Today was the first time I had the disco in snow and to say it was a bit disconcerting to realize I had no idea how to correct a slide in 4wd vehicle as big and heavy as it, would be an understatement.
So how does one correct/stop a slide in a vehicle with permanent 4x4 status? My disco has Traction Control and ABS, but nothing like stability control, so how do I regain control? Do I drive out of it like I would in a fwd car, or do I slowly let off like in a RWD?
Go play in a parking lot for a while. All my limited experience was in a V6(read: underpowered) half ton chevy 4x4, usually a bit of power would correct under steer, It handled oversteer like a RWD, let off a bit and oppo. Though if you were reasonable with it it was generally just point and shoot. This was proper 4 wheel drive with no center diff though. A full time AWD will probably behave differently.
Some people here probably have more experience with 4WD than I do, but I've owned two part time 4WD SUVs for the last 7 or so years.
My experience is that in a slide situation (where the rear end kicks out), I have had more luck just letting off the gas and letting it correct itself.
However I have been in situations where its all open roads and I have steer into it, gotten on the throttle, and let the front wheels pull me straight again.
I second going into a snowy parking lot and testing out the different ways your Disco would handle in slippery situations.
For the most part, let off the gas, and all other inputs are gradual. Like Kenny said, go play in a parking lot. After a while you'll learn when to goose it, when to brake, counter-steer, etc. For the most part though, in a large AWD vehicle you're a passenger without a lot of influence once the slide starts to happen.
The trickiest part is when you manage to get into a nice 4 wheel drift. The steering (in a 4WD truck) goes numb, no clue where center is, so much inertia in the wheels that they will go from spinning to sliding without really stopping near the correct speed. You just have to kinda let it decide its time to collect the road again...and sometimes you may realize you are a turn out on the steering wheel.
In reply to Streetwiseguy:
A good butt dyno is invaluable here, just go full lock till you feel it start going were you want, then back off. This is, again, best learned in a parking lot.
You have to go and try it out in a parking lot because different 4wd/awd systems behave differently. I've driven pretty much every type of 4WD/AWD in snow, and they are all a bit different.
If I'm not mistaken, your Disco has a full time AWD. If this is the case, and the system isn't too slow to react, I would usually just keep the throttle steady, let the center differential send the power to the front wheels and counter-steer. This is the technique that I would use in my Subies and my Audi. It's fun and fast.
For a large vehicle like your Disco, I'm guessing that the extra mass and light rear will force you to slightly lift to stop the rear wheels from spinning and then go back gently on the gas to pull yourself out of the slide. But if the center diff is fast acting, you should be able to use the same technique as the Subies/Audi.
If it's a classic off-roading truck locking center diff, just leave it out of 4WD. While those systems are great to pull yourself out of a snow bank, they make for a very difficult vehicle to control when you drive fast.
The worst part is that they don't like to turn. Gradual use of the throttle is usually the best. Just remember, all wheels are driving so they want to do odd things. Slow is the best way.
What all these guys say is true but the biggest advice is to remember, 4 wheel drive is for go, stopping is the same for everyone. That thing will slide the same as a two wheel drive under braking.
I have lots of Disco specific snow experience.
They don't turn. At all. Start to turn, and it understeers. Give more gas, understeer. Give LOTS more gas, you get LOTS more understeer. I NEVER got my Disco into a drift, ever, despite trying. It will never ever ever get stuck, but that's when it is going straight. Just know that the front wheels are going to lose traction first, and you can hit the brakes to do some weight transfer to try to get more weight up there to get more front traction, but it doesn't work all that well anyway.
If you're interested, I have a set of 18" Range Rover Hurricanes with Pirelli snow tires on them still, and I'm local. Only $200, as I want them out of my shed.
Your answer is just leave it in rwd unless you actually need it to get through something.
it's permanent 4WD. I wish it had a 2wd mode.. but all 4 wheels are always driven
Does the center diff lock?
no... Land Rover decided that American's were too stupid not to drive long distances with the diff locked, so they removed the mechanism. It is on my list of things to retrofit
If it's got an open differential instead of a transfer case, it's not permanent 4wd, in fact it's not 4wd at all. It's some variant of AWD, which is distinctly different than 4wd.
It hasnt really snowed where i live since 1984, but just looking at the physics of it, my educated guess on how 4wds should be driven differently in snow.. is that they shouldnt be. Seems like the only real advantage would be making acceleration easier. Which, part of the time, manifests as making it easier to get into a slide you don't know how to fix. 
There's another thread on here right now about how some people feel electronic driving aids are making people lax and stupid and getting in over their heads. I cant help but think that a 4wd system does that for snow driving, because it doesnt help you prevent accidents nearly as much as it helps you carry more speed into them.
In reply to Vigo:
Let me paint you a picture, pickup on decent ATs, maybe even RMA snow certified, 2" of snow on road, at a stop sign, slightly uphill.
2wd:Good berking luck getting moving in any sort of dignified manner. Especially if you actually use the truck and can't have sandbags or whatever taking up space.
4wd:Pull away normally.
Now AWD cars, those are just an excuse to drive faster in nasty weather, as you said. Only time I've got a FWD stuck was high centering it, at which point you need a truck anyways.
guess it depends on the terrain where you live … I got along fairly well with snow tires on my old Civics … but occasionally we've had snows that would stop the Civics … 10"+ and they didn't do so well … even lesser amounts, with the hills (even mountains) around here, I could get into situations where I needed all 4 wheels digging …
it was a revelation when I bought my first beater Suby … snow tires on them … and even 18" of snow wouldn't stop me …
we don't have much snow now (global warming ???) but my driveway is still as steep as it always has been
and to pull the "racecar" up my driveway … a 2wd isn't going to get the job done (I've seen 2wd PU's get stuck in the summer time, when the surface gets all loosy-goosy … so snow tires and AWD (by choice) or 4wd since I couldn't afford a Ridgeline LOL
foxtrapper wrote: If it's got an open differential instead of a transfer case, it's not permanent 4wd, in fact it's not 4wd at all. It's some variant of AWD, which is distinctly different than 4wd.
it has a 4high and a 4 low transfer case.. but the mechanism to actually lock it has been removed from the factory. The gearing is still in the case, just impossible to activate without crawling under the Disco.
It's really too difficult for anyone but you to answer. Even if another LRD driver with tons of experience tried to guess, he'd be shooting in the dark due to the fact that he may have been driving on snowy ice or icy snow or powder or heavy, wet snow... Or been driving with bad tires, new tires, snow tires, wide tires, narrow tires.
Take the advice of those that said find an empty parking lot and figure out how your Discovery drives in the snow in your area.
I do agree with the general "it'll understeer like a mutha" sentiment however!
Iusedtobefast wrote: What all these guys say is true but the biggest advice is to remember, 4 wheel drive is for go, stopping is the same for everyone. That thing will slide the same as a two wheel drive under braking.
I understand your point, but respectfully disagree. Especially when driving a vehicle that has front disc, rear drum brakes. you will indeed stop better when you are in 4wd.
gofastbobby wrote:Iusedtobefast wrote: What all these guys say is true but the biggest advice is to remember, 4 wheel drive is for go, stopping is the same for everyone. That thing will slide the same as a two wheel drive under braking.I understand your point, but respectfully disagree. Especially when driving a vehicle that has front disc, rear drum brakes. you will indeed stop better when you are in 4wd.
Uh... Huh? No. You might have an argument with a manual transmission, as there is "more" engine breaking going on, but 4WD does not help with stopping at all.
mtn wrote:gofastbobby wrote:Uh... Huh? No. You might have an argument with a manual transmission, as there is "more" engine breaking going on, but 4WD does not help with stopping at all.Iusedtobefast wrote: What all these guys say is true but the biggest advice is to remember, 4 wheel drive is for go, stopping is the same for everyone. That thing will slide the same as a two wheel drive under braking.I understand your point, but respectfully disagree. Especially when driving a vehicle that has front disc, rear drum brakes. you will indeed stop better when you are in 4wd.
Yep, 4 tires, equals 4 braking points of contact, not able to change the fact that 4 braking points do all the speed reduction every time.
Not sure what the front disc/rear drum brake part means because 2 or 4WD, they still do the same amount of work whether they are 4 discs, 4 drum or a mix.
In reply to mtn:
No, he has a somewhat valid point, if you have a locked/nonexistent center diff, your brake distribution is now forced to be 50/50. This may make some trucks stop better, having very little rear brake bias to ensure they don't lock the rears unloaded.
In reply to mtn:
The heavy front brake bias, setup for normal driving, is a terrible problem for 2wd trucks in the snow. in 4wd the tires are all connected, you lock up the front, same thing happens to the rear.
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