AWD/Full-Time/Centre-Diff vs Part-Time 4WD in greasy snow?

[p nut]

I've always left the 4WD engaged on freeways. Never had binding issues on patchy roads. Just remember to take it out of 4WD when you get into town. Found out the hard way and fortunately only blew the seal on the xfer case.

And the max speed comment, yes, that is for engaging only. Thanks for clearing that up.

 

[Mrknowitall]

If everything is properly maintained, there's no reason highway speeds in 4wd with a part time vehicle would do anything bad. Other thoughts on what I've read here, and what I've learned...
*Old Stuff-When I lived in the UP, we would lock the front hubs in October and un-lock em in April or May. no wear problems. With a manual t-case, you can switch in and out of 4wd at ANY speed- all the parts are already moving.
*With newer stuff- Some 90's and early century vehicles had ABS that would not work in 4wd. The merits of ABS is a different discussion, but its worth mentioning.
*On the highway, going mostly straight, even with sweeping turns, 4wd will not do anything adverse vs AWD.
*Where awd is nice over part time is around town- I find myself needing 4/AWD one minute to accelerate through sloppy patches, and then pulling into a well-salted parking lot, where locked 4wd would bind. Makes for a lot of extra shifting.

I think my next tuck will get a multi-mode t-case transplanted. While multi-mode systems seem to be the norm for truck-based SUV, they're still few and far between in Pick-ups, and often option group restricted.

 

[drsmonkey]

There are a lot of interesting opinions in here.

I drive a lot of different AWD and 4wd vehicles of every flavor in winter conditions about 6 months out of the year for most of my life. This is all you need to know to make the AWD/4wd decision.

Simplified version for the OP's question ignoring other disadvantages and advantages...

AWD/4wd only helps a vehicle to accelerate in the direction of travel or hold speed against resistance, that is it. All other dynamics (braking, cornering, etc.) are dictated by other factors (vehicle weight, COG, tires, electronic nannies, etc.)

Once at highway speed it doesn't matter much if you have AWD/4wd/2wd unless you are trying to accelerate, go up a hill, or pushing snow. I almost always switch back to 2wd mode once the vehicle is moving on flat slick surfaces, and only switch it back on just prior to needing to accelerate. If you need 4wd above the speed at which it will engage/disengage you are probably going way to fast for the conditions. At Freeway speeds I would much rather be driving a smaller AWD or FWD with good snow tires than my truck in anything other than deep heavy snow because it will stop and corner much better in an emergency and is less likely to roll if things go sideways.

I see AWD as a convenience, it automatically drives the needed wheels without any driver input making it easier to go from dry to slick conditions and back. 4wd needs to be selected by the driver when needed and turned off on high friction surfaces to avoid damage. That being said not all AWD systems are created equally.

DRS

 

[DaveInDenver]

Probably important to mention also that I have a Aussie Locker in the rear and 270K difficult miles on the '91, something to consider when talking about driveline wind-up.

I'd assume selectable 4WD does impact braking and steering more than coupled 4WD because if the rear axle locks up it stops the front from spinning, too. They are locked together without exception. I generally descend in 2WD, for example, so that the front wheels keep turning if I lock the rears. ABS tends to have more control over being able to release a single wheel I think. Although couldn't say how that impacts the others yet. I'm just a month in with the Tacoma. I have the old fashioned ABS on the '91, it pulses at whatever speed I can pump the brakes...

 

[Aquafbody]

How fast can you drive in a locked in 4x4? As far as I remember, my Frontier could not go past 45-50ish without risking damage. Full-time AWD wont require that you anticipate when you need to move power around, or activate certain switches and knobs.

4 hi or 4 lo? in 4 lo not very but then again it's not meant to. My S-10 tops out at around 90 in 2wd I've never had it past about 50 or so in 4wd but I wouldn't be surprised if it could go faster. I'm in Colorado and I have lived here my whole life so snow doesn't really bother me so I'f i'm locked in 4 it's usually pretty nasty and to dangerous to go much past say 40 or so.

 

[Loubaru]

My previous "fun" car was a WRX STi which was an absolute blast to drive in the snow....and very hard not to get yourself in trouble. I have no clue how I never wrecked that car, especially considering I bought it when I was 22. Part of the reason why I was set on the 99/00 4Runner was because of the transfer case which has the push button AWD. I've only driven it a couple times in the snow which was when I was still on street/car tires but it handles surprisingly close to my STi and was a lot more stable than I thought it was going to be. For a relatively heavy/lifted vehicle it was WAY easier to throttle steer than I expected. Also, It being lifted on crappy tires it lost traction much sooner than my STi did which is slower but also more fun :smiley_drive:.

When I locked the center dif in the STi (4WD) or put the 4runner in 4hi the front wheels push really bad when doing "spirited" cornering. Long story short 4WD is fine and will get you there safely. IMO AWD is only nice for higher speed driving, probably higher speeds than you should be driving, and getting the *** end out.

 

[carbon60]

My personal experience has been that my 4runners (all part time 4wd with a standard transfercase) are more squirrely in the snow than an AWD Subaru.

FYI, many 4runner models have full-time 4x4 with a centre diff.

If you're talking about a vehicle stopping and turning safely at higher speeds, then don't get too caught up in the drivetrain. Stopping will be the same since all vehicles have brakes at all four corners, what you really need is a good set of snow tires. It's really the same deal with turning, though a lower, lighter vehicle will be easier to control. A good example being the aforementioned Subaru.

Yeah, lets ignore stopping. Interesting point about COG and weight. I do believe that a symmetrical AWD system like my Impreza does help to keep the vehicle under control when turning at speed on a surface with less traction. I was under the impression that a full-time 4x4 would actually hinder that type of driving.

Thanks for the comments!

 

[carbon60]

When I locked the center dif in the STi (4WD) or put the 4runner in 4hi the front wheels push really bad when doing "spirited" cornering. Long story short 4WD is fine and will get you there safely. IMO AWD is only nice for higher speed driving, probably higher speeds than you should be driving, and getting the *** end out.

I've had some excitement in the Impreza, for sure. And it was only 175 HP.

I actually found, assuming I had enough clearance to get through the snow, that the Impreza was much easier to control than pretty much anything else I've driven (at speed). The low COG probably was probably responsible for 50% of that. I find the 80 handles in a similar, but much heavier fashion, when cornering. The major difference being that, when the 80 starts to get away from you, you just hang on for the ride; whereas the Impreza was actually very predictable and often easy to regain control of.

A.

 

[Martinjmpr]

FYI, many 4runner models have full-time 4x4 with a centre diff.

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The only ones with full time 4wd are the 4th gen V8 models (2003-2009) and the 5th gen (2010-present) limited models.
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99-2000 Limited 4x4 and all 01-02 (3rd gen) 4wd models have multi-mode 4wd with a lockable center differential. The way they activate is a little bit different between them but they generally work the same way.
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4th gen (2003-2009) V6 4x4 models also have multi-mode 4wd with a lockable center diff.
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All other 4x4 4runners including all 1st gen, all 2nd gen, 3rd gen models through 1998, 3rd gen SR5 models through 2000, and all 5th gen non-limited models have conventional 4wd with no center differential.
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Interestingly, multi-mode 4wd has always been available on the Sequoia and still is.
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NOTE: By "multi-mode" what I mean is that you can either run the vehicle in 2wd, 4wd with the center differential open (essentially acting like a full time 4wd vehicle) or 4wd with the center differential locked (like a conventional 4wd vehicle.)

 

[nater]

I too have found that AWD is a bit better than 4WD in the snow... This experience comes from driving my 3rd gen 4runner with the multimode case and my 6 speed FJ cruiser which is AWD all the time with a locking center diff for 4wd

 

[carbon60]

The only ones with full time 4wd are the 4th gen V8 models(&#8230

I guess by full-time, I mean anything that has a centre diff. Lockable or not, selectable or not. By that measure, most MY of the 4Runner with all the engine options, count.

On the other hand, the really-not-my-choice automatic 2012 Mazda 3 that I usually drive to work, with its factory winter tires, seems to have zero-wheel-drive. I almost have to drive in my socks to be able to get it to move from a stop in the snow. I feel like I'm in a rally at 120 kph when I'm doing 30 in 2" of snow, fighting to keep it going where I intend.

 

[AxleIke]

I don't know how many models these days have the center diffs.

When I posted, I was referring to the 4runners I had personally owned and driven in the snow. I was speaking to my experiences which were never with full time 4wd in a 4runner. I didn't mean to imply that all 4runners were the same.

 

[libarata]

When it comes to snow, I prefer my Forester over what my Frontier was capable of. The frontier went, but it was not as stable.

 

[Desert Dan]

With the center diff locked binding can occur when turning. When binding occurs it may cause wheels to slip/skid on snow/ice. At higher speeds with good traction on flowed roads I'd run in 4Hi with the center diff un-locked. At lower speeds I'd lock center diff.

 

[Arktikos]

AWD/4wd only helps a vehicle to accelerate in the direction of travel or hold speed against resistance, that is it. All other dynamics (braking, cornering, etc.) are dictated by other factors (vehicle weight, COG, tires, electronic nannies, etc.)

Once at highway speed it doesn't matter much if you have AWD/4wd/2wd unless you are trying to accelerate, go up a hill, or pushing snow...

Hard to disagree with this. My preference is a relatively heavy AWD subaru with ABS brakes on snow and ice. Jacked up 4x4's with wide tires are, in most cases, more dangerous in slippery conditions than FWD cars, in my experience.