There's a fuse slot under the hood of my '95 Legacy that the owner's manual tells me is for switching to FWD for "testing purposes". I am curious about setting the car to FWD for a while to see how it effects the handling, acceleration and especially the MPG. However, I'm concerned about whether doing so may harm the AT, the transfer case, or the center diff. Secondary to this, if I were to run a switch to the dash for this circuit could I switch back and forth between AWD and FWD "on the fly" or would I need to come to a complete stop to switch it over? TIA.
it wont hurt anything, however you wont see that much of an improvment, and yes it is possible to run a switch, a tech here at morries did it on his own car when the driveshaft hanger bearing was going out, so it wouldnt flop around.
In the owners manual it says to not drive more than 10 miles with the fuse in there. I am not sure why that is. I know how the system works. putting the fuse in completes a circuit which disengages the clutch in the center diff. I am not sure if they clutch can fully disengage and this is why they dont recommend driving like that. The clutch in the center diff is actuated by a soleniod which is controlled by voltages. The TCU can alter the voltage as you are driving, so under acel you get close to a 50/50 distribution and cruising on the highway it goes more towards 90/10. you can wire the fuse into a switch so that you can engage/disengage FWD mode at will. people have also wired this switch to the EBrake (or ebrake light) so that you diengage the clutch when the ebrake is pulled, this has the potential to reduce any damage done by ebraking. however I am not totally sold on this. if you are hard on the gas and drop the ebrake the clutch will engage. I am not sure how this shock will affect the AWD sytem long term. another cool idea i had, was to wire a potentiometer the soleniod so that you can control the level of engagement yourself (4eat/poor mans dccd?) not sure about the effectiveness or long term hazards of this though.
well...it's not exactly good for the trans. but I highly doubt you'll notice any extremely premature malfunction. you will not notice almost any increase in mileage. as the reason that the AWD hurts mileage so much, is all the extra moving parts. just disengaging the trans side isn't going to do anything, because everything stays spinning. now, if you had some sort of hub lockouts on the back....yea....you'd probably notice something. as for handling/acceleration differences. expect more understeer, less traction, etc. possible? yes worth it? not really
Thanks guys. I had some errands to run last night and switched it over to FWD just to see what dry-pavement differences I could feel. It definitely felt a lot peppier off the line but I didn't much care for the torque-steer and tire spin at painted crosswalks. Off-throttle the steering felt much more responsive but on-throttle it felt sluggish and like it was fighting the torque. My primary reason for wanting to try this was to improve MPG but opinions seem pretty much unanimous in that it wouldn't help. I pulled the fuse back out this morning.
