Successful inversion of Transfer Solenoid signal

[CNY_Dave]

Ongoing saga of a 2004 4EAT in a 2003.

2004 has max lockup with the transfer solenoid driven at +12V, min at 0V.

2003 is the opposite- no juice and it locks, +12V to disengage.

I successfully used an inverting solenoid driver to invert the signal,
that is, turn the 2003 signal of little blips to 0v for a little lockup
and longer blips to 0v for more lockup into little blips to +12V for a
little lockup and longer blips to +12V for more lockup.

(In reality it is a 50Hz pulse-width-modulated signal).

The outcome is about what I thought- it is driveable, doesn't seem to
bind on tight circles, and it is sufficiently locked when I need it to
be (still some snow about for testing), but it isn't quite right.

In D from a standing start in snow it will spin for a moment then engage
with a bang, and if I drive through snow slowly it will bang on and
bang off. Fortunately it engages nice and smooth in 2 and 1, so I can
live with it.

On wet pavement, planting the gas from a standing start works OK with no bang.

So, it's not 100%, and I need to drive it a bit to make sure nothing
weird happens, but for my 200,000 mile subie I can live with it.

Of course some of the symptoms might be from a trans that has seen some
torque bind, or perhaps the clutch baskets are grooved a bit. Not in the
mood for further teardowns this season, though.
       

Edited February 28, 2013 by CNY_Dave

[Legacy777]

Dave,

 

Thanks for sharing.  That's interesting.  I didn't know they changed style transfer solenoids.

[johnceggleston]

 

2004 has max lockup with the transfer solenoid driven at +12V, min at 0V.

 

 

2003 is the opposite- no juice and it locks, +12V to disengage.

i'm trying the learn and understand so help me if you can.

 

setting the electricity aside for a moment,

 

no fluid pressure = no power to the rear, no connection front ot rear. this is confirmed by jacking up one rear wheel with the engine off and spinning it by hand.

fluid pressure to the clutch =  power to the rear.

 

it was my understanding, in the 90s, that the duty c was a ''duty'' solenoid, and by definition, that was a cycly on / off operation with the cycle rate determined by the TCU? is this incorrect? i never knew a voltage difference played a part. i thought it was a cycle rate, like cycles per minute.

 

and the rate of the duty cycle, 10% - 90% ????, determined how much fluid pressure, to the cluctch and therefor how much power to the rear.  more fluid pressure meant more power.

 

the thing that is confusing : the more electrical power tot the duty c, the less fluid pressure. zero electricity to the dutyc menas maximum fluid pressure, maximum power to the rear.  it just seems backwards but that is the way it is, for the 90s.

 

and with the FWD fuse in, again 90s, the dutys was ''always on'' or perhaps more correctly, 100% duty cycle. this rate would bleed off all fluid pressure and create FWD. right so far?

 

cut the power to the duty c and you got full fluid pressure an 4WD ''locked''.

 

so did they change the fluid system, or did they change the action that bleeds off fluid pressure?? or are they the same thing?

 

and what ever became of the aussie? cars that had a 4WD fuse under the hoods. fuse in = 4WD locked? nipper, do you remember this?

 

 

a lot of questions in a fairly confusing manner, sorry.

[CNY_Dave]

I am investigating how they brought the change into effect, as I may be able to swap in parts from my '03 trans.

 

I think what did NOT change was that the MPT clutch (MPTC for short) locks up when fluid pressure is applied, and slips when it is not. Changing that would require a lot of changes to the hydraulic system.

 

in '03 and in '04 the solenoid has a built-in little valve that manipulates pressure in a pilot line, that pressure then controls a larger valve which connects the MPTC to full line pressure or do a dump port.

 

I know in both cases the solenoid is given bursts of current.

For '03 the current is mostly on, with short little pulses of the current off (connected to +12V or ground). Constant +12V releases the MPTC, constant 0V fully engages the MPTC.

 

For '04 the current is mostly off, with short little pulses of the current on. Constant 0V fully releases the MPTC, constant +12V fully engages the MPTC.

 

I assume the hydraulic valve sits in one position for a given signal to the solenoid, but that's an assumption.

 

http://www.ultimatesubaru.org/forum/index.php?app=core&module=attach&section=attach&attach_rel_module=post&attach_id=7458

 

Now, I think in '03 +12v to the solenoid dumps pressure from the line to the main valve, allowing the main valve to move to the right and connect the MPTC to the dump port (labeled 'X'). This means in '03 the solenoid valve is closed by default, and opened by power.

 

In '04 they could just have made the solenoid normally 'open' and +12V closes it, then I'd just have to change the solenoid. Or maybe the solenoid is the same but the valve is different. or maybe both are different.

 

If I can find a 2004 manual with the schematic page, I'll be pretty much golden on figuring it out.

Edited March 1, 2013 by CNY_Dave

[CNY_Dave]

I believe the part I colored green is the moving part of the valve, and it has a spring on the left side pushing it to the right.

 

 

 

[CNY_Dave]

I have started the solenoid-valve swap process.

Compared to the '03 the trans case and extension case of the '04 look
identical, the solenoid, valve, and plate are visibly different upon
close inspection.

Work so far has been delayed by a snapped case bolt (drilled and heli-coiled) and the wrong case gasket.

Am crossing fingers the valve swap will work out.

Heck, right now am crossing fingers it all goes back together

[CNY_Dave]

Put in my '03 transfer duty solenoid, transfer valve, and transfer valve plate.

 

Seems to be working just fine.

 

No leaks. Yet.

 

Do I dare try the FWD fuse?

[Legacy777]

Dave,

 

Thanks for the update.  Did you take any pictures during the work you did?

[CNY_Dave]

I have some pics, haven't smallified them yet.

 

I think it will be the very first pics of an '04+ valve.

 

I can ID an '04 valve etc by sight now, another singularly useless skill!

[CNY_Dave]

2003 Solenoid

 

2004 Solenoid (has 2 o-rings)

 

2004 vs 2003 plates ('04 on left)

 

2004 vs 2003 valves (2004 on left)

Thought I had a pic of the '04 valve where the solenoid sits, guess not- the bore has 2 different diameters and there is a small passage (hole) drilled in the side of the bore.

Edited November 18, 2013 by CNY_Dave

[Legacy777]

Cool!  Thanks for the follow up and pics Dave.

[johnceggleston]

so just to review,

you installed your 03 duty c and valve assembly into your 04 auto trans and you eliminated all the headaches you had been suffering.

 

so this means an 04 auto trans will swap into an 00 - 03 car if you swap the duty c & valve assembly, right?

Edited November 20, 2013 by johnceggleston

[CNY_Dave]

Yes, swap in the solenoid and valve and valve plate under the valve. Connector etc is the same.

 

Probably of more use to someone with an '04- that's a 1-year only trans!

 

I have an '04 valve etc if someone needs to do that someday.