Page 1 of 1

looking for duty C bypass info

Posted: Mon Nov 08, 2010 6:18 am
by tahiti350
Lately I've been using my legacy as my hunting rig (it's the 214K white wagon). It's taken me places that friends with 4x4's chose not to go, but I could really use a 50/50 split on the AWD.

I've been searching for the thread that tells which wire to put the switch in to de-power the duty C, but haven't been able to find it.

Can a get an assist?

Gary B>

Re: looking for duty C bypass info

Posted: Mon Nov 08, 2010 6:46 am
by beatersubi
I've been planning on doing this soon with the coming winter.
Here's the thread I followed: http://bbs.legacycentral.org/viewtopic. ... awd+switch The better info is in the USMB thread, though.
Basically, you interrupt the signal from the TCU to the duty-c solenoid effectively locking the transfer gears in AWD/4WD.

Re: looking for duty C bypass info

Posted: Tue Nov 09, 2010 3:21 am
by tahiti350
that's the thred and info I was looking for, much thanks!! should be 4x4 for hunting this weekend!

Just to confirm, the switch selects either the Duty C solenoid or ground, correct??

Re: looking for duty C bypass info

Posted: Tue Nov 09, 2010 6:08 am
by beatersubi
From my understanding, the switch would break the signal from the tcu to the sol for 4X4 and leave it in connected for normal operation. I believe grounding it from the switch keep the tcu from throwing a code.
Please double-check, though, as I'm not 100% on that and need to re-read it myself.

Re: looking for duty C bypass info

Posted: Tue Nov 09, 2010 6:57 pm
by Legacy777
I would not recommend grounding the pin, like beatersubi mentioned the switch is simply opening the circuit which causes the duty c solenoid to be open and allow full line pressure to the rear.

According to this diagram, you could potentionally cut & hook the switch to pin 4 of the duty c solenoid and alternate that to ground. But without know exactly what the logic in the TCU is doing, I'd probably just leave it an "open" connection.

http://main.experiencetherave.com/subar ... _diag1.jpg

Re: looking for duty C bypass info

Posted: Wed Nov 10, 2010 3:23 am
by tahiti350
I wasn't talking about grounding the oin from the Duty C, but the signal lead that the switch will be in. Hoping to prevent the TCU throwing codes.

Anyone who has done the mod have the answer?

Re: looking for duty C bypass info

Posted: Wed Nov 10, 2010 4:37 am
by beatersubi
I thought I had remembered reading somewhere that grounding that signal from the tcu via the switch whilst interrupting the solenoid signal would keep the tcu from throwing codes.
I very well could be wrong, though.

Re: looking for duty C bypass info

Posted: Thu Nov 25, 2010 2:16 pm
by eulogious
Just grounding that pin will NOT prevent the TCU codes. The TCU is looking for around 13ohms (+/- about 3 ohms) coming from the solenoid, and when it doesn't see that, it throws a code. To fix the TCU from throwing a code, you need to add in a resistor pack to fool the TCU into thinking that the solenoid is still there.

When I did mine, I wired in a DPST switch, so that when I flipped the switch it broke the connection to the TCU while at the same time open a new connection to the resistor pack fooling the TCU into thinking that the solenoid is still there when it was in fact disconnected. Worked great and I had no codes ever from this.

Now there is one thing to worry about with this, and that is accidentally hitting the switch when you don't realize it and then wearing out your clutch packs. So just be care to mount the switch where you can't accidentally bump it on, and you should be good to go.

I have since modded my TCU with some DCCD code and paddle shifters and installed a knob for that allowing me to select the how much power is tranfered to the clutch pack, so I no longer use this mod. But it worked great for the 4 months or so that I used it!

Here's the thread I used over on rs25, defcon is a good guy. He helped me out when doing my mod last year!

http://www.rs25.com/forums/f8/t99075-4e ... -lite.html

Lots of good pics and info in that thread...

Hope that helps clear up some confusion!

Re: looking for duty C bypass info

Posted: Fri Nov 26, 2010 10:42 am
by beatersubi
Thanks for posting that link. Lot of good info in that rs25 thread.

Re: looking for duty C bypass info

Posted: Fri Dec 03, 2010 9:55 pm
by beatersubi
I think this thread contains enough pertinent info to be stickied. Mods?

Re: looking for duty C bypass info

Posted: Sat Dec 04, 2010 11:16 am
by eulogious
Glad I could help! It's good info to know!

At the time I had a 1990 Loyale with a 4EAT in it, so I had to find all the wires in a completely different car, and defcon helped me out with that. It a great mod to do for sure!

Re: looking for duty C bypass info

Posted: Sun Dec 05, 2010 4:58 am
by beatersubi
I just got home from the annual hatch patrol x-mas tree run up near crystal and can report with confidence that this mod is worth it for anyone who spends any time with their car off-road. I can easily see the benefit for rallycrossing, as well.

Re: looking for duty C bypass info

Posted: Sun Dec 05, 2010 8:00 am
by Danny-G
Would it be a good mod for snow drifting and mudding?

Re: looking for duty C bypass info

Posted: Sun Dec 05, 2010 9:56 pm
by Legacy777
beatersubi wrote:I think this thread contains enough pertinent info to be stickied. Mods?
Added to the sticky compilation thread

Re: looking for duty C bypass info

Posted: Mon Dec 06, 2010 3:23 pm
by beatersubi
Danny-G wrote:Would it be a good mod for snow drifting and mudding?
Yes.
Legacy777 wrote:Added to the sticky compilation thread
Thanks.

Re: looking for duty C bypass info

Posted: Sun Nov 10, 2013 12:58 am
by ashergrey
I'm preparing to do this mod on my 94 turbo wagon in advance of an extended desert off road trip. From what I'm able to gather, the duty C solenoid wire on the first gen Legacy should be the white with black stripe, correct?

Testing this wire I get 9.1 volts with the FWD fuse in and ~.1 volts with the fuse out, 1st gear selected on the lever and the throttle full open. That seems to meet the criteria from the later model FSM posted in the rs25.com thread.

Re: looking for duty C bypass info

Posted: Sun Nov 10, 2013 6:53 am
by Danny-G
Could I possibly use this mod to go rwd? If it locks the centre multi clutch pack, and I was to pull my front cvs but leave the hub ends, wouldn't that give me rwd?

Re: looking for duty C bypass info

Posted: Sun Nov 10, 2013 11:25 pm
by beatersubi
Danny-G wrote:Could I possibly use this mod to go rwd? If it locks the centre multi clutch pack, and I was to pull my front cvs but leave the hub ends, wouldn't that give me rwd?
I believe, yes, you can. Another member here (can't remember his username) recently did this with much success. edit: here it is
I would worry about transmission and rear diff durability, though.

Re: looking for duty C bypass info

Posted: Thu Nov 14, 2013 7:48 pm
by Legacy777
ashergrey wrote:I'm preparing to do this mod on my 94 turbo wagon in advance of an extended desert off road trip. From what I'm able to gather, the duty C solenoid wire on the first gen Legacy should be the white with black stripe, correct?

Testing this wire I get 9.1 volts with the FWD fuse in and ~.1 volts with the fuse out, 1st gear selected on the lever and the throttle full open. That seems to meet the criteria from the later model FSM posted in the rs25.com thread.
Yes, the white wire with black stripe should be the correct wire for the duty c solenoid.

Re: looking for duty C bypass info

Posted: Fri Nov 15, 2013 9:37 am
by ashergrey
Thank you much. I was pretty confident based on multimeter readings and examining the FSM pages but sometimes independent verification helps ease doubts.

Re: looking for duty C bypass info

Posted: Fri Nov 15, 2013 5:26 pm
by turbo970
Legacy777 wrote:
ashergrey wrote:I'm preparing to do this mod on my 94 turbo wagon in advance of an extended desert off road trip. From what I'm able to gather, the duty C solenoid wire on the first gen Legacy should be the white with black stripe, correct?

Testing this wire I get 9.1 volts with the FWD fuse in and ~.1 volts with the fuse out, 1st gear selected on the lever and the throttle full open. That seems to meet the criteria from the later model FSM posted in the rs25.com thread.
Yes, the white wire with black stripe should be the correct wire for the duty c solenoid.
so if i tap into this wire with a 2 way switch i could use it for power mode?

Re: looking for duty C bypass info

Posted: Sat Nov 16, 2013 2:41 am
by Danny-G
Power comes from grounding a pin from the TCU.

Re: looking for duty C bypass info

Posted: Mon Nov 18, 2013 12:22 am
by Legacy777
turbo970 wrote:so if i tap into this wire with a 2 way switch i could use it for power mode?

This was in the forum sticky

http://bbs.legacycentral.org/viewtopic.php?t=34807