was said to have torque bind by the PO and when I installed it, it flashed a C light. I replaced the C before even driving it with the one from my old tranny(probably my downfall). The old tranny had no Power light and no AWD. I assumed <DTOH!> that C was good and the prob was mechanical on that one. I'll be swapping another C in tommorrow.

Solved my alternator problem though. I was heading out to the JY to get an alternator to replace mine, which had an output of 10.7 V. But I thought I would add a ground from the alternator frame to the neg battery post first. Output jumped up to 13.4 V and saved me a trip to the JY in my gas-guzzling van. Wild

Also should note that the 4.44 FD is a blast to drive. Should be a good match for my torquey frankenmotor.

That's a very odd problem then. The most likely thing I can think of is still the Duty C, so I think you're on the right track.
Make sure you check back in here if it's fixed after you replace it, I'm very interested in the resolution!
Glad to help. I know sometimes having more than one brain working on something can help give some new insight.

If I didn't drive highway so much in my '94 I'd love to have a 4.44 5 speed. I hear it's pretty wild!

Alphius wrote:That's a very odd problem then. The most likely thing I can think of is still the Duty C, so I think you're on the right track.
Make sure you check back in here if it's fixed after you replace it, I'm very interested in the resolution!
Glad to help. I know sometimes having more than one brain working on something can help give some new insight.

If I didn't drive highway so much in my '94 I'd love to have a 4.44 5 speed. I hear it's pretty wild!

I definately will share the results here. I don't know how many times I find a thread with pertinent info on a search and then only to find no details of the resolution.

The 4.44 is really fun right off the line, but loses steam once you get up around 60-70. I did it on my SVX a few years back and the difference was incredible. The stock FD was 3.545 so it was very dramatic. The car launched like it had lost 1000 lbs. It was great fun off the line, but it kind of ruined the high speed capabilities of the SVX. I miss that 3rd gear that would take you from 60 to 120 or so.

Well, I got the duty solenoid C and MPT hub replaced and got everything back together, put ATF in it and then found the thin bearing washer that goes between the hub and clutchpack laying on the ground. DTOH! It took me an hour and 40 mins start to finish.

So I went back and redid basically everything to put the bearing back and that took me an hour flat. Of course, if i took one more minute the first time, I wouldn't have had to do it twice. But an hour is pretty quick.

I haven't had a chance to test it out yet, but I know there is no power light. I also tested the C that I replaced and it tested 13 ohms which is in range. So that makes more sense because if it was open it would have thrown a light. I think I just tested it wrong in the car.

So if this doesn't get me my AWD back, then I guess I'll swap in another TCU. Fortunately, I have a couple extras.

Today was a good day.

It must have been duty Solenoid C because it is back in AWD now. It rained all evening and I couldn't break the front tires once, even a little bit. I actually briefly spun the inside rear tire taking off on a turn in gravel so everything is looking good now. A big thanks to Alphius for keeping me thinking.

So to celebrate, I had to go and buy a 96 L Sedan AWD. Paid $1000 but seems to be worth more than that. On top of that, it came with a spare 5 spd tranny, brand new full clutch set in box, new windshield, and a huge box full of extra parts. Most of the interior has been converted to Outback leather. The guy had a 96 Outback at his work that he stripped at will. And also nice rims/tires and nice sound as well. Only thing is that the front end was rebuilt and looks like an Outback with white over grey while the rest of the car is dark blue. But no dings on the body so a full paint job will be in order.

Yes, today was a good day.

Alphius wrote:How have you verified the lack of power to the rear?

Could it be possible for the Duty C to be physically stuck in the open position without actually being broken? It seems to me that in that case it would not throw a code and yet still not be working.

You nailed it in your first response. ECU read 13 ohms and thought it was good so it didn't throw a light. But it didn't go.

That is awesome! I'm glad all is fixed and the '96 sounds like it was a good deal. Glad I could help.

Yes, glad you got it fixed and it's back to AWD!