winter snow mode diff lock?

[sideways sid]

Why don't cars come with a diff lock for snow?

Seeing loads of cars struggling to move up a slight incline with one wheel spinning on ice and the other wheel stationary on cleared tarmac makes me wonder if the electronic traction control can be used to mimic the diff-lock effect in a Land Rover, keeping the driven axle(s) going until both wheels have traction.

A mechanical locking differential would add cost, but I imagine that the software and hardware already in most cars could already do this.

Obviously you couldn't use it at speed but perhaps in first/reverse only, up to 10mph or something...

[thinfourth2]

The Honda accord the wife owned did exacty this.

Also landrovers with traction control also do this

[mk1matt]

My old Audi S2 had one. Disengaged above 15mph IIRC. The main problem was that yes, it helped it get going but once both rear wheels broke traction, it was all over the place. I remember once pulling away with the lock on, giving it a bit too much throttle, and the back stepped out almost into the other lane (road camber didn't help this).

At least with one wheel spinning and one stationary, the car was stable.

For the enthusiast, yeah, it does help if you're very careful with the pedals. For the general public, ummm, no, probably not a great idea

[Alicatt1]

On the Landy RRS the eDiff is an optional extra on most models and standard on the newer supercharged versions.
But you have to drive with a very heavy right foot and have a lot of steering on to get it to lock up in snow/ice.

[thinfourth2]

mk1matt said:

My old Audi S2 had one. Disengaged above 15mph IIRC. The main problem was that yes, it helped it get going but once both rear wheels broke traction, it was all over the place. I remember once pulling away with the lock on, giving it a bit too much throttle, and the back stepped out almost into the other lane (road camber didn't help this).

At least with one wheel spinning and one stationary, the car was stable.

For the enthusiast, yeah, it does help if you're very careful with the pedals. For the general public, ummm, no, probably not a great idea

That was actually a proper mechnically locking diff

[balls-out]

you need the have proper 'power' brakes, rather than the older vacuum servo-assist. Don't know about new cars, but only premium cars used to run this sort of setup.

My old ranger rover classic had the full powered system, I was shocked that in a power brake system failure, residual braking was 2 pots (of the 4) on the front wheels and nothing at the back. Thats progress for you I guess.

[mk1matt]

thinfourth2 said:

mk1matt said:

My old Audi S2 had one. Disengaged above 15mph IIRC. The main problem was that yes, it helped it get going but once both rear wheels broke traction, it was all over the place. I remember once pulling away with the lock on, giving it a bit too much throttle, and the back stepped out almost into the other lane (road camber didn't help this).

At least with one wheel spinning and one stationary, the car was stable.

For the enthusiast, yeah, it does help if you're very careful with the pedals. For the general public, ummm, no, probably not a great idea

That was actually a proper mechnically locking diff

Yep, seriously overengineered, industrial looking thing too. Audi - where did you go wrong? Some of the S2 guys put in switches to override the speed cut-off so they were permanently locked, resulting in some fantastic sideways action.

Anway my point was - in theory the effect would be the same on a 4WD or 2WD car. My little "incident" was deliberately provoked, so I was prepared to catch it. Give something similar to the person who put snow chains on the front of that 1 series and I'd expect an accident!