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FWD fuse and space-saver spare


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Ok, I'm coming off of panic mode right now wondering what I may have done to my car yesterday. I headed from Ontario to NC and after a long day in Baltimore traffice I crossed the VA/NC border around 9pm and when I went for gas saw a scary-low right front tire.

 

I knew there was no way to finish the last 45 miles on it, so out comes the wimpy donut spare. Swap the two and after cursing myself for not checking the spare pressure before leaving, I head down the road at 45 mph for about 10 miles to find a gas station with compressed air.

 

After filling the space saver spare to required 60psi (I finished the trip but not before the CEL came on).

 

This morning I woke up and realized I'd just driven 50 miles on the spacesaver spare (in the right front) without having put in the FWD fuse. So I pull the radio fuse, plug it into the FWD slot and head to the tire store. One new tire for now (the rest will get done soon, after next payday).

 

So my questions are: How bad could I have hosed things by driving this far w/o dropping into FWD with the fuse? What should I do now to be sure nothing gets worse (i.e. change/check fluids etc)? How urgent is the replacement of the other four tires? The oddball is well-matched tread, same size, different brand. I'm still running FWD should I do this until I replace the rest of the tires, and would it be good or bad (or neither) to move the odd tire to the back vs. the front?

 

Finally: The CEL is a P0420, it's been cleared and didn't come back on today yet (knock on wood). Could this be at all related (from slow highway speeds, with several back to back stops) or just bad luck and part of an epic journey home?

 

I don't know when the O2 sensor was last changed (I bought this car at 96k and it's now at 107k, new belts and h2o pump at 104k ... $$$)

 

Sorry for the long post, I suspect this is still an unresolved conflict (about the robustness of the AWD system) but any tips and or experience are welcomed.

 

Thanks,

Andy

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I would put the fuse in and put the odd tire in the rear. GET 3 MORE ASAP!

 

BTW, the p420 code is for a failed cat. converter I believe. Totally unrelated, just dumb luck :) I guess it probably had to do with the heat generated from your drive from Ontario to NC.

 

good luck!

 

Kevin

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First of all, usually only the clutch pack in the automatic transmission is damaged when the car is driven with unmatched tires. It is not a cheap repair, but it isn't a transmission overhall or replacement either. When you have four matching tires put the car back into AWD and check for binding. Take a very sharp turn at a low speed, like heading into a parking space. If the car shudders, you probably have a problem. Keep the car in FWD until you have replaced the tires. You should get off the compact spare ASAP. Besides, riding around without a spare tire is an open invitation to get thoroughly hosed by some tow truck operator. It is not safe to operate the car on a compact spare. It is designed an emergency stop gap measure only. It may not be necessary, but wouldn't hurt anything to have the AT fluid changed. It depends on the condition of the clutch pack before the incident, and how badly the tires were mismatched. But I would not be overly suprised if you got lucky, and the clutch pack is still functional. You did however, probably put a some amount of abnormal wear on the clutch pack during that 50 mile ride.

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Well, Dude, you seem to know yer stuph.

 

I've got a Dummy of The Year Trick which I pulled a week ago.

'91 Legacy auto/4wd

I towed it about 140 miles with its back tires on a tow dolly (bad rear wheel bearing) and the front tires on the ground, trans in N, of course!

Top speed 50 mph, yet the trip took nearly 4 hours.

Now, I have only low gear forward no matter where the selector lever is located, no reverse, and when I decelerate, the tranny does not hold the car back.

Got any suggestions as to what I may have damaged/screwed up (or should check) with my Dumb Human Trick? (I knew better, and figured that low speeds wouldn't hurt.)

Thanks,

George

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Everybody has a bad day, and even a Subaru is still just a thing. I am not a AT expert. Every incident that I am aware of where an AT has been towed has resulted in major damage to the transmission. A number of posters have reported serious tramsmission damage after towing their AT Subaru only fifty feet. Exactly what breaks inside, I don't know. Everyone in this situation has reported that a tranny rebuild or replacement was required. It's probably worth a call to the local tranny shop for some free advise. Sorry.

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Alright, I've exhaled. At this point I have a new tire (I was only on the space-saver spare for the 45 miles home). It's been in FWD ever since I realized what I'd done. For now I'll throw the odd tire onto the back and leave the fuse in. For now I'm driving my jeep around so I can leave the sube until it's shoes match again. I'll keep my fingers crossed about it. Even at the end of the trip (with the fuse out, and the spare on) I didn't notice any binding during street-corner drive to my house... but I'll certainly double check it for binding.

 

On another note, why doesn't subaru put large orange letters on the space-saver spare that mention the fuse in the FWD slot? It seems like an easy way to prevent stressed drivers from absent-mindedly hosing their clutch pack. Even the note in the manual is just a (somewhat hidden) instruction step, not a !WARNING! like many of their other comments about how to prevent damage to the vehicle. Guess I'll never forget it again... but still, such a well-designed system deserves to be protected from road-weary idiots ;-)

 

Thanks,

Andy

 

First of all, usually only the clutch pack in the automatic transmission is damaged when the car is driven with unmatched tires. It is not a cheap repair, but it isn't a transmission overhall or replacement either. When you have four matching tires put the car back into AWD and check for binding. Take a very sharp turn at a low speed, like heading into a parking space. If the car shudders, you probably have a problem. Keep the car in FWD until you have replaced the tires. You should get off the compact spare ASAP. Besides, riding around without a spare tire is an open invitation to get thoroughly hosed by some tow truck operator. It is not safe to operate the car on a compact spare. It is designed an emergency stop gap measure only. It may not be necessary, but wouldn't hurt anything to have the AT fluid changed. It depends on the condition of the clutch pack before the incident, and how badly the tires were mismatched. But I would not be overly suprised if you got lucky, and the clutch pack is still functional. You did however, probably put a some amount of abnormal wear on the clutch pack during that 50 mile ride.
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Just a small update on my situation. I've still got one new tire (I'll move it to the back today or tomorrow) and I'm running in FWD around town (~2m to work so not much during the week).

 

Just to satisfy my curiousity, and for some peace of mind, I came to work early for the empty parking lot and pulled the fuse. Did some slow straight driving, a couple turns, then sharper turns, and then faster sharper turns. All seems well and no signs or sounds of binding. I put the FWD fuse back in just to avoid any damage from having one new tire with three older ones.

 

I'll probably accelerate the schedule for changing the AT fluid just to be on the safe side. I also plan on taking some orange paint and adding the letters F U S E to the spare tire's wheel just in case I'm weary enough to forget this next time a tire goes.

 

Thanks for the replies all and hopefully my experience is another demonstration that subaru AWD isn't the fragile system some may have us believe.

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