Any Risks when driving in FWD only?

[yarikoptic]

instead of 1000miles try to do 10 "8-figures" driving backwards

[The Dude]

Yes, now that you have four matching tires it is very unlikely that you will cause additional damage to the clutch pack. If you wish, you may drive the car a given distance in AWD and then drain and refill the AT. It may help, or you may just be out four quarts of AT fluid.

 

I certainly hope that you fix this problem with just a fluid change. BTW, a clutch pack replacement is not the end of the world. It is my understanding that the AT doesn't even have to be dropped for this repair.

[DooMeSuuby]

Thanks Dude.

 

Well... the mechanic started spouting "This is at least 10-15 hours, I have to take apart the whole AT, the clutch pack, I call it a "viscous coupler" it sits in the back of the transmission.... have to take the whole thing apart... I'm guessing this is around $2,500"

 

So, I wonder if I should post a new thread and ask if anyone has the scoop on replacing the clutch pack?

 

I am very thankful for your input.

 

David

 

 

 

Yes, now that you have four matching tires it is very unlikely that you will cause additional damage to the clutch pack. If you wish, you may drive the car a given distance in AWD and then drain and refill the AT. It may help, or you may just be out four quarts of AT fluid.

 

I certainly hope that you fix this problem with just a fluid change. BTW, a clutch pack replacement is not the end of the world. It is my understanding that the AT doesn't even have to be dropped for this repair.

[Al_SemC]

Just so you don't get confused, a clutch pack and a viscous coupler are two completely different things. They do the same thing, but not in the same way.

 

The AT's use a clutch pack. It's a series of wet-plate clutch plates and steel plates that get squeezed together by hydraulic pressure. This causes a variable amount of torque to be channeled from one side of the assembly to the other. The higher the pressure, the more torque is transferred. Think of it this way: take your hands and put them palm to palm like you were praying. If you rotate one while pressing lightly, nothing much happens. However, if you press harder, your other hand will twist a bit. If you press really hard, they will turn together with no slippage. The torque bind happens when the clutch pack gets crap in it or otherwise gets stuck and can't slip properly to adjust power when needed. When the front and back of the car need to go different speeds, like during turning, they can't. This causes the symptoms you're all too familiar with.

 

The MT models that don't have VTD ('01 and up, I think) use a viscous couple. It's not like a clutch pack; there's no physical contact between the the ends of it. Basically, there's a series of plates with slots in them inside it, suspended in a silicone based fluid. When both the front and the back of the car are turning at the same speed, the viscous couple really doesn't do anything. When they vary, like during slip, they plates inside turn at different rates. This drags on the fluid and makes it get hotter. When it gets hotter, it gets thicker. This causes the plates to drag harder and try to equalize in speed. It basically maintains a 50/50 F/R split all the time. It's a simpler system. It is, however, a bit slower to work. You can actually feel it kick in, unlike the AT ones which is done with sensors and a computer. i've never felt mine going. It just goes.

[sregor13]

How many miles in a row have you driven since the Fluid Change? Have you driven over 100 Miles on the interstate? I was just curious because everytime I think I have my binding issue is resolved it simply returns to haunt me. After months with no problems it will rear its ugly head.

 

As far as the Gas Mileage thing goes I am convinced mine gets better gas mileage in the FWD Mode. There is less resistance. But it is a small difference of about 15-20 Miles per tank. Could be wrong but I take a consistent route.

 

And on the Subject of Risks driving in FWD Mode- What scientific explaination is there to believe that it would damage anything? Isn't there someone out there can explain what could be damaged? Good Luck with you car I hope your problem is solved so I can have hope that mine is. But, until then I will be driving my Loyale in FWD Mode. Thanks, Gabe

[Al_SemC]

... And on the Subject of Risks driving in FWD Mode- What scientific explaination is there to believe that it would damage anything? Isn't there someone out there can explain what could be damaged? Good Luck with you car I hope your problem is solved so I can have hope that mine is. But, until then I will be driving my Loyale in FWD Mode. Thanks, Gabe

 

I hear that it can burn out the C solenoid that controls the transfer clutchpack. Putting in the fuse makes it run at full blast all the time; the higher the solenoid voltage, the lower the torque transfer. If they had designed it the other way around, i.e. so that the fuse grounds it out and that sets the transfer to zero, I don't think it'd be a problem.

[The Dude]

I hear that it can burn out the C solenoid that controls the transfer clutchpack. Putting in the fuse makes it run at full blast all the time; the higher the solenoid voltage, the lower the torque transfer. If they had designed it the other way around, i.e. so that the fuse grounds it out and that sets the transfer to zero, I don't think it'd be a problem.

 

In normal driving only 10% of the power is directed to the rear wheels. So, the C solenoid is 90% energized. Do you really think that just another 10% to the C solenoid is going to kill it? I don't.

[yarikoptic]

In normal driving only 10% of the power is directed to the rear wheels. So, the C solenoid is 90% energized. Do you really think that just another 10% to the C solenoid is going to kill it? I don't.

 

Besides that I don't recall anyone saying that it did have negative implications.

Myself, I was driving with it in for a few months... then fixed binding (new tires, oil, distance on highway, 8 figures in the reverse) - now it is fine working :-)

[sregor13]

It had been stated in this post ( I think) There have been several. Anyways it had been stated that the official word from SOA that there were negative implications. i.e. Only in low speeds and so on. cant quote verbatim..........but yea.

 

I liked Al Smokemcrack's idea better than just SOA says so. I still don't know what the Binding is caused by and why Figure 8's fix anything. Specualtion is great. I am just trying to understand the process. I was just skeptical that you can not drive with the Fuse in. Because I fully intend to put a switch on my Dash and use it like I would the old pushbutton 4WD Subarus.

 

Otherwise I read new tires new oil? What kind of oil would that be? Thanks

[Chef]

So after reading all written here and as much as I could find from other posts, it seems the overall consensus is that driving with the FWD fuse in place for extended periods will most likely not be problematic.

 

The main potential problems seem to then be:

 

1.) Possibly wearing out duty solenoid C

2.) More uneven tire wear, increasing the risk of torque bind

 

However:

 

1.) The solenoid is already mostly charged, and riding with it fully charged should not present too much more trouble.

 

2.) Rotating the tires more frequently should avoid torque bind issues

 

One other member noted he drove for over 20 000 miles with the fuse in place. He suffered from torque bind, but this was due to changing two tires for new ones and driving at high speeds for an extended period over a few days.

 

http://www.ultimatesubaru.org/forum/showpost.php?p=258232&postcount=18

 

So why ride in FWD?

 

Hypothetically the gas mileage should improve. At least one person noted no difference, and a couple a marginal difference (1 - 2 mpg). Given the lousy mileage, any improvement would be nice. Plus, it would be easy to install a switch inside that allowed one to switch to FWD from AWD at will, which would be damn cool.:cool: I'm interested in doing this, but only if it meant I would notice an improvement in mileage with little to no risk of damage to the vehicle.

 

Thoughts? Sorry for resurrecting this much ballyhooed topic.

 

Incidently, how difficult (and expensive) is it to reach duty solenoid C if it did need replacement?

[rude]

No.

 

I’ve driven over 20,000 miles in FWD mode, over 99% of the time. A few days the GF felt safer using the AWD on the highway, even though we’d get torque bind when turning at low speed. FYI you can shift in/out of AWD while cruising down the road if you install a switch.

 

 

 

Chef asked about tire wear and fuel mileage.

 

You will get more wear on the front tires in FWD mode (like any FWD car), but I’ve found more variation in tire manufacturers. I got 20k miles out of a pair of Dunlop Sport A2’s but since I had new half shafts put in (due to torn boots) and the toe was badly out of alignment for a few months. My wear numbers may not be very helpful. Just rotating would solve the problem.

 

 

 

I got about 24 MPG FWD compared to 22 MPG AWD, over a tank, each way, in the summer. In the interest of full disclosure the AWD was used in one direction of our trip because it was raining hard (some would argue an effect). Then again while in FWD it was warm and we had the AC on, and so on.

 

 

 

When finally having my torque bind issue addressed by a Subbie experienced mechanic he was not concerned about the extra wear on duty solenoid C. By keeping it in FWD, to avoid torque bind, I saved my clutch packs.

 

 

 

DooMeSuuby might be suffering from what my 95 Legacy LS had. Alias20035 knows quite a bit on the subject of mid 90’s torque bind and directs everybody to:

 

 

 

http://www.legacycentral.org/library/torquebind.htm

 

 

 

Hope this helps add some light,

 

Rude

[DooMeSuuby]

Hi Rude, and Alias20035,

 

Report from shudder-ville: (Or... '97 Legacy Torque Bind issue)

 

As first reported, my Torque Bind problem was very noticeable and scary.

 

I followed the directions from our good community here at USMB.

 

Installed 4 identical tires (Manufacturer, size) ($70.00 total, used)

Inflated all tires to 35 psi.

Complete flush/fill of ATF ($135.00)

I put her back in AWD.

I a 5-minute set of 8's in reverse.

 

I've been driving in AWD ever since. Allis well. EXCEPT....

 

sometimes, she f e e l s weak in the low-speed turns... like a barely detectable shudder occurs... and I have to wonder if its road surface.

 

IF the clutch packs were slightly damaged, I will be the real-time experiment to see what happens next.

IF the problem worsens, I will follow Alias20035's direction to change out the housing and install the steel plate.

 

Thanks for everything, and I hope my post today is helpful.

 

David

[Chef]

Thanks much rude. I appreciate the info from someone with first-hand experience.

 

Chef

 

 

No.

 

I’ve driven over 20,000 miles in FWD mode, over 99% of the time. A few days the GF felt safer using the AWD on the highway, even though we’d get torque bind when turning at low speed. FYI you can shift in/out of AWD while cruising down the road if you install a switch.

 

 

 

Chef asked about tire wear and fuel mileage.

 

You will get more wear on the front tires in FWD mode (like any FWD car), but I’ve found more variation in tire manufacturers. I got 20k miles out of a pair of Dunlop Sport A2’s but since I had new half shafts put in (due to torn boots) and the toe was badly out of alignment for a few months. My wear numbers may not be very helpful. Just rotating would solve the problem.

 

 

 

I got about 24 MPG FWD compared to 22 MPG AWD, over a tank, each way, in the summer. In the interest of full disclosure the AWD was used in one direction of our trip because it was raining hard (some would argue an effect). Then again while in FWD it was warm and we had the AC on, and so on.

 

 

 

When finally having my torque bind issue addressed by a Subbie experienced mechanic he was not concerned about the extra wear on duty solenoid C. By keeping it in FWD, to avoid torque bind, I saved my clutch packs.

 

 

 

DooMeSuuby might be suffering from what my 95 Legacy LS had. Alias20035 knows quite a bit on the subject of mid 90’s torque bind and directs everybody to:

 

 

 

http://www.legacycentral.org/library/torquebind.htm

 

 

 

Hope this helps add some light,

 

Rude