AWD to 2WD harmfull for the transmission?

cgilb wrote: --- snip ---

If you run an AWD vehicle as a 2WD vehicle, the fuel consumption should not be affected.

This is because the friction losses resulting from the two additional diffs and the transfer case churning oil remains the same; unless you actually remove these units.

I suggest you reveiw your method of obtaining mpg figures.

Uh, Terry, I'd suggest he take his car to a mechanic that knows more about Subarus. Maybe his figures are right.... And, since you're right that this

*shouldn't* make a difference in gas mileage, perhaps whatever was causing the transmission shake also caused poor gas mileage?

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There's got to be something wrong. My 1995 2.5L automatic Legacy wagon gets 10l/100km in the city and as little as 8.7 on the open road.

Even towing a 10m long glider trailer it's only about 11.

The FWD mode via that fuse is intended for temporary, emergency use only such as when the car has to be towed with the wheels on the ground. It is not meant to be left that way for normal driving. From your description it sounds like there is a problem with one of the differentials. You need to get this repaired ASAP rather than ignore it by driving around with the fuse inserted. You also need to find a different shop that knows more about Subarus as your present mechanic apparently doesn't.

cgilb wrote:

In fact, it was a mechanic specialized in automatic transmission who did the change in the fuse box. The Subaru dealer had nothing to say about that and the only suggestion the mechanic had was to open the transmission and replace some plates. A second opinion from a specialized transmission was that there was nothing wrong with my transmission. The third one I saw suggested the change to see if it would solve my transmission binding on turns and it did. The increased gas milage is more a finding after the fuse was inserted.

For the first 2 years I own this Subaru Outback wagon I have registered the milage for every tank of gas. In the summer, I averaged 11.5 liters to 1 gallon imp. In the winter, this figure rose to 12.5-13 liters to 1gallon imp. So it was a surprise to me to realize that inserting this fuse to remove the AWD has reduced my gas consumption. To reduce the gas milage was not what I was looking for!!

Everytime I fill the gas tank I always set the odometer to zero so that I can check. I have been doing this because the needle gage is at empty when I reach 375 km. When I reach 500km more or less, I stop for refueling.

Thank you for giving me your opinion.

Claude

I understand very well. My concern with the Subaru mechanic is that on a previous Subaru Wagon 1985, the mechanic changed my radiator, the thermostat the sensor on the motor for a problem of overheating that was not solved, to finally teel me that it was the gage that was faulty. Later,I had to pay for a cracked head that was causing the overheating. You may now understand why I am sceptic as to what they advise me to do and it is the reason why I seach for a second and third opinion. What would you do if you had to deal with my problem? Go to a Subaru Dealer....again????? Thanks for your advice.

Claude

I do the same.

Around town I get pretty much exactly 100 km from each quarter tank, then another 60 or 70 before the light comes on, then another 60 or 70 before it's empty.

On the open road each quarter tank lasts 110 - 120 km. I've gotten close to 600 km a couple of times, cruising at 110 km/h (70 mph).

< < I own an automatic AWD Outback Wagon 1997. I had a problem of "vibrating transmission ", I went to a specialist and he disengaged the AWD fonction by inserting à 15amp. fuse in a small box under the hood where it is written AWD. As soon as he did it, we drove the car and the problem was solved and the vibration disappeared but not repaired. > >

Sounds like the centre diff would be a good place to look first. At least by removing the fuse he's given you temporary respite and probably eliminated the trans and the front end as a cause all in one hit. Cool. Also sounds like he's prepared to throw brain cells at a problem in the first instance rather than large customer invoices - always a good sign IME. Agree 2WD shouldn't use less fuel than 4WD in this scenario but no-one seems to have told AWD Subarus the basic physics underlying this principle - so they ignore it! Cheers

It sounds like your electronically controlled clutch pack (no center diffs on this vehicle) needs to be replaced. This seems to be a common problem.

Claude, tires with slightly different diameters due to wear, etc. could be causing your chattering/binding problem. -Danny

Thanks Danny,

I'll check and let you know. I was also told that the circumference of the tire had to be check, which I didn't do...??? Claude

Well sure, a different diameter would translate to a different circumference.

There is a fairly narrow allowable tolerance, but I don't know what the spec figure is.

Yes, it's ¼ inch. Thank you for your advice.

spec figure is.

>

I would debate that due to the fact that the engine is running and activating the pumps for the transmittion fluid. On most cars the fluid is run through the radiator for cooling/warming so there is a pump inline with the system.

Brian

Basically - just about any difference in wear between pairs of tyres may put you over the 1/4". IME it doesn't have drastic short term effects, (I've had to run completely different tyres front to back on more than one occasion), whereas centre diff &/or centre clutch pack problems can stuff things up quite quickly (like no apparent problem to 'failure to proceed' in less than 1000km with ours!) Cheers