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Old Mon 21st May 2012, 07:48 PM
Liberty Valance Liberty Valance is offline
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4EAT MPT Clutch assembly

Vehicle: 1990 Liberty GX AWD Auto Sedan

I was experiencing torque bind so went straight in for the Duty C solenoid and what I found was very surprising.

Please view the attached photo.
The extension housing on the left is from my car.
The one on the right is from the same model car.

Both are standard TZ102ZG1AA auto transmissions which match the compliance plate on the vehicle but that's where the similarity ends. They have a completely different MTP assembly. I can't even find rear transmission mounts to suit my car as the extension housing is also a different shape on the outside.

Every automatic first generation AWD Liberty I have looked has a MPT clutch and extension housing on the right. My suspicion is that the box on the left is from an imported vehicle maybe bought unknowingly from a wrecker or left over from a front cut?

I have tried to solve this problem myself and have had some of the best Subaru minds look at it. We are all stumped. Does anyone on this forum have a suggestion about what type of transmission I am looking at here or what vehicle it may have originally come from?

Thanks in advance, Scott.
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Old Mon 21st May 2012, 08:19 PM
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Gannon Gannon is offline
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Have you got more photos with the rear transfer units removed. The one on the left has a gear visible, if it makes up a planatery gearset, you have yourself a VTD or Variable Torque Distribution gearbox, or at least rear end. But to my knowledge, these didnt come out till the 2nd generation turbo models
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Old Mon 21st May 2012, 08:51 PM
Liberty Valance Liberty Valance is offline
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It's a shame I didn't take a photo of the rear end of the transmission with the extension housing removed. If I try to describe it I would say there is a clutch basket with three planetary gears visible behind still attached to the output shaft when the housing is taken off. That could be a match to what you are describing.

The only other photo I have is of the extension housing still in the vehicle.

If it is a VDT that could explain why I'm still getting torque to the rear with a full 12V on the duty C solenoid. From my brief reading they seem to be performance oriented with rear wheel torque bias.
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Last edited by Liberty Valance; Mon 21st May 2012 at 09:03 PM. Reason: New thought
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Old Tue 22nd May 2012, 06:36 AM
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This is a vtd diff




In open mode, it operates as a normal, open differential with a slightly biased torque split of 40 front /60 rear. When locked it gives a 50/50 split or the ECU can vary it anywhere in between.
But I cant remember if it is open or locked when the ECU is giving 100% +12v on duty C. I have a feeling its opposite to the normal multi plate transfer clutch which is why it should need the ECU to match.

The SVX would have been the only Australian delivered model to have VTD in this transmission because starting in Gen3, the auto box was updated and its a little different.

In the Gen3 Liberty, H6 Outbacks and B4 auto's as well as a few Heritage 2.5's optioned with VDC got VDC
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Current rides: 2001 Outback 2.5 Limited & 2004 Forester X
Ongoing Project/Toy: 1987 RX Turbo EJ20G, 5sp D/R AWD, 5 Stud and a whole heap of AWSOMENESS!!!
Past rides: 92 L series Turbo & 83 Leone GL Sedan
------------------------------------------
Wanted Parts:
-FWD L series shifter console (without the Lo range/4WD lever hole)

------------------------------------------
EJ wiring loom modification service for engine conversions into MY, Brumby and L series for eastern Aus. PM me for more details
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Old Tue 22nd May 2012, 11:11 AM
Liberty Valance Liberty Valance is offline
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Thanks mate, this is golden information and is starting to explain a lot of the unusual torque split behaviour I am getting from this transmission. I am still getting some rear wheel drive with the FWD fuse installed.

Almost certainly someone has put a Australian Delivered SVX transmission or perhaps an imported Automatic RS turbo transmission into my car. I can't confirm if the TCU was also swapped but I have studied the TCU wiring diagrams of both models and all the inputs and outputs match even though the colour coding is different.

I want to use this car off road so was planning to put switch on the TCU output to Duty C in order to achieve full lock up on demand but may need to reconsider how I go about that now. Initially I was was cursing this strange box but I am starting to realise it could be a very good thing. Surely the 'performance' orientation of the VTD is going to be a stronger set up that the regular MPT to handle the higher output engines?

One thing remains which is really annoying me:
With FWD fuse installed and the cruise control set at 100km/hr the transmission locks up in fourth at 2500 RPM and has enough torque to pull up long hills without unlocking.
In regular AWD mode (without FWD fuse installed) and the cruise control set at 100km/hr the transmission runs slight higher at 2750 RPM and kicks down at the slightest incline.
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Old Tue 22nd May 2012, 05:31 PM
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So did you notice binding of the driveline when turning sharp corners with the FWD fuse in our out?
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Current rides: 2001 Outback 2.5 Limited & 2004 Forester X
Ongoing Project/Toy: 1987 RX Turbo EJ20G, 5sp D/R AWD, 5 Stud and a whole heap of AWSOMENESS!!!
Past rides: 92 L series Turbo & 83 Leone GL Sedan
------------------------------------------
Wanted Parts:
-FWD L series shifter console (without the Lo range/4WD lever hole)

------------------------------------------
EJ wiring loom modification service for engine conversions into MY, Brumby and L series for eastern Aus. PM me for more details
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Old Tue 22nd May 2012, 08:44 PM
Liberty Valance Liberty Valance is offline
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I purchased the car at a heavily reduced price because it had torque bind knowing that it would be an easy fix. At that time it had permanent bind with the FWD fuse either in or out. Pretty much gauranteed the duty c solendoid wiring was faulty or the solenoid itself.

This was confirmed when I replaced the duty c solenoid and the torque bind disappeared. Of course during replacing the solenoid I began to realise this was not the original transmission for the vehicle. Through your help I now know it is VTD rather than MPT probably from an SVX or an imported RS.

Tonight I wired in a series of switches to control FWD and Duty C from the drivers seats in order to run a number of experiments. I also wired in a digital multimeter to the Duty C output on the TCU.

Comment on the TCU: I believe this is the original TCU for the vehicle. It has the large letters 'EG' marked on the front. I have seen the same lettering on other liberty TCUs from the same year. I have seen an SVX TCU for sale with the lettering 'FG'. I believe this is a different model computer.That may explain some of the weird behavour of this transmission in this car. I would be very happy to buy the correct TCU if someone could offer one.

As I understand it in a 'standard' 4EAT with MPT clutch normal behavour is:
0 Volts on Duty C = 50/50 split
12 Volts on Duty C - Front Wheel drive.
Normal driving varies volts delivering up to 90% torque to the front wheels.

In this car with 12V on duty C the wheels won't spin on wet dirt under full throttle launch.

Amazingly with Duty C switched out (0 volts) it behaves like a rear wheel drive and pulls fantastic donuts on the spot.

While this is completely opposite to what I would have expected it is also a nice suprise and great fun for offroad driving. I can live with having a switch that turns the car into rear wheel drive. Some people would kill for a feature like that in their subaru!

I'll do more testing tomorrow at highway speeds and notice the effect of switching the FWD to see what happens to TCU output volts. Still unsure why the I can't get the torque converter to lock up in AWD mode.

Another interesting observation is that the shift points in the VTD must be higher than the original box as when left in drive the car will bounce off the rev limiter in every gear under hard acceleration.

Once all this sorted my plan is to make nice daily driver which is quite capable on the beach. Mods will include X-series Forester struts and springs, 15 inch Forester rims with all terrain tyres and 50mm body and strut lift. If I can ever understand this transmission I'll wire in a couple of switches to have more control over the torque distribution.

I'm starting to get ideas that this transmission would be possible to have three modes:
1. Rear Wheel drive only
2. AWD with rear bias.
3. 50/50 split lock

Just a few teething problems to overcome first....

Cheers, Scott

Last edited by Liberty Valance; Tue 22nd May 2012 at 08:54 PM.
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Old Tue 22nd May 2012, 10:26 PM
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Its impossible to have RWD only. The reason you are getting rear wheelspin is because of the biased torque split and because the rear is lighter than the front, so the rears are the first to break traction.

So with VDT, by varying the duty cycle to duty solenoid C between 0% and 100%, you can have anywhere between a 40/60 open diff to a 50/50 locked one.

So, how did you wire these switches?
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Current rides: 2001 Outback 2.5 Limited & 2004 Forester X
Ongoing Project/Toy: 1987 RX Turbo EJ20G, 5sp D/R AWD, 5 Stud and a whole heap of AWSOMENESS!!!
Past rides: 92 L series Turbo & 83 Leone GL Sedan
------------------------------------------
Wanted Parts:
-FWD L series shifter console (without the Lo range/4WD lever hole)

------------------------------------------
EJ wiring loom modification service for engine conversions into MY, Brumby and L series for eastern Aus. PM me for more details
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Old Wed 23rd May 2012, 07:35 AM
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Not that this will help much but what I found years ago on my friends Imported RS Legacy was the rear gearbox mounts were a different shape to the aussie Liberty ones, plus the aussie RS never came in auto. We had to buy a set of SVX ones to fit it (so this is making sense now to me), so from then I, I'd always look at the rear mounts before buying a secondhand box even if the numbers were close or the same.
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Old Wed 23rd May 2012, 03:50 PM
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Wow I have never heard of VTD in a Gen1, but I guess that proves it
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Current rides: 2001 Outback 2.5 Limited & 2004 Forester X
Ongoing Project/Toy: 1987 RX Turbo EJ20G, 5sp D/R AWD, 5 Stud and a whole heap of AWSOMENESS!!!
Past rides: 92 L series Turbo & 83 Leone GL Sedan
------------------------------------------
Wanted Parts:
-FWD L series shifter console (without the Lo range/4WD lever hole)

------------------------------------------
EJ wiring loom modification service for engine conversions into MY, Brumby and L series for eastern Aus. PM me for more details
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