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Old 08-02-2008, 09:54 PM   #1
Primergy
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Member#: 167826
Join Date: Dec 2007
Location: ~Seattle
Vehicle:
1995 Legacy L
Green

Default 95Legacy: AWD<->FWD switchable on AWDs?

Hi,
a friend (mechanic, non-Subaru) mentioned something.
Is there a way to modify a 95 Legacy to switch between AWD and FWD?
The car was also available as a 2WD version and older Legacys can switch by default.

Originally there could be a way to switch, just to run them on a 2WD dyno?!?
My car does not need a dyno run, but for longer hwy-runs in the summer etc. it should save a bit of gas.
Also, just to individualize the car a bit I guess, since I am not into big HP tuning...

I am a hobby mechanic myself, my experience with Subaru cars is limited.
But since I drive one... I sure want to learn!
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Old 08-02-2008, 10:24 PM   #2
Frogsthatmoo
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Member#: 153374
Join Date: Jul 2007
Chapter/Region: South East
Location: Ocala, FL
Vehicle:
2001 Outback Wagon
White

Default

There's a fuse that will let you do that, but it's only for emergencies when you have to put a spare tire on the car. AWD cars do not like mismatched tires so you have to put the donut tire on the back and then make the car FWD. It's ok to drive short distances at lower speeds but it's bad for the differentials because everything is still physically connected.
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Old 08-02-2008, 10:51 PM   #3
Jonathan
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Join Date: Feb 2001
Chapter/Region: NESIC
Location: Natick, MA USA
Vehicle:
1999 Legacy GT Ltd
Quick Silver Metallic

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Quote:
Originally Posted by Frogsthatmoo View Post
There's a fuse that will let you do that, but it's only for emergencies when you have to put a spare tire on the car. AWD cars do not like mismatched tires so you have to put the donut tire on the back and then make the car FWD. It's ok to drive short distances at lower speeds but it's bad for the differentials because everything is still physically connected.
This is the FWD enable fuse.

It is ONLY for use with the automatics (4EAT) not the 5 speed.

As the AWD mechanism on the Automatics is an electronically controlled series of clutch packs, I can't see how running your car (if it is indeed an automatic) in FWD mode will harm anything.

Although if there is anything in the owners manual that says that its only for temporary short term use, then maybe its not such a good idea.

I don't see your gaining a whole lot with AWD disabled, as the automatics generally run with a ~ 90% bias on the front wheels anyways, but I would be interested to learn from your experiences.
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Old 08-02-2008, 11:06 PM   #4
Frogsthatmoo
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2001 Outback Wagon
White

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Quote:
Originally Posted by Jonathan View Post
This is the FWD enable fuse.

It is ONLY for use with the automatics (4EAT) not the 5 speed.

As the AWD mechanism on the Automatics is an electronically controlled series of clutch packs, I can't see how running your car (if it is indeed an automatic) in FWD mode will harm anything.

Although if there is anything in the owners manual that says that its only for temporary short term use, then maybe its not such a good idea.

I don't see your gaining a whole lot with AWD disabled, as the automatics generally run with a ~ 90% bias on the front wheels anyways, but I would be interested to learn from your experiences.

Well, drive around for a year in FWD mode and tell me how your transmission is doing. Then I will believe you that it's ok for the car.
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Old 08-02-2008, 11:57 PM   #5
Primergy
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Join Date: Dec 2007
Location: ~Seattle
Vehicle:
1995 Legacy L
Green

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Sorry, forgot to mention.
My car is a manual!

How did the on-the-fly 4WD/2WD selector on a Loyale for example work?
Here is an example from eBay with some pictures...

So far, thanks for all the infos!
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Old 08-03-2008, 12:22 AM   #6
Frogsthatmoo
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Location: Ocala, FL
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2001 Outback Wagon
White

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Yeah, you don't have the ability then, sorry.

What an interesting place for a spare tire!
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Old 08-03-2008, 01:12 AM   #7
Jonathan
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Join Date: Feb 2001
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Location: Natick, MA USA
Vehicle:
1999 Legacy GT Ltd
Quick Silver Metallic

Default

Quote:
Originally Posted by Primergy View Post
Sorry, forgot to mention.
My car is a manual!

How did the on-the-fly 4WD/2WD selector on a Loyale for example work?
Here is an example from eBay with some pictures...

So far, thanks for all the infos!
Yeah, the manuals have a "Viscous coupling". Basically The manual AWD system is similar in concept to a "torque converter" coupling on an automatic transmission, except that instead of Automatic Transmission fluid the AWD coupling uses a synthetic goo like substance that the hotter it gets, the thicker it gets... so when the front and rear axles are turning at roughly the same speed this "synthetic goo" has a consistency of honey, but if one axle is spinning and the other has traction (and is just sitting still), the fluid in the fluid coupling thickens up fairly quickly and both axles start to turn at the same speed. This setup works well as there is enough of an allowance for variations in front and rear axle rotational speed such as very minor differences in tyre sizes, and the differing front and rear rotational speeds when corning.

While I am not directly familiar with the part time 4WD setup on a Subaru Loyal, I imagine it is pretty much like any other crude part time four wheel drive system, where some form of a "transfer case" is utilized... which typically concist of either a gear or a chain coupling, and special gear driven synchronizers that only let you engage 4WD (I.E. "Shift on the fly") when both front and rear axles are turning at EXACTLY the same speed... Once one pair of wheels starts spinning, or if you are not driving straight ahead and the axles are spinning at differing speeds the sychronizers wont allow you to engage 4WD.

While these 4WD systems are fairly efficient in terms of power transfer, they do not allow for any variances in front and rear axle rotation, and thus really don't work especially well at normal road speeds on hard surface pavement, thus they are called "part-time Four Wheel Drive" systems Vs. "All Wheel Drive" systems that are designed to allow some percentage of "slippage" between front and rear axles and can therefore work well on paved roads.

EDIT: I actually took the time to look at the E-Bay Auction for the Loyal Station wagon. This car utilizes a 4WD push button switch located on the gear shift handle in place of an old style "transfer case" shift lever. When you depress the 4WD button the system will attempt to engage the 4WD gear or chain driven coupling, only if both axles are turning at the same speed, otherwise you are stuck in FWD.

Last edited by Jonathan; 08-03-2008 at 01:22 AM.
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Old 08-03-2008, 01:18 PM   #8
ballitch
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Location: salem, OR
Vehicle:
98 cam'd EJ251
Wrx Tranny,slowr than ish

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I have an 86 GL wagon with the lever type 4wd. It is a direct mechanical connection when you engage the lever. You can even be driving, and put the car in 4wd. This whole system is housed internally inside the transmission.

As far as the push button, the tranny is almost the same, except for that little button activates a solenoid that moves the 4wd selector. IIRC.


You can drive with 4wd engaged on the road, but I only do it when it is wet, or on gravel. If you try it in the dry, you will notice a very nice tranny bind in some instances. It can get very bad, almost to the point where you cant move the 4wd lever out of 4wd.


~Josh~
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