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OK to drive with "FWD" fuse in. How long ??


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Posted previously about my clutch pack problems.

 

Since the car drives OK with the FWD fuse in place....in 2wd mode...I'm wondiering how long can I drive that way.

 

A few miles?? Indefinitiely??

 

I read on another Subaru board that it wasn't OK to drive in FWD for a long time...it would cause some damage??? True or False?

 

Warren C

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You shouldn't drive with the FWD fuse in for a long time. Here's the reason. The duty c solenoid is designed to get a pulsed on/off signal voltage. When you put in the fuse, you send 12v constant to the solenoid so it opens all the way. That constant signal is going to wear the solenoid out a lot sooner.

 

How much sooner....I don't know.

 

Regarding the rear diff comment. I wouldn't personally recommend that either. You'll run into issues.

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What kind of issues? My duty c solenoid is having occassional hiccups, and I was thinking that rather than replace it should things take a turn for the worst I would simply disconnect/remove the driveshaft until I have more time/money. Since the rear CV axles will be in place, the differential will be kept in motion, so siezing up shouldn't be a factor.

 

Also, why would I need to keep the fuse in place to run without the driveshaft attached?

 

Regarding the rear diff comment. I wouldn't personally recommend that either. You'll run into issues.

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What kind of issues?

 

none, i've done it before. drive away. definitley zero effect on your rear diff, it won't be seeing any power so that's not an issue. if you're constantly powering on the duty solenoid C you may cause issue, but mine never failed and i've done this before. i have a switch in place to control my duty solenoid C so it's gets lots of use. no issue to date, this is on the first gen of 4EAT transmissions, the newer ones do seem to have more issues than the older ones, but i would expect no ill effect based on my experience. i've done this to auto and manual trans and driven lots of miles, highway miles, 1600 miles round trip back and forth between maryland and georgia....no problems.

 

Also, why would I need to keep the fuse in place to run without the driveshaft attached?
first - the driveshaft slides into the transmission so yo'ull definitely need to keep the end of the driveshaft in there to prevent fluid from pouring out the rear extension housing. the driveshaft slides through a seal in the rear of the transmission. so you have to remove the rear half of the driveshaft (they are typically in two "pieces"). if you remove the driveshaft and try to drive, the rear output shaft of the trans will spin....but it's not connected to anything and fronts won't get any power. it's because of the way the trans works. try it, but you won't go anywhere.
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it doesn't save gas mileage.

 

that's not the only reason to do it - failing transmission, broken axle shaft, bad drive shaft ujoints and failing rear differential are other possibilities.....except for failing transmission i've been presented with all of those issues in subaru's and used the driveshaft removal method for anywhere from a day to a year and a half with no issues.

 

i've done it enough to know you are exactly right too, no gas mileage difference!

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Regarding the rear diff comment. I wouldn't personally recommend that either. You'll run into issues.

 

there's no possibility of rear diff issues from just removing the driveshaft, if anything it'll make it last longer, less power (none from the trans) going through it so less wear theoretically though that would never show itself in practical terms.

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Problem is....I've got a serious problem with my clutch pack that only (right now) goes away when the FWD fuse is in place.

 

Problem started with the usual torque bind symptoms. Inserting the FWD fuse made no difference. Swapping the tranny control unit made no difference. Suspected the Duty C. Removed the tranny tail housing and checked the Duty C which seemed to be OK...., clutch plates seemed to be free and moving OK against each other.....

 

After the tail housing was re-installed....I got a new problem ....a sound like "marbles" in the tail housing and a clicking on each revolution....worse in turns......

 

Frustrated....I swapped in another complete used 4EAT tranny....on test drive I get the EXACT same sounds......marbles and clicking in the tail housing ....that goes away when the FWD fuse is inserted...so now the Duty C is good...but still BIG PROBLEMS.

 

So I could disconnect the rear of the drivshaft but inserting the FWD fuse will likely give me back my marbles and clicking sounds.

 

Need some serious tecnical help here....someone who really knows how the clutch pack works.

 

Warren

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Thank Gary, I appreciate the info. One followup question though. If I remove the rear half of the driveshaft, is there concern over leaving the remaining portion free spinning? If so, is that why there was the mention of using the fuse simultaneously? Because It would seem that it shouldn't matter then if the fuse is in provided there is no problem leaving the front portion of the driveshaft spinning (which I don't see why there should be).

 

Not that I want to be without AWD, but if worse comes to worst...

 

p.s. - this actually should improve gas mileage slightly due to reduced friction on the rear diff I believe, unlike just using the fuse

 

 

there's no possibility of rear diff issues from just removing the driveshaft, if anything it'll make it last longer, less power (none from the trans) going through it so less wear theoretically though that would never show itself in practical terms.
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p.s. - this actually should improve gas mileage slightly due to reduced friction on the rear diff I believe, unlike just using the fuse

definitley not the case. done it on a number of subaru's, no change. doing it right now actually. no difference at all, not even a teeny bit.

i've done it enough to know you are exactly right too, no gas mileage difference!

 

If I remove the rear half of the driveshaft, is there concern over leaving the remaining portion free spinning?
no, i already explained this earlier in the thread. again - done it before.
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Problem is....I've got a serious problem with my clutch pack that only (right now) goes away when the FWD fuse is in place.

 

Problem started with the usual torque bind symptoms. Inserting the FWD fuse made no difference. Swapping the tranny control unit made no difference. Suspected the Duty C. Removed the tranny tail housing and checked the Duty C which seemed to be OK...., clutch plates seemed to be free and moving OK against each other.....

 

After the tail housing was re-installed....I got a new problem ....a sound like "marbles" in the tail housing and a clicking on each revolution....worse in turns......

 

Frustrated....I swapped in another complete used 4EAT tranny....on test drive I get the EXACT same sounds......marbles and clicking in the tail housing ....that goes away when the FWD fuse is inserted...so now the Duty C is good...but still BIG PROBLEMS.

 

So I could disconnect the rear of the drivshaft but inserting the FWD fuse will likely give me back my marbles and clicking sounds.

 

Need some serious tecnical help here....someone who really knows how the clutch pack works.

 

Warren

 

I didn't understand, you did disconnect the drive shaft and still got the problem?

If not, did you look into the rear diff?

It can fail too, but usually with a catastrophic effect.

 

 

BTW, FWD fuse gives no MPG benefits. Once I did 1000 miles of hwy with and without and didn't see a difference.

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there's no possibility of rear diff issues from just removing the driveshaft, if anything it'll make it last longer, less power (none from the trans) going through it so less wear theoretically though that would never show itself in practical terms.

 

Gary,

 

I'm not concerned with the rear diff.

 

The reasons you mention in your thread explaining what you did are the reasons I'm referring to.

 

Removing the rear half of the driveline really probably isn't the best thing to be doing. It may have worked fine for you, but it's something I can't recommend.

 

Maybe I'm being too overly cautious, but that's just my take on it.

 

BTW, the 90 n/a legacies & 91 turbo legacy had one piece CV-joint style driveline, and can not be separated.

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that's not the only reason to do it -

i've done it enough to know you are exactly right too, no gas mileage difference!

 

i didn't say it was the only reason. a lot of people think that turning it into a fwd car will turn it into a honda. they forget to take into account that you're still turning the rear drive components and that takes power.

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It;s a 96 OBW...

 

I think I may have figured out....

 

I think some part of the driveshaft....a u-joint or ??? is hitting part of the exhaust heat shield.

 

Had a tranny in the back to deliver today and it was hitting a lot.....more when decelerating or going over bumps.

 

Warren C.

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Huh?

 

That doesnt make sense with the original complaint, thet two trannies had torque bind in a row. That would only cause a noise, not an operational failure. Also if it was hitting it, since the driveshaft is always turning, you would have the noise all the time

 

 

 

nipper

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Huh?

 

That doesnt make sense with the original complaint, thet two trannies had torque bind in a row.

 

 

The think after the tranny's were replaced, the torque binding was gone....it was just the clicking, rattling sound that was the issue.

 

I have to put the FWD fuse back in to test the binding again. The clicking, clanging, rattling sound is worse with it in.

 

Warren

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