MUDRAT's Manual to Auto conversion thread

MUDRAT · Post by **MUDRAT** » Fri Dec 30, 2005 3:56 pm

Basically, I want to remove my dual-range 3.9:1 5MT and replace it with a 4.44:1 geared automatic with a front LSD.

What we have established so far:

They're bloody big gearboxes for an L series
They suck heaps of power
They're not so good down hills off road

What we still need to know:

What front driveshafts could I use?
What's the best TCU to make this sucker work?
Which torque converter would best suit a NA EJ20?
Can we lock the converter at will?

Now I'll hand you over to our AT gurus, SteveRisingSun and VincentVega:

PeeJay · Post by **PeeJay** » Fri Dec 30, 2005 4:12 pm

The 4.44 Autos are from the early Legacy turbos right? If so I've got one kicking around with it's TCU that could use a new home.

You're right, it's a massive beasty!

smoov · Post by **smoov** » Fri Dec 30, 2005 4:46 pm

what I want to know is:

Which cars did they come in? I'd like something with the 4.44:1 already in it, so I could modify the car around it.

Forester?
Outback?

year models?

Ben · Post by **Ben** » Fri Dec 30, 2005 5:44 pm

You can lock any of the duty cycle solenoids, line pressure and torque convertor are included - ie you could flick a switch and stall the motor at idle if you wanted...

steve_rising_sun · Post by **steve_rising_sun** » Fri Dec 30, 2005 6:01 pm

These boxes use the RX size inner CVs.
Use the turbo converter that comes with the box. Its possible a EJ16/18 may be smaller for the big launch.
Go for the NA TCU and wiring. Easy to get, cheap, right shift points.
You wont have a reed switch, I will look up any side affects on Tues
If you are not using the factory ECU or because of the reed switch you may not get lock up clutch automaticlly, easy to hook up a switch, dito for lock up rear and full line pressure.
I have not seen a front LSD?
Steve

vincentvega · Post by **vincentvega** » Sun Jan 01, 2006 5:56 am

damn thats a shame we lost that thread.

I am in canada at the moment but look forward to continuing this with you guys when i get back!

The biggest question i have is how the AWD behaves with the dutyC solenoid disconnected in the planetary box. Does it just behave as a normal open center diff AWD ?

I have been trying to get some info about htis out of Al from sunspares. he seems to think it wont work but i dont understand why (and you have obviously done it steve)

see here
http://www.rslibertyclub.org/forums/sho ... hp?t=54479

Ben · Post by **Ben** » Sun Jan 01, 2006 9:41 am

When the rear clutch pack (DC C?) has 0 volts across it, it is completely locked up in 50/50 drive. With 12v across it, it is completely open. When I was talking to SS guys at the bbq last year their impression was that it wouldn't work too (I pretty much resigned myself to 5 speed at that then - which is unusual for me)

I have the 8 bolt motor though, will that cause problems making a early EJ auto fit?

daza · Post by **daza** » Sun Jan 01, 2006 10:17 am

Hey peoples,
listening to you guys makes me wonder, It sounds like this DutyC solenoid is feed a PWM signal from it's TCU? if that's the case then wouldn't it be simple to just rig a variable 555 PWM off a linear pot to give a slider that's 1% rear drive all the way forward and 99% rear drive all the way back? Oh and, see below

<Disclaimer> Don't like Auto's, Don't know Lib's, please ignore me if i'm making no sence

</Disclaimer>

PeeJay · Post by **PeeJay** » Sun Jan 01, 2006 11:05 am

What I wanna know is how to put an active center diff in a 5sp dual range!

steve_rising_sun · Post by **steve_rising_sun** » Sun Jan 01, 2006 7:13 pm

If you just leave solinoid C disconnected on the planitary box it will only flash up a fault code on start up [big deal] On the normal box you would be locked in 4WD. Shifts will be the same. You should be able to use this trans on a 8 bolt engine.
Steve

vincentvega · Post by **vincentvega** » Mon Jan 02, 2006 7:11 am

MechaWagon wrote:When the rear clutch pack (DC C?) has 0 volts across it, it is completely locked up in 50/50 drive. With 12v across it, it is completely open.

Thats on the gen1 autos like my car. The later planetary boxes are what were talking about here. They are opposite - 12V on the solenoid locks teh rear drive, 0v on the solenoid - havnt worked out that one yet! although steve thinks it works, i still dont understand how

If you had the choice either way, you wouldnt want to use an early box for your offroader, the center clutches are too weak. That said i havnt burnt mine out yet, but scott has fried 2 sets in his turbo lib..

vincentvega · Post by **vincentvega** » Mon Jan 02, 2006 7:18 am

daza wrote:Hey peoples,
It sounds like this DutyC solenoid is feed a PWM signal from it's TCU?

correct. its a 50hz PWM and the duty cycle on the solenoid is varied from 19/20 (FWD) to 1/20 (50-50 lock) - im talking a gen1 clutch box here

if that's the case then wouldn't it be simple to just rig a variable 555 PWM off a linear pot to give a slider that's 1% rear drive all the way forward and 99% rear drive all the way back? Oh and, see below

You could do something along those lines, although you would need a higher current driver to actually drive the solenoid (it pulls about 1amp). If you were to spend some time monitoring the output of the proper planetary box computer then you could probably come up with quite a decent controller

MUDRAT · Post by **MUDRAT** » Mon Jan 02, 2006 8:07 am

I mean all this is awesome theory, but is the TCU that comes with the box just not up to handling the task for off-road? Do you need that level of control over the rear drive?

Outback bloke · Post by **Outback bloke** » Mon Jan 02, 2006 8:09 am

What is the need for this solenoid mod? Is it to stop that slipping between front and rear that Twinkles car is so good at? If so, didn't the later model boxes sort that out as you have said? What would be the need to do it if that is the case?

jzk25 · Post by **jzk25** » Mon Jan 02, 2006 9:17 am

We need to confirm some facts here before people get the wrong ideas into there heads and waste there time/money.

I am not an electronics expert but I am a Subaru expert

. I have also dealt with all types of subaru autos as well as swapping transfers between boxes and monitoring the solenoid activity with the select monitor.

If you have a solenoid failure on a non turbo car without VTD you are left with fwd only, this would equate to having 0v to the solenoid.

If you have a solenoid failure on a turbo car with VTD you are left with a locked driveline, this would also equate to having 0v at the solenoid.

So applying 12v to a VTD car removes the rear drive bias.
Applying 12v to a normal transfer gives a locked driveline.

The thing with a VTD transfer is it has a centre differential as well so it is still awd without the clutch pack operating but it is like an open diff, the drive will go to the pinion with the least traction.

Unless I am missing something I believe this to be correct.

steve_rising_sun · Post by **steve_rising_sun** » Mon Jan 02, 2006 9:05 pm

jzk25 wrote:We need to confirm some facts here before people get the wrong ideas into there heads and waste there time/money.

I am not an electronics expert but I am a Subaru expert . I have also dealt with all types of subaru autos as well as swapping transfers between boxes and monitoring the solenoid activity with the select monitor.

If you have a solenoid failure on a non turbo car without VTD you are left with fwd only, this would equate to having 0v to the solenoid.

If you have a solenoid failure on a turbo car with VTD you are left with a locked driveline, this would also equate to having 0v at the solenoid.

So applying 12v to a VTD car removes the rear drive bias.
Applying 12v to a normal transfer gives a locked driveline.

The thing with a VTD transfer is it has a centre differential as well so it is still awd without the clutch pack operating but it is like an open diff, the drive will go to the pinion with the least traction.

Unless I am missing something I believe this to be correct.

You are missing something.
The NA 4AT auto uses solinoid C to release the rear clutch, if it fails you get locked 4WD- fuse or no fuse
The planetary boxs is full time AWD until you power solinoid C. You then get full time 4WD so its back the front to a NA box
The planetary gearset works the same as a Pagero Super Select or Rangie ie drive is transmitted through the rear until the rear 'slows' ie a corner causing the third member to 'roll over'
Do it Muddie I am
Steve

MUDRAT · Post by **MUDRAT** » Mon Jan 02, 2006 11:18 pm

Yeah I'm seriously considering . . . I have seen aftermarket Torsen-type front LSDs for Subies and didn't some of the STi Imprezas come with front VLSDs?

Coupled with the Haultech traction control it should make a formidable beast!!

steve_rising_sun · Post by **steve_rising_sun** » Tue Jan 03, 2006 5:57 pm

The auto front diff is very narrow are you sure they make a slip diff for them?
Steve

MUDRAT · Post by **MUDRAT** » Tue Jan 03, 2006 7:45 pm

No I'm not sure about the auto, I just went on assuming they were the same as the manual front diff.

Ben · Post by **Ben** » Tue Jan 03, 2006 9:13 pm

And just for my own piece of mind.....

The planetary boxs is full time AWD until you power solinoid C. You then get full time 4WD so its back the front to a NA box

So this is like a EA82 awd gearbox, only instead of having a dog tooth diff lock there is a clutch pack which under power from the solenoid will give varying degrees of lock to the centre diff?

If so, that is just about the most awesome thing ever.........

Where do I get a box to suit my 8 bolt motor, and how much are they?

Is this what the auto in my Gen III Liberty is? No wonder I can't get the thing bogged...