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Try searching on FWD fuse on this forum -- you'll find LOTS of discussion on the topic. I personally can tell you that I ran for over a year with a fuse in the FWD socket of my Outback with no ill effects, but I am a stickler for changing AT fluid and such, so the duty solenoid that the fuse turns ON full time probably never got too hot in my case.

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BUT - Don't think that this will save you any gas; it won't. Gas mileage doesn't change much, probably because all that hardware on the rear end is still turning, even if it isn't actively driven by the tranny. I saw no change in average mpg with the fuse in, vs. with the fuse out.

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this saves zero gas. :horse:

the only way you save gas is by removing the drieshaft and rear differential, and even then it isnt even 1 mpg. Also these cars were deisgned to be AWD, not FWD with AWD added as an afterthought. Even with the awd disconnecetd, all the awd parts are still moving and being driven by the car.

Driving with the dut c solenoid in the car all the time, your better off selling the car and buying something else then. The awd works all the time, and is quite noticible, especially in the rain, when it is deactivated. Eventually the solenoid will burn out, and the 200-800 repair will totally wipe out any gas savings, in fact you will never make that money back.

 

nipper

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I ran my 91 Legacy in Fwd for a week and like the others, my mileage was exactly the same (it's very consistent).

 

What I find odd is when I drive my Grand Cherokee in 2 wheel drive instead of full time 4 wheel drive, it gets significantly better mileage. All the parts on the Grand are still spinning as well, it only disconnects at the transfer case not the hubs.

 

The only reason I can think of is the Subaru is only sending 10% to the rear wheel most of the time. Thus it's already as lightly loaded as you're going to get in normal driving.

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I ran my 91 Legacy in Fwd for a week and like the others, my mileage was exactly the same (it's very consistent).

 

What I find odd is when I drive my Grand Cherokee in 2 wheel drive instead of full time 4 wheel drive, it gets significantly better mileage. All the parts on the Grand are still spinning as well, it only disconnects at the transfer case not the hubs.

 

The only reason I can think of is the Subaru is only sending 10% to the rear wheel most of the time. Thus it's already as lightly loaded as you're going to get in normal driving.

 

the cherokee has a transfer case with many more parts inside it. These parts creat alot of drag. There are internal parts that stop spiing whn you are in 2wd, hence the gain. Also the case is desighned to have all the internal parts stop spinning for better gas mileage.

 

in the subaru its not so much the 10%, since thats not totally true. It consantly varies between 10%-50% in all conditions, and in the manual its 0% or 50%. Just in the automatic the parts are along the driveline so there is no mass to change direction. in the manaul you cant really do anything about it, as there are a lot of parts with forces changing direction, but since they are all built into the tranny, you cant disconnect them.

 

nipper

 

nipper

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What I find odd is when I drive my Grand Cherokee in 2 wheel drive instead of full time 4 wheel drive, it gets significantly better mileage. All the parts on the Grand are still spinning as well, it only disconnects at the transfer case not the hubs..

 

i 'm not sure about the grand cherokee but my dads comanche has a vac motor on the back of the front axle to dissconnect the front axle. his drive shaft doesn't spin. some of the cherokee's are like that to. but the grand cherokee might be different.

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i 'm not sure about the grand cherokee but my dads comanche has a vac motor on the back of the front axle to dissconnect the front axle. his drive shaft doesn't spin. some of the cherokee's are like that to. but the grand cherokee might be different.

 

That's "CommandTrac", my brothers YJ has that too. ( Actually it did until he built a mechanical cable release to replace it, the vac motor is very durable). Some base Grand Cherokees came with this system but not many.

 

Ours has "SelecTrac". Both axle shafts spin all the time as does the front drive shaft. It's only disconnects at the transfer case. It also has a lockable centre diff that allows full time 4 wheel drive which the base system doesn't have.

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FWD mode is for maintenance, not for daily driving! You'll burn the solenoid that way.

 

yes and no. Some here have burned then out in two months, some have gone on years. Just depends upon your luck.

 

nipper

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The Grand Cherokee also has Auto locking front hubs, that engage and disengage when you shift into 4wd. So the front wheels spin free when not engaged, all 4wd's are the same way. Some autolock some lock manually, (you get out and turn the lock on the hub) But unless they are awd, the hubs disengage when not in 4wd to save wear and tear and save gas.

 

That's why the difference in mileage is so dramatic.

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