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Guest Message by DevFuse

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AWD Switch, very cool

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32 replies to this topic

#26 Guest_Legacy777_*

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Posted 04 November 2002 - 09:38 AM

It's only available on automatics because the way subaru's automatic works is that it uses an extension housing with clutch packs to power the rear driveshaft. These clutch packs are driven with tranny fluid.

The tranny fluid pressure is limited with a solenoid, that is controlled by the ECU. It is an electro-mechanical-fluid based system. ECU controls mechanical solenoid, which in turn limits fluid pressure.

By changing the electrical signal, you can manipulate torque split to the rear.

In manual transmission cars, the torque split is controlled by a sealed center viscious differential. It is a fluid-mechanical system. The diff has plates that reside in this fluid. When a wheel in the front or rear spins, the drive shaft spins faster. This causes the plates in the fluid to spin faster then the other side. This creates heat and essentially locks up the other plates to the same speed as the faster spinning ones.

That's an overly simplified description. But there's no way to change how that sealed unit works.

wjmgl10: For automatics I am pretty sure you don't want any of the wheels on the ground. The reason is that the engine needs to be running to lubricate the gears & everything on the tranny. If you have componants moving without lubrication......you cause problems.

For the manual trannies. The gears are self-lubricating. As they turn, they pickup gear oil to lubricate themselves. So you can technically tow an AWD manual trans. car with all four wheels on the ground. If I were having my car towed....I'd probably want it on a flat bed though....

#27 Guest_SSJCody_*

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Posted 04 November 2002 - 05:51 PM

So is the torque split always the same in manuals?

#28 Guest_wjmgl10_*

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Posted 04 November 2002 - 06:40 PM

50/50 manual. on all of them.

thanks for clearing that up, Leagcy777.

#29 Guest_Legacy777_*

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Posted 05 November 2002 - 08:33 AM


When we are talking about torque split. I am mainly talking about under normal driving conditions. Like when you're driving down the highway and there is no tire slippage going on. For manual trans cars, under normal driving conditions, torque split is 50/50.

Once slip occurs the torque split can pretty much be an infinate amount of combinations.

#30 Guest_SSJCody_*

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Posted 05 November 2002 - 06:31 PM

Ok, thanks for clearing that up.

#31 Guest_Nic LT_*

Guest_Nic LT_*
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Posted 06 November 2002 - 06:22 PM

Hi, i'm new on this board. I just got an 1993 Impreza AWD auto, that will receive a 5spd 2001 2.5RS powertrain, brake and suspension this winter. Snow is already falling here (quebec city) and I want to know how to stop the Duty C solenoid action in order to get a 50/50 torque split. I want to try this in order to make my controled sliding a bit more predictable, and more like a manual tranny. Thank you very much !

#32 Guest_Legacy777_*

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Posted 06 November 2002 - 09:14 PM

break the signal between the duty c solenoid & ECU.

i.e. find the wire from the duty c solenoid that goes to the ECU, splice a toggle switch inline.......and flip it off for 50/50 split

#33 Guest_rallitek_*

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Posted 08 November 2002 - 11:15 PM

Hey guys , the fwd override in your auto trans just holds the pressure relief solenoid in the transmission open. the pressure we are talking about squeezes clutches together when the computer senses wheel spin , otherwise it is already dis-engaged.all the machinery for AWD is still turning and causing the friction that robs fuel mileage. the override switch or adding the fuse will not affect fuel mileage. , cool idea though.

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