dreedraffs Posted January 6, 2007 Share Posted January 6, 2007 I red somewhere that the AWD is an electric (electronic) one in older Legacies. How does it actually work? Is it somekind of temporary AWD or is it a full time AWD that changes the front/rear power transfer. I red it is possible to remove the fuse so that the AWD will not work and the car will get stucked in FWD mode. What I'm wondering is if the opposite can be done too, bypassing the electronics somewhere to get the car stucked in 50/50 mode. So I'd need to know how the AWD works on those car to figure out what can be done. Why I'm asking this is I have a '00 manual Impreza and I had a '92 4WD Loyale. I did prefer the 4WD on the Loyale that the AWD on the Impreza. It is pretty nice to have a real 50/50 (locked) power transfer. So I'm wondering if there's a way to get the 50/50 on an automatic Legacy with a small modification in the electronic control. I don't have the money for a DCCD, so I'm looking for a cheap alternate. Link to comment Share on other sites More sharing options...
Manarius Posted January 6, 2007 Share Posted January 6, 2007 Search. It's been covered many times. Use something like "Solenoid C" and "50/50". Link to comment Share on other sites More sharing options...
nipper Posted January 6, 2007 Share Posted January 6, 2007 This has been discuseed many many many many times. Its not as simple as adding a switch. Most people (there is only one with any success) who do this mod end up with a 1000.00 repair since the AWD unit tears itself apart. The computer does a very good job of applying AWD in all conditions, so there really is no reason to overide it. These arent rock climbers. Also its not something to do if you dont understand how the system works. The FWD fuse is meant for emergencies, or if the AWD is screwed up and you can't afford to get it fixed at that time. The fuse can work from a month to a few years. The fuse sends a signal to the TCU to energize the duty c solenoid fully, which it is not designed to do. Now since this is in the older generation of subarus, I am not sure if you are asking about the AWD, or the push button 4wd. nipper Link to comment Share on other sites More sharing options...
Manarius Posted January 6, 2007 Share Posted January 6, 2007 This has been discuseed many many many many times. Its not as simple as adding a switch. Most people (there is only one with any success) who do this mod end up with a 1000.00 repair since the AWD unit tears itself apart. The computer does a very good job of applying AWD in all conditions, so there really is no reason to overide it. These arent rock climbers. Also its not something to do if you dont understand how the system works. The FWD fuse is meant for emergencies, or if the AWD is screwed up and you can't afford to get it fixed at that time. The fuse can work from a month to a few years. The fuse sends a signal to the TCU to energize the duty c solenoid fully, which it is not designed to do. Now since this is in the older generation of subarus, I am not sure if you are asking about the AWD, or the push button 4wd. nipper Yeah, I didn't want to beat the dead horse with this one, but doing the "switch" method to doing 50/50 with the AWD isn't good for the system. I just wanted to point him in the right direction if he wants to take that risk. Link to comment Share on other sites More sharing options...
Gloyale Posted January 7, 2007 Share Posted January 7, 2007 I have an early AWD GL. Back then it was "fulltime" 4wd but basically the same. I have mine set up with a switch. It is inline in the duty solenoid c (or transfer solenoid)circuit. I leave it on(closed) normally so that the system functions with standard AWD control. When I am in deep snow or mud i can turn the switch off(open) so that no signal goes to the transfer solenoid. with no signal the solenoid does not operate. This means full torque is applied to rear wheels. FSM even refers to it as "locked" although only descibes it as default when the solenoid fails. I accessed the cicuit from the connector in the pass.(right) side kick panel. It is also easily done at the trans connector as well but then you have to run wires through the firewall. Basically you just find the wire going to the solenoid. Make sure you've got the right one. A good pinout of your excact year and model is important for this. once you're sure, cut it. Then run a wire(same gauge) to your switch and back. splice one end to each of the cut ends. you just want the switch to interupt the cicuit. just there and back It is important not to drive in the locked(switch off) mode on pavement. Or even in the mud and snow unless you really need it. If you do you'll wreck the transfer clutch from to much pressure. But you can definately feel that the rear gets more grip especially from a stop or in an "understeer" slide. I also ran another switch by tappin into the FWD fuse connector so I can turn on the FWD from inside. I used an inline fuse on the wire just so there still is a fuse. Mostly for diagnostic, because you have to put it in FWD to read the codes. But that is really a seperate affair and not needed to do the lock thing. BTW the AWD on manual transmission subies uses geared, or viscous, conventional differentials. totally different from the auto trans setup. The switch thing does not apply to manuals. Link to comment Share on other sites More sharing options...
daeron Posted January 7, 2007 Share Posted January 7, 2007 wrong forum??? I didn't read every word, but legacy != older generation of subarus. Link to comment Share on other sites More sharing options...
NorthWet Posted January 7, 2007 Share Posted January 7, 2007 ... I have a '00 manual Impreza and I had a '92 4WD Loyale... Manual transmissions do not have electric/electronic control. The AWD used in the New Gen (Legacy/Impreza/Forester) manual trannies use a central differential with a viscous coupling. All the talk about electronic control, Duty "C", and FWD fuse only apply to the automatics. Link to comment Share on other sites More sharing options...
calebz Posted January 7, 2007 Share Posted January 7, 2007 Moved Link to comment Share on other sites More sharing options...
dreedraffs Posted January 8, 2007 Author Share Posted January 8, 2007 I know the electronic stuff is only on automatic EJ models. I said a word about my manual '00 Impreza and my previous '92 Loyale to compare the viscous AWD next to the T/C 4WD, which I prefer. And as I like to have a 50/50 in snow, I might get an automatic Legacy if I can trick it out to turn the 50/50 on/off as I want. I refered to ''older'' Legacies as I don't know how the newer ones work. I'm in Quebec and the 50/50 thing is just to get a little more fun out of the car when we get enough snow. I don't want a hill climber and I'd only use the 50/50 thing in snow. After driving the Loyale for a winter, I thought I'd like to have something that would go throught almost anything. And after a few months with a Lada Niva, I realize that what I really like is a car with a good feeling (brakes, steering, power) and a locked 50/50 system. A DCCD is too expensive and full time 4WD as in RX/II models is getting too old. So there's not a lot of choices here... I'm not a newbie whe it comes to car. I don't know how the automatic trannies AWD system works, but only because I did not red about it. If I could find a tech sheet about this I'd go through. I just wanna know how it works to find out what can be done with it. Link to comment Share on other sites More sharing options...
kimokalihi Posted January 8, 2007 Share Posted January 8, 2007 legacy != older generation of subarus. No it doesn't. Legacys are new generation subarus. It lists the cars that are in each section on this site and legacy's are in the new generation section. Link to comment Share on other sites More sharing options...
dreedraffs Posted January 8, 2007 Author Share Posted January 8, 2007 So, from what I red on the forum. ''Something'' (which I did not figure out yet) sens information (volts) to the selenoid C that controls the hydraulic pressure applied on clutches. Depending on the pressures applied on clutches, the torque transfer varies from 90/10 (f/r) to 50/50. Quite simple. Where does the system takes the information about what the torque transfer should be? I mean, what sensors detects the condition/wheel spin. I will have to try an automatic Subaru. With a standard 90/10 ratio varying to 50/50 it sounds like a part time AWD like those in CRVs and Rav4. Link to comment Share on other sites More sharing options...
johnceggleston Posted January 8, 2007 Share Posted January 8, 2007 So, from what I red on the forum. ''Something'' (which I did not figure out yet) sens information (volts) to the selenoid C that controls the hydraulic pressure applied on clutches. Depending on the pressures applied on clutches, the torque transfer varies from 90/10 (f/r) to 50/50. Quite simple. Where does the system takes the information about what the torque transfer should be? I mean, what sensors detects the condition/wheel spin. I will have to try an automatic Subaru. With a standard 90/10 ratio varying to 50/50 it sounds like a part time AWD like those in CRVs and Rav4. there are 2 speed sensors on the trans. one on the front differentils and one one the rear output to drive shaft/rear differential. the TCU or ECU detects the speed difference it sends more power to the rear wheels. the flow of A/T fluid is metered by the 'duty c' solenoid. when the duty c fails the trans goes to locked 50/50 slpit which gives you torgue bind. when the FWD fuse is installed, under the hood, the duty c is 'always' on and you get power to front wheels only (FWD). i don't know the crv or rav4, but this is all wheel drive all the time not part time. if you install the FWD fuse and drive the car you can feel a distinctive differenc in the way the car handles and drives. therefore even with a 90/10 split it makse a huge difference in how the car drives. the few times i have tried this it makes the car feel 'squirrely' or 'lose'. but this is only because it's then FWD only and how great it drives with AWD. Link to comment Share on other sites More sharing options...
nipper Posted January 8, 2007 Share Posted January 8, 2007 there are 2 speed sensors on the trans. one on the front differentils and one one the rear output to drive shaft/rear differential. the TCU or ECU detects the speed difference it sends more power to the rear wheels. the flow of A/T fluid is metered by the 'duty c' solenoid. when the duty c fails the trans goes to locked 50/50 slpit which gives you torgue bind. when the FWD fuse is installed, under the hood, the duty c is 'always' on and you get power to front wheels only (FWD). i don't know the crv or rav4, but this is all wheel drive all the time not part time. if you install the FWD fuse and drive the car you can feel a distinctive differenc in the way the car handles and drives. therefore even with a 90/10 split it makse a huge difference in how the car drives. the few times i have tried this it makes the car feel 'squirrely' or 'lose'. but this is only because it's then FWD only and how great it drives with AWD. Thats pretty accurate except one or two points. The Duty C solenoid works in conjunction with a spool valve inside the transmission to vary not only the period the solenoid is on, but also the pressure to the clutches. This is where the dash switch to get manual AWD fails so badly. People dont always take that part of the circuit into considertaion. You can force 50/50 split under three conditions, Reverse, Low, and ful throttle. In the newer cars there is a G sensor and the steering angle sensor also incorporated into the system. I know in the older cars there is also a G sensor under the console, which i think is either part of the AWD or ABS or both (can't get an answer on that). nipper nipper Link to comment Share on other sites More sharing options...
Gloyale Posted January 8, 2007 Share Posted January 8, 2007 You can force 50/50 split under three conditions, Reverse, Low, and ful throttle. nipper I have mine set up with a switch. In sand or snow, with the switch on(normal), I get a fair amount of spin in front before I can feel the back kickin in. When it does it seems to be not quite enough. When I flip the switch off(locked) the difference is felt immediatly, regardless of what gear I'm in. works at all throttle conditions too. This is not just a theory, this is actually how my car works. Link to comment Share on other sites More sharing options...
nipper Posted January 8, 2007 Share Posted January 8, 2007 I have mine set up with a switch. In sand or snow, with the switch on(normal), I get a fair amount of spin in front before I can feel the back kickin in. When it does it seems to be not quite enough. When I flip the switch off(locked) the difference is felt immediatly, regardless of what gear I'm in. works at all throttle conditions too. This is not just a theory, this is actually how my car works. Mine isnt theory either (its from observation and the factory manual). MY 97 with a NEW awd unit kicks in very quickly. People seem to forget (or unreasonably expect) things to last for ever, which they dont. Be it the AWD, headgaskets, engine, or transmission they do wear out (some sooner then others). It can be that your unit is tired, and the switch just forces full pressure instantly. Something to consider. nipper Link to comment Share on other sites More sharing options...
Gloyale Posted January 8, 2007 Share Posted January 8, 2007 It can be that your unit is tired, and the switch just forces full pressure instantly. Something to consider. nipper I though that may be the case. but at anyrate it does help, since alot of these systems are getting quite old. To your point i also have a 93 legacy automatic with no modifications at all. It transfers really well. Seemlessly almost. I can take off from a stop in deep snow or stab the gas in a turn and I get almost immediate push from the rear. That Tranny has 290,000 miles!!!! I think it may just be that the really early systems(like my GL) where not as well managed by the TCU. ''Something'' (which I did not figure out yet) sens information (volts) to the selenoid C that controls the hydraulic pressure applied on clutches. The TCU processes info from the throttle sensor and an ignition pulse from the coil. Along with info from the Speed sensors and ATF temp sensor. Later systems, 95+ may use more info but I know for myself so I won't say. The signal to the Duty solenoid C is then determined and sent from the TCU. note: if your ATF temp light is on for any reason while driving, you will get <5% torque transfer(unless you use the switch) This is to protect the system from High ATF temp. But it's annoying if you're light is shorted and always on(mine was shorted and always stayed on, even right after a cold start) or if the sensor fails(you have to pull the trans oil pan to replace). Link to comment Share on other sites More sharing options...
nipper Posted January 8, 2007 Share Posted January 8, 2007 .note: if your ATF temp light is on for any reason while driving, you will get <5% torque transfer(unless you use the switch) This is to protect the system from High ATF temp. But it's annoying if you're light is shorted and always on(mine was shorted and always stayed on, even right after a cold start) or if the sensor fails(you have to pull the trans oil pan to replace). Has anyone ever overheated thier tranny to get the light come on? I am just curious nipper Link to comment Share on other sites More sharing options...
Gloyale Posted January 9, 2007 Share Posted January 9, 2007 Has anyone ever overheated thier tranny to get the light come on? I am just curious nipper I don't know but I've had mine short and stay on. the wires for it are shielded. Car had an Engine fire before I bought it(failed wastegate). The fire melted the shielding through the insulation on the inner wires and shorted it to ground. AWD wouldn't work right, and it stayed in the "power" shifting mode so it was revving way high before shifting and shifting abruptly. Both conditions are "failsafes" when the temp light goes on. Link to comment Share on other sites More sharing options...
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