Engage FWD Required with Chains?

[Quest]

A good question I saw raised and also have....

 

I have a 1997 Subaru Outback. I recently was off road in the mountains and woke up to 14 inches of snow. For the first time I chained up my fronts and worked my way back to logging roads and then down the mountain. When I

was telling a friend about it the next day, he asked if I put the FWD fuse in. I checked the owner manual and it did not mention changing to FWD. It indicated the following:

 

Driving on snowy grades or icy roads may require the use of tire chains, to which case put the chains on the font wheels only. Use only SAE class S type chains that are of the correct size for your tires so as not to damage the vehicle body or suspension. When driving with tire chains, drive at speeds below 19 MPH.

 

Is it required or is the any reason one should change FWD? At these speeds and conditions, it seems like the last thing you would want to do.

[zyewdall]

Huh? Sounds confusing to me? I can see that putting chains on increases the effective diameter of the front tires, but if you need chains, you probably have plenty of slip available to avoid torquing the driveline. But if this is a problem why not put chains on the back too to prevent this? The recommendation to not put them on the back wheels is really what confuses me.

 

Zeke

[Legacy777]

you don't need to disable the AWD, that's counter productive for putting chains on....

[tunered]

Huh? Sounds confusing to me? I can see that putting chains on increases the effective diameter of the front tires, but if you need chains, you probably have plenty of slip available to avoid torquing the driveline. But if this is a problem why not put chains on the back too to prevent this? The recommendation to not put them on the back wheels is really what confuses me.

 

Zeke

the reason not to put them on the rear is that the front is 90-95 percent of your drive,if you put them on the rear you would have to spin the front tires to get the rear to drive.

[zyewdall]

the reason not to put them on the rear is that the front is 90-95 percent of your drive,if you put them on the rear you would have to spin the front tires to get the rear to drive.

 

I thought the manual transmissions were 50/50 front and rear? Or is that only after it senses front slip? The whole AWD systems confuse me. I like my 4wd better (or at least I understand it better )

[tunered]

I thought the manual transmissions were 50/50 front and rear? Or is that only after it senses front slip? The whole AWD systems confuse me. I like my 4wd better (or at least I understand it better )

i dont think manuals have a fuse,never had one so dont know?

[dpoppeli]

Original poster said he had a '97... assuming automatic. I believe torque split was biased way more toward front then current models (auto only).

 

 

I thought the manual transmissions were 50/50 front and rear? Or is that only after it senses front slip? The whole AWD systems confuse me. I like my 4wd better (or at least I understand it better )

[rweddy]

I thought the manual transmissions were 50/50 front and rear? Or is that only after it senses front slip? The whole AWD systems confuse me. I like my 4wd better (or at least I understand it better )

Yes Manuals are 50/50, most auto's 90/10 until slip.

[Sweet82]

I thought the idea of chains up front was to dig a trench for the rest of the car?

 

With 4WD you want your traction on the wheels that steer. You can change the direction of the car better with traction up front. Traction in the rear will just push the front wheels, possibly not in the direction you wanted them to go.

[zyewdall]

I thought the idea of chains up front was to dig a trench for the rest of the car?

 

With 4WD you want your traction on the wheels that steer. You can change the direction of the car better with traction up front. Traction in the rear will just push the front wheels, possibly not in the direction you wanted them to go.

 

Didn't think of steering, but I was in a situation once where I couldn't steer in 4wd because the back wheels had enough traction to just skid the whole car in the straight line, but in front wheel drive, the front wheels could steer just enough to get out of the rut that they were in. Once back over the offending rut under the snow, I put it back in 4wd though.

 

Trenching acutally can be one use for chains, but only if you are in pretty hard or crusted snow, which is dangerous to try in subarus because you'll high center. And you have to be spinning them pretty good to trench anyway.

[knelson]

Didn't think of steering, but I was in a situation once where I couldn't steer in 4wd because the back wheels had enough traction to just skid the whole car in the straight line, but in front wheel drive, the front wheels could steer just enough to get out of the rut that they were in. Once back over the offending rut under the snow, I put it back in 4wd though.

...

 

Been there, done that - but at the time I was too frazzled to think about pulling the FWD fuse. Slid into a ditch on the side of a snow-covered logging road. (Won't go into the embarassing story of how I ended up there to start with!) Couldn't drive out of ditch - I could steer a little ways out of it, but then the back tires would staighten me out and pull me back in. Finally just shoveled out a trench and drove out. Later realized that the AWD was actually working against me in that case, and made a mental note to remember to pull the FWD fuse if ever in that situation again.

 

Just something to keep in mind if you end up in that situation.

 

On topic, I've used chains on the front end of my 94 Legacy Automatic and didn't pull the fuse. No issues, no problems.

 

-Kurt

[nickb21]

Having understeer from too much power to the rear wheels makes sense, hopefully slowing down would help get the fronts more grip though.

 

If the snow is pretty deep, i would think it would be best to manually select 1st or 2nd since it locks the power split at 50/50. At least that's what I've read, not sure if it applies to that year 4eat.