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06 XT Forester
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68 Posts
Discussion Starter · #1 ·
So I've gone ahead and swapped out my MPT " center diff" to a VTD.
All is good and it drives great. I've read through the threads on the swap and as far as I can tell the flashing AWD light is because of the wheel speed sensor.
any help with deciphering this and advice on what to do would be much appreciated.

Cheers.
 

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2010 2.5X Manual
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311 Posts
I have pondered the swap on my '03, one thing that could be done is to cut a new tone ring to go on the output shaft, the sensors are the same (on my '03) but the VTD tone ring has fewer teeth than the MPT clutch basket has ridges.

There is some thought the freeSSM app can tweak some parameters to make it work.

As I type this it occurs to me maybe the front sensor could be wired to both the front and rear sensor wire?
 

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06 XT Forester
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68 Posts
Discussion Starter · #4 ·
Mr duderotemy.... Can you tell me what you swapped out. It was uncharted territory for the guy who did mine. I've tried to contact a6d6e6 as he seemed to have the same issue. Sounds like it was the wheel speed sensor but he lived with it. I hope it's just a sensor that needs a resistor to keep it quiet. It would be good to hear from others that have done the swap.
 

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06 XT Forester
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68 Posts
Discussion Starter · #5 ·
Any one else made this swap. I would like to hear your experiences.
Cheers.
 

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06 XT Forester
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Discussion Starter · #6 ·
"As I type this it occurs to me maybe the front sensor could be wired to both the front and rear sensor wire?"

Could this work?
 

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2010 2.5X Manual
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311 Posts
If you can turn up some details on how the sensor works that would help figure out if they can be tied together.

For example, if it is +12V and a sense lead, a ground and a sense lead, or a high impedance differential input.

Or the technology type- hall effect, etc...
 

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2007 XT Sport 5MT
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24,014 Posts
Mr duderotomy.... Can you tell me what you swapped out. It was uncharted territory for the guy who did mine. I've tried to contact a6d6e6 as he seemed to have the same issue. Sounds like it was the wheel speed sensor but he lived with it. I hope it's just a sensor that needs a resistor to keep it quiet. It would be good to hear from others that have done the swap.
Mine was a case of pulling the old 4.444FD MPT transmission and replacing it with a 4.111FD VTD transmission and matching differential.
On my older 2002 setup there weren't any wheel speed sensor issues as the system didn't require them in my original chassis since I didn't attempt to use the VDC system to control the brakes individually.
 

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06 XT Forester
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68 Posts
Discussion Starter · #10 ·
I see.... So you swapped the whole transmission. I only swapped out the mpt clutch.
Now to find out more about this pesky light. Thanks cny_dave.
 

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2010 2.5X Manual
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311 Posts
If the Dude didn't have the problem, that suggests the VTD trans front VSS tone ring has a different number of teeth than the front tone ring for the non VTD trans. Or it's the same, and he got lucky somehow!

The harnesses and sensors are the same, I've been told.
 

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06 XT Forester
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Discussion Starter · #12 ·
Ok then..I started a more specific ( I hope ) thread to try and chart a solution. Is the wheel speed sensor for the VDC which I don't have so could it be kept quiet with the right resistor.... Or not? It would be grand to be that simple.
 

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2010 2.5X Manual
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Both the VTD and the MPT use both the front and rear VSS's to track relative wheelspin.

With MPT below a certain speed the MPT clutch will be locked up more if it senses front wheelspin.

The sensor senses ridges in a chunk of metal moving past the sensor, sending either a voltage or a current signal.
 

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06 XT Forester
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Discussion Starter · #14 · (Edited)
Thanks a mill. For getting on board.

So am I right in thinking then that VTD AS a mechanical gear set not the " plates " of the MPT it's physically coupled and not engaged by oil pressure so the speed sensor is now redundant?
The LSD component is operating. As controlled by the duty c solenoid..... Which is a good thing.

Thoughts?
 

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2010 2.5X Manual
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311 Posts
The rear speed sensor isn't needed in your case, yes.
When there is no front or rear slip the power is coupled through the VTD planetary diff.
The TCU doesn't know that, of course.

What is normally done with this swap is to disconnect the transfer duty solenoid from the TCU and put in a manual switch, because the TCU is going to be locking up the clutch after the VTD section needlessly, perhaps causing it to give torque bind after awhile.
The VTD clutch is not designed to slip a bit all the time, it is designed to be locked or unlocked. It is just like the MPT clutch but has fewer plates.
 

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2004 Forester XT 4EAT SportShift
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Or you can find a TCU from a VTD vehicle. Mine has the flashing FWD light as well. But that is because my TCU came from a VTD car but my transmission is still MPT. I need to source the VTD from a WRX some how to fix this and get 45/55 split.
 

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2010 2.5X Manual
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For my outback, you could only get VTD with VDC and the TCU cannot be swapped over, half the dang car harness is different.

For MPT-VTD swaps where the model was avail with MPT or VTD without VDC, a TCU swap at least seems feasible.
 
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