We all know how much fun our Subies are in the snow. I had ours on some fun snow-covered dirt tracks up in the North Cascades last month and enjoyed getting a little sideways. My tool of choice was the accelerator going up, and, even more effective, the handbrake going down.

 

It was not until I got back to town and was for some reason thinking about the Subaru AWD system that it hit me that locking the rear wheels with the handbrake while the fronts were still turning might have been very, very bad for the drivetrain. I have the 5-speed version, which means a viscous coupling. How much damage, if any, might I have done to the coupling by putting so much frictional stress on it in this way? What will happen if it goes out? Will I just have front-drive?

 

I'm worried! Thanks in advance for any replies.

I'm not exactly sure what happens when the center diff gets thrashed, but I know you won't be driving in FWD.

 

If the fluid fails (or loses it's ability to gel), you'll be driving with an open center differential. So it will drive with the 50/50 torque split, but if the front or back wheels slip the diff will transfer the power to them.

 

If the fluid seizes the diff, you'd be driving like with real 4WD. Power would be split 50/50 and the diff wouldn't be able to make any compensation. You'd get lots of binding driving around corners on pavement.

I beg to differ. If the oil in the coupling has been overheated and the molecules sheared to pieces, your Sube will be FWD.

 

Easy to check for on snowy or wet roads.

I'm not exactly sure what happens when the center diff gets thrashed, but I know you won't be driving in FWD.

 

If the fluid fails (or loses it's ability to gel), you'll be driving with an open center differential. So it will drive with the 50/50 torque split, but if the front or back wheels slip the diff will transfer the power to them.

 

If the fluid seizes the diff, you'd be driving like with real 4WD. Power would be split 50/50 and the diff wouldn't be able to make any compensation. You'd get lots of binding driving around corners on pavement.

An open diff doesn't transfer power, in fact it usually takes the power away from the place it needs it most. This is way they created LSD and VLSD diffs. Like Setright stated, the viscous fluid breaks down under abuse rendering it useless. I wonder about the tranny going to FWD if the center diff fails, since this is an AWD tranny, I have this feeling that if the center diff goes, the tranny will be useless. Now it is different with an AWD auto because they have a different system for AWD and there is a fuse that can make the tranny FWD.

you probably didn't do any damage unless you were covering a significant number of miles like this. i know two people that had their manual XT6's towed on two wheels and never had any problems. if you want to pull this move consistently you could remove the rear drive shaft. assuming it's all snow and frozen ground you shouldn't get stuck if you're accustomed to driving in snow/offroad. keep driveshaft in car just in case!

 

changing your fluids is a nice things to do for your trans, particularly with any abnormal driving conditions such as this.

Your brakes work that good? Mine suck, the shoes are fine, and the adjustment is OK. I even exercise them now and again.Tiny

of course if done right you don't need the handbrake.maybe with auto trans it's different but with 5spd it's easy.

 

(please don't take this as bragging)

Yep, MT means you just need to press the throttle hard if you want some tail-sliding action in snow!

 

 

("All We'll Drive" still cracks me up!!)

Dr.RX, the car will become FWD. The input to the viscous coupling has a direct mechanical link to the clutch output shaft and front diff.

 

grossgary: Don't XT's have a selectable AWD drive, with NO center diff?

Yeah hitting the accelerator works when going uphill, but cruising down it really gets pretty hairy...accelerating hard down snow-covered hills with big trees nearby at about 25mph makes me uncomfortable. Much nicer and safer to take it slow and sideways. All the brake needs is a quick jerk with a steering twitch to get things sliding, then you just steer and let the brake go.

 

OK, sounds like I should be fine really. It doesn't bind up around town and my traction remains good in the snow so I'll just be sure to not do it in the future, and stop worrying about it.

 

Thanks!