AWD vs. 4WD, which is preferable?
 

I have lived in FL essentially my whole life so my snow experience is slight at best.

Which is better for driving in the snow AWD or 4WD? Is a Denali AWD better than a 4WD Yukon?

In general, AWD is 4WD lite. AWD is usually an automatically-controlled system whereas 4WD is manually controlled at your desire.

AWD is for cars, 4WD is for trucks.

I don't know specifically on those two trucks but they're basically the same vehicle. It would seem to me they'd have the same driveline. Is one AWD and the other 4WD?

The awd system that I believe in that truck stays on all the time, giving traction on all slippery surfaces. It does what it's purpose is intended for, but is no 4wd, or has low gears for pulling, which might not be necessary for your application. I personally like the awd trucks.

Engine Options for all Yukon Denali Models Trim Level Horsepower Torque
(lb-ft.)
Yukon
Denali Yukon XL
Denali
Vortec 6.2L Variable Valve Timing V8 SFI 380 417

Mechanical Yukon
Denali Yukon XL
Denali
Alternator, 160 amps
Cooling, external transmission oil cooler, auxiliary, heavy duty air-to-oil
Differential, heavy duty locking rear
Engine block heater
Exhaust, aluminized stainless-steel muffler and tailpipe
StabiliTrak, stability control system with Traction Control
Transfer case, AWD, electronic automatic system
Transmission, 6-speed automatic, heavy duty, electronically controlled with overdrive, tow/haul mode, and tap up/tap down shifting

TransmissionFeatures Yukon
Denali Yukon XL
Denali
Rear axle, 3.42 ratio
Transfer case, AWD, electronic automatic system
Transmission, 6-speed automatic, heavy duty, electronically controlled with overdrive, tow/haul mode, and tap up/tap down shifting

SteeringTurning Diameter Yukon
Denali Yukon XL
Denali
Turning diameter, curb-to-curb, ft 39 43
Features Yukon
Denali Yukon XL
Denali
StabiliTrak, stability control system with Traction Control
Steering, power
Suspension, front, coil-over shock with stabilizer bar
Suspension, rear multilink with coil springs
Suspension package, Autoride, bi-state variable shock dampening and rear air-assisted load-leveling, includes automatic air level control
Transfer Case, AWD, electronic Autotrac system

It appears that the Yukon is manually activated whereas the Denail is automatic.... probably using wheel speed sensors to detect slip. They probably both have the same driveline. So if you're capable of just pressing a button when you need it, the Yukon is fine. But if you (or your wife) would rather have the computer decide when you need the transfer case engage, then the Denali is what you want.

This is from the GMC website:
Yukon- Transfer case, active, 2-speed with push-button controls (4WD models only)
Denali- Transfer case, AWD, electronic automatic system

I think the 4wd is better for the snow, although the awd may be better for ice. Its my understanding that awd does not turn all four tires. The awd is an automated system that will detect slippage in one tire and transfer the power to a front tire and/or opposite rear tire. Wheras in 4wd you can spin all 4 tires in the worst conditions.

I have both a 4WD Jeep Wrangler and an AWD Jeep Grand Cherokee. When going offroad, the Wrangler with true 4WD and low range is the only way to go. However, when it snows, the Wrangler stays in the garage and the AWD Grand Cherokee gets us around with no problems. We are on our 3rd AWD Grand and love them. Plus, with the wife driving I don't have to worry about her "forgetting" to put it in 4WD and going in a ditch or getting stuck.

The only downside is they can me more to maintain, since the front end is always pulling some you can wear out bearings and CV joints faster than a 4WD system. We seem to get about 60K miles out of the Grand before the front end needs some work but it is a small price to pay.

I agree on the AWD having higher maintenance costs and lower MPG. I just swapped the 249 (AWD) transfer case in my Grand for a 241HD (4wd). Almost direct swap. The AWD transfer case is much weaker than the 241 along with all the differences mentioned above. Drives much better all around - 2wd does "push" and 4wd seems to connect me to the road better. Wive's car? Then go AWD for sure! :D

My wife has had several Denali's and now has a suburban and I can tell no difference. The late model 4WD also has an auto option so you don't have to worry about it. We have also never had any problems with the AWD model as far as maintaince. And her new 5.3 suburban get worse mileage that the 6.o Denali, but only slightly. I would get which ever truck you like best and not worry, they are both great trucks.

All things being equal, I'd want the manual control and the low range for launch ramps.

The new GMs (GMC and Chevy) have 4WD full transfer case systems, with 2W-HI, 4W-HI and 4W-LO; as well as an AUTO-4 setting. As soon as slippage is detected, the front end starts to grab. The delay is noticeable, but minimal. This setup works well. The Escalades and Denalis are AWD all the time systems.

Ideally, you would use the setup:
Normal conditions: 2W-HI
Heavy rain and/or onset of winter conditions: Auto-4
Driving in snow: 4W-HI
Pulling someone out of a ditch: 4W-LOW
Driving on ice: STAY HOME All the tire turning capability in the world won't help you STOP. ABS is a great technology. It allows you to somewhat convince the vehicle to slide out of control into a different direction. That's about it.

The difference in the GM systems, AWD vs 4WD is mostly in the front axle. The AWD systems don't lock the front axle and power is distributed to the front by a viscous coupling. 4WD systems (manual and electric) provide an electric full locking front axle and power is transferred using a chain system in the transfer case. The 4WD systems with the "Auto" button have electronic transfer cases so that when "Auto" is selected, the front axle is locked and when F vs R slippage is detected the t-case splits power to the front axle.

The biggest drawback to the AWD systems is lack of locking front diff. The situation was worsened early on because vehicles were available without a rear locking diff. So if somebody cheaped out on the option list, they could be in a situation where wheels on opposite corners were spinning free.

For the family grocery getter driven in mild to medium conditions, the AWD will be the better platform for the control it provides and ease of use. I personally like the increased flexibility of the electronic 4WD offered in the "standard" class of SUVs like Tahoe, Yukon and Suburban.

2WD with shift on the fly 4WD is the best. There is hardly a need for AWD unless you own an Audi or comparable car that is built around it. 4WD on trucks means the t-case is locked and will send 50-50 front and rear no matter what. There are no full time locked axles on any truck(except the jeep rubicon and dodge powerwagon front and rear, some toyotas-4 runner etc ONLY REAR, and those are all selectable). All are glorified limited slips...some are better than others. No manf puts limited slips in the front axle either(harder to turn.) The auto 4wd system(AWD), as found in GM trucks, tries to decide when it needs to engage and you can feel it surge fwd when the back spins out. Just put it in 4wd hi and forget about the jerky computer controlled crap. Put it back into 2wd when you dont need it.

Denalis etc have only AWD...different t-case, and do work in a more seamless manner than the awd found in dual use 4hi-lo-awd-2wd as found in other trucks. But you dont have 4lo, and the t-case cannot lock 50-50 front rear. GM calls there limited slip the G90 locking axle, but it is not locking. Like i said above....no manf puts real lockers in their trucks except the rubicon, power wagon, and some japanese trucks...4 runner etc. Only the rubicon and p-wagon have the locker in the front, and ALL are selectable on/off.

In order to make a locker or a limited slip in the front axle easy to drive you need to have auto or manual disengage hubs, or a fully selectable unit like an ARB, or detroit e-z.

It totally depends on the truck.

In some cases you can get both. my navigator has awd, 4wd hi, and 4wd lo. No 2wd. In normal driving, only the rear wheels get power (and there's a limited slip back there). When the rear wheels spin, the computer detects it and locks up a clutch in the transfer case to send power forward. If the clutch is active for too long, it automatically engages 4x4... which is a dog ring in the transfer case tying the front and rear together just like a typical 4x4 transfer case. If I want low range, I put it in neutral, hold the brake, and engage 4 lo.

In my dad's envoy, he has all the same options plus 2wd. In 2wd, it just shuts off the clutch feature and leaves it in 2wd all the time.

In a lot of vehicles, all you get is AWD. This is not as desirable as an option with AWD, 4x4 and 4 Low.

I would personally rather have all the options, like my dad's envoy. AWD is nice for the snow, because you don't have to worry about turning it off if there's an area of dry pavement. 4x4 is nice for off road, low range is nice for the launch ramp, and 2wd is nice when you want to do a big smoky burnout.

Oh... and almost no production vehicles (save for those mentioned above with lockers) have any type of locking or limited slip front differential. Very few front wheel drive cars are available with a quaife limited slip / locking diff (not sure on the exact functionality of that unit) but almost no 4x4 or AWD vehicles have anything but an open front diff. If a manufacturer claims to have a feature of this type on their front axle, it is almost always a system where the ABS detects wheelspin and applies the brakes on one wheel, thus sending power to the other (like the caliber srt4).

Rears frequently get limited slip from the factory (or GM's crappy "gov-lock" POS, if that's still around) and often get a "locker" aftermarket, either manual (cable, electric, or air actuation) or automatic (sensing wheel spin and engaging a lock not based on a clutch). True "lockers" are kind of finicky on the street and are really more for off-road use.

As quoted from my 2001 Yukon XL owner's manual:
So GM's 4WD front axle will indeed LOCK via electronic device. The rear axle is GM's excuse of a "locking" diff, but it does work at low speeds and throttle input, like a slippery ramp. A true limited slip would be great; do they make one for the 14-bolt axle?

When they refer to locking your front axle they mean it gets 50% of the torque, no more, no less. The transfer case is an electric selectable version...not lever. You do not have any type of locking mechanism in your front differential. The only front lockers available on any production vehicle are those found in the jeep rubicon and dodge powerwagon. Both are very similar to a detoit e-z locker and selectable. The GM G90 rear axle feture is their limited slip option that comes standard on z71's etc. it is a clutch type limited slip....dont know why they call it a locker. Ive installed detroit lockers on my previous full size bronco(with warn manual hubs so i can turn) and big difference...almost like welding the spider gears.

Well tell ya' what, you define "locking" for me. I'm pretty sure I understand the difference between the transfer case splitting power to the front axle and "locking" the front axle. When 4WD is activated, it's pretty obvious when you turn that the front axle is locked.

As for the rear diff, GM's unit isn't a clutch type, at least not what I think of (like an Auburn) when I think clutch type diff. It's made by Eaton, and it's totally open unless you spin a wheel below 20mph. If you spin a wheel at slow speed, it spins weights inside the diff to "lock" both wheels. The axle will stay locked until you go over 20mph. The engagement is about the worst I've felt, and in my truck it's pretty easy to spin a wheel over the "disengage" speed before it ever engages.

I have a escape with auto awd, but you can lock it into 4wd when it is messy out. works amazing, the little suv is a beast in the snow with good tires. have a suburban that has 4wd, is amazing in the snow in 4wd, but if in 2wd is pretty crappy. the auto awd system works fantastic

I had a AWD Astro service van for awhile and in heavy snow I gotta admit it was pretty phenominal.......after a couple of minutes you didnt really even know it was on .......you just drove around normally with awesome traction.......
Although even up here theres only probably 5 or 6 days a year that you REALLY need it.......and the question was snow not launch ramps......

How does GM define front axle locking....you have now locked the front diff into 4WD. Feel free to look it up yourself....there is nothing in the factory front diff of your truck. Its an open 8.25" aluminum case POS. I have the same thing. Would break if a locker was in there. What you feel when you put it in 4wd is the weight of your truck and input torque from the motor. Both tires will spin/pull with equal resistance on them....its the way an open diff works. You can turn b/c its open, otherwise your tires would chirp, and the axles would chatter about and you would kinda plow forward. The rear G80, govlock, or whatever, is called a locker and it does sometimes lock under 20 mph. But it takes one wheel spinning, the other not, and nothing over 20mph to do it. Overall its a very week unit. A real auto locker like a detroit, that has weights too, should always engage when power is applied, and free wheel when not, so you can turn easier. Badabing

What they mean by locking front axle is how the axles are locked to the diff.

Chevy's do not have locking hubs, the axles are directly attached to the break rotors/wheels. The disconnecting of the axles from the diff is done at the differential by an electric sleeve. Auto locking means you don't have to get out and manually lock the hubs (axles to the diff). There is still just an open differential.

Ford uses auto/manual hubs on its trucks, a much better design IMO.

I prefer 4x4, not all wheel. AWD takes a lot more power to turn, uses more fuel and compromises on 4wd function. Plus, if I want to light up the rear tires and put the truck sideways, it just isn't happening on AWD. Thats why I hate the trailblazer SS.. could have been such a cool truck, but they put AWD in it.

Joe

Ahhhh...you can get the TBSS in both AWD and RWD. I test drove on 08 RWD the other day (very bad azz.) Im getting an AWD for my wife.

sorta been covered already, but in this case there is one of two things going on. Either the front hubs are locking, or the front differential is engaging to the axle shafts.

My suburban had auto locking front hubs. When you put it in 4x4 and hit the the gas, the front hubs would lock. This would likely be referred to in the manual as the axle locking up, becuase the manual is usually pretty well dumbed down.

In my S10, there was a vacuum switch on the transfer case that actuated a function similar to a locking hub, except it was at the front differential. The axles always spun with the wheels (IFS, so halfshafts actually) but the front driveshaft would not turn with the front halfshafts unless this little vacuum switch told it to. I'm not sure if this locked the halfshafts to the diff, or the axle to the diff, but one way or the other it "locked up" the front axle. And it was most certainly an open differential, whether it was "locked" or not.

Lots of confusing use of the term "locked" floats around. It takes some experience with different vehicles to really understand what's going on.

The front is by no means locked in your truck. Open front differential means that it will only spin the tire with the least amount of traction, or both if the traction is equal.

The GM rear is a complicated locker that sometimes works and sometimes doesen't. It is much less noticable on the street than a detroit, lockright, etc. and that is the purpose. There are plenty of Limited slips available for the 14 bolt but they are no better than what you have and will not completely lock. YOu can get lockers that actually work for the 14 bolt, but you probably won't like them on the street.

There are way too many different AWD systems out there to lump into one category. The quadradrive in Grand Cherokee's works very well on the street and off road and will actually lock the differentials, even the front. The denalli is setup for slick roads and works great for that, but offroad you will be disappointed. I drive a navigator and it has AWD 4 high and 4 low, and I very seldom touch the switch. I get a little better mileage than my dads f150 without AWD too.

If any of you guys want a demonstration of locked and unlocked let me know.

This is locked at both ends ;)
http://i36.photobucket.com/albums/e7...d9a41aaff3.jpg