91 legacy 4EAT diff lock switch

[Markus56]

So i have read about 10 different threads on various subaru boards, and i still cannot determine where the wire to splice into for the diff lock is.

 

The only thread i found with pictures is old enough to not display them, and there isn't anywhere that says what color the wire is or anything.

 

 

I did find one thread that said to splice the green wire w/ red stripe behind the passenger kickpanel, and that turned out to be the driver side auto seatbelt wire .

 

So has anyone who has done this mod on a first gen legacy help me out here?

 

Thanks

[Markus56]

ok.

 

 

figured it out.

 

the brown wire on the TCM wire bundle.

 

 

 

 

 

Edited August 23, 2010 by Markus56

[98obster]

sweet. i have the same switch. yeah, i'm sure andyjo's pics are long gone-good job. the fastest i've ever driven with it "engaged" is around 15-20 mph mostly for monster snow fall-haven't used it for a while though. just be sure you soldered and shrinkwrapped the connections and at the switch too-you don't want that circuit to open unless you flip the switch.

[Markus56]

Just used some butt connectors. i might use some electrical tape if i can get to it later

[idosubaru]

woah what a crazy looking switch, what is that? is it lighted?

 

what was originally in that slot?

[Markus56]

its a switch with a flip down cover i bought at O'rielly's. no lights, just the sun was lighting it funny.

 

 

What ever was there did not come as an option in my car

[wtdash]

 

What ever was there did not come as an option in my car

 

 

Neither did mine ('90 L Wagon), but I think it's for the Height Adjustment avl. on the LS/LSi models?? Yep - see below. (sorry for the off-topic Hi Jack)

 

Also, for posterity sake here's the LINK to the USMB's Repair Manual thread on this. Although the pics are 'dead' the description is still pretty good and he gives a diagram of the pin-out to ID the correct wires.

 

This worked great when my tranfer clutches were causing issues and I had a delay in AWD....w/this mod I just hit the switch (when it was slippery) and had AWD all the time.

 

 

Edit: Found a pic Thanks to Legacy777:

Td

Edited August 25, 2010 by wtdash

[WoodsWagon]

I would have recommended cutting in to the c soleniod wire at the TCU connector, that's right above your feet under the dash. That would have put the splice inside the passenger compartment, protected from the weather, and shortened up your wiring by a fair bit, as well as removing chafe points where your wire is likely to get rubbed through, short to ground, and fry the TCU. But that's just me.

 

You can use a double pole switch that shunts the signal from the TCU to a dummy load, that will keep the TCU from throwing codes. There's a writeup on building the dummy load around here somewhere.

[Slamngears5]

Im going to sound like a complete idiot but what are the advantages and disadvantages of doing this and does it lock all four wheels in drive im sorry im clueless on this im used to newer subarus and this is all so new to me

[Manarius]

Im going to sound like a complete idiot but what are the advantages and disadvantages of doing this and does it lock all four wheels in drive im sorry im clueless on this im used to newer subarus and this is all so new to me

It switches the duty cycle of the solenoid c in the transmission to 100% (or 0%, I forget which) in order to force a 50-50 torque split between the front and rear wheels.

[idosubaru]

it essentially "locks" your front and rear wheels. but it's sort of complicated too.

 

AWD or 4WD has power split from front to back.

rear has power split to right and left wheels via rear differential.

fronth has power split to right and left wheels via front differential.

 

this mod only controls the first power split which happens in the trans for subarus. this gives you "locked" front to back.

 

if you have open diffs front and back that means 2 wheels getting power.

 

if you have locking rear you can have 3 wheels getting power.

 

very rare, but possible to have a locking front diff. none come stock like that except possibly WRX STi.

 

and then it gets even more complicated than that.

[Slamngears5]

Ok i understand... Ive just been around 2002 and up Imprezas WRX and STi's 2005 and up Legacys i wasnt sure how this mod worked on my 92 legacy wagon what is the max speed you can maintain with this mod??

[98obster]

Ok i understand... Ive just been around 2002 and up Imprezas WRX and STi's 2005 and up Legacys i wasnt sure how this mod worked on my 92 legacy wagon what is the max speed you can maintain with this mod??

 

Go ask Andyjo, ha. IMHO, this isn't a switch to go Rallyx in. At most, it might be a crawl assist in 3 ft of freshy snow or up a muddy incline. Probably 15-20 mph would be my guess. at that speed you would probably still be in 1st anyway which still maintains the 50/50 torque split but you can have it in D and when you get going you can close the switch and be on your way. IIRC, there is a slight lag in the TCU when starting out as it determines the amount of torque to put to the rear, the switch just pretty much gets rid of that lag. not as big a deal as it sounds though, I've never had a problem getting around without the switch. Going up Fall River Road in Rocky Mountain National Park in a week or so, and I will see if I can tell any significant difference

[Manarius]

If you put the auto selector at the "1" and put the manual button on, you're guaranteed to get 50-50 split anyway because this what the TCU is designed to do. You'll also get 50-50 split in reverse as well, regardless of condition or manual button.

[Markus56]

It's only about 60-40 that doesn't work in reverse, and in my car it only cycled power to the rear end to find traction. At the time, my front end was bottomed out on some ruts in a cabbage field. The switch makes life easier.

[johnceggleston]

the tcu and the transfer clutch ALWAYS allow for some slip between the front and rear. it is never locked in a 50 - 50 split. this is designed to avoid binding even when you need extra torque to the rear. but the system does put out it's maximum to the rear when called for and it is one of the best systems on the road.

 

the switch removes the brain and the designed slip from the system, it locks the rear drive shaft to the front output shaft and they both turn at the exact same speed, no slipping allowed. this is great for rock crawling, mud, sand, snow and other places where you need 4wd but not good on pavement.