AWD versus 4WD

Long story, but I ended up with a nice 2007 GMC half ton pickup, and it has All Wheel Drive. It's never been off the pavement, but I will be using it around the farm and it will get in the mud sooner or later. There is no engagement, the front wheels are engaged all the time. There is no hi range / low range. In fact, there is nothing that would even indicate that you have AWD unless you look underneath and see the transfer case, etc.
So how well does AWD work versus 4WD in mud or snow? I grew up in snow country, have had a lot of experience with 4WD, what should I expect out of this?

I didn't know there was such a critter.

We recently got our first AWD. It has a switch which supposedly turns it into a 4 WD. You have no such thing? Seems like in the serious going, that could be trouble.

AWD is suppose to use abs and other sensors to maintain traction but fwd normally has slightly different gear ratios to make the front pull s faster than the rear.

I am fairly sure it is like a Olds Bravada we had, where the transfer case is like a open differential, and can transfer power to either front OR rear driveshafts, but not lock front to rear. Years ago I had a full time 4x4 pickup, but the transfer case had a lock so in tough going it would lock front and rear together. They work fairly well, but without the ability to lock the front to rear it is possible that the front or rear can lose traction, and one or the other will spin. The old full time 4x4 I had also had rear locking differential, and when the transfer was locked, that truck was nearly unstoppable. Maybe someone can confirm, but usually all wheel drive vehicles usually do not have the capability to actually lock the transfer front to rear which is desirable in tough situations.

sensors tell it where to apply the power. Daughter had that on a Mazda Tribute and it would get stuck before the computer would help-worthless in my opinion

GM had troubles with some of those of roughly that era when people used them to plow snow--the nature of snow plowing is that you ARE going to slip and spin, and the programming didn't allow it, rendering them pretty much useless as plow trucks. The folks have a 2005 3/4-ton and that's fine as a plow rig, but it also has 2H/4H/4L selection. Believe later models either added an override, a different mode, or some other fix--not sure exactly what. Worst one I ever saw was a friend who bought a brand-new Kia minivan of about that vintage. What an unutterable pile of manure THAT thing was--among many other issues, the AWD "logic" simply applied the brake to whatever wheel was slipping, as soon as it slipped. If all 4 wheels slipped, there you sat. His driveway is on a tiny, almost unnoticeable downgrade from the road (I'm talking a couple inches in 40 feet) but it was enough that if there was the slightest bit of snow, ice, or even wet grass and the wheels slipped WHATSOEVER, you went nowhere--the van simply sat there. On several occasions, we had to manually push it into the road (again, with NO help from the van--it would NOT spin a tire, and there was NO over-ride of any sort) in neutral before it would get enough traction on all 4 wheels at once to go. Even sand under the wheels wasn't enough--the tiniest slip and the wheel got braked, and as soon as all 4 slipped, it was time to start pushing. It was quite a relief when someone kindly totaled it for them, luckily without major injuries to anything but the van.

I have an '01 Dodge Dakota with AWD. It has a selector for AWD, or 4HI, or 4LO.

In all wheel drive, all the wheels will drive, but the front and rear axles are connected through a differential, meaning if one axle starts spinning, the other slows down. There is no binding on dry pavement. It handles ice and snow very well, and is a joy to drive in the winter in normal driving conditions, good skid recovery. I CAN make the rear end break loose, but I have to TRY to.

Put it in 4 HI it will lock the front and rear axles together and drive just like any other 4x4. Same with 4LO. I go there when the snow is deep, the conditions warrant it.

Since it is selectable for normal 4HI/4LO I consider it the best type of AWD system to have. It's not smart at all, no computer traction controls, I wouldn't mind if it had traction control, since it can be shifted to normal 4x4. However, I don't think anyone makes them like this anymore, which is a shame. I'd love to have another. Even better in an SUV for the wife.

Brandon

Sounds a lot like our old Jeep Cherokee. Except that someone else got the best out of that vehicle before we got it, and the transfer case didn't work quite right.

Then I got the wife a small 4x4 pickup with push button control. But she was never sure when to use 2x4 vs 4x4.

Now we've got this Jeep Patriot AWD, with a switch to engage 4WD. Time will tell!

Wife has an AWD Ford Escape. No driver controls : all computerized. Like driving on clear dry roads even if on ice or snow pack. Don't help it stop but goes great.

The newer AWD systems in chevys use a clutch pack in the transfer case to apply power to the front (or rear) axles incrementally. If the computer detects a speed difference of a certain magnitude between wheels (slippage) it will apply the clutch pack just enough to even out the flow and stop the slip. These systems are extremely sensitive to differences in tire diameter. A difference in diameter of as little as one fourth inch can fool the computer into thinking one tire is slipping, resulting in constant partial appication of the transfer case clutch pack, and premature failure of the clutch due to overheating. Tires must be replaced in pairs, and measured for size, using a stagger guage, as even 2 tires of the same make can vary a little. If you have one tire ruined for any reason, the tire store will try to sell you a pair for that reason. Better listen to them, because it's true. And that goes for front to back as well as side to side, so one ruined tire may end up costing you the price of a whole set.

We have a 08 Patriot. 4 wheel drive works flawless. Never have locked it in 4x4. They have automatic yaw control also. But now much clearance under it. Ours has a life-time warranty too. But has never covered anything that has wore out. Like ball joints. Like someone said. 4 new tires. Each time.

thanks. I never even heard of a stagger gauge. Looked it up, learn something new every day. How close to tire diameters have to avoid problems?

I believe they have to be within one fourth inch diameter of each other to be ok. Any more than that will cause problems.

JeffB has the proper answer.

LOL. Sounds like Chevy is using the same drivetrain as what the AWD Ford Aerostars used to use.

Narrow tape measure works for measuring stagger

I believe you have the GMC version of the Chevy Silverado SS. In other words, a "sport" pickup optimized for street performance rather than work. Not really what you want if you're going to be doing a lot of towing or plowing snow. The advantage of AWD for a passenger car is that it's always there when needed; the driver doesn't have to think about it. Since your pickup was intended more as a passenger car than a truck, it has AWD.

Note that with AWD, there is no way to lock the center differential as there is with a "full-time" 4WD vehicle. Most AWD vehicles rely on traction control to limit wheel spin.

Wife had an AWD V8 explorer.Normally rear wheel drive until spin/slip was detected then some torque was sent to the front wheels.When that happened it was undetectable to the driver,absolutely seamless when sending tor. to the front and releasing it when it needed to.That car did really well in snow.
She has an escape,V6 and I think it's called intelligent AWD.Front W D but has a button to push when the fronts spin sending tor. to the rear.It's good in snow too but not as good as the EX.No low range in either though.
My truck-manual front hubs and an extra lever on the floor right next to the 6 speed manual shifter.

My Ford Expedition (2000 Eddie Bauer model) has a sort of dual mode AWD/4WD. When left in auto mode the front will kick in if slippage is detected at the rear wheels. You can also select 4WD high or low. For low you do have to stop, put it in neutral then select low, then go. One neat feature of 4WD low... the air suspension will jack up the body another inch. Works very well, even on an old vehicle like this.

I call AWD idiot proof driving. Prefect for someone like my wife who wouldn't put her vehicle into 4WD until after she slid off the road into the corn field. She still argues with me about this. That is why I chose a Chevy SUV with AWD for her when we bought a new vehicle for her.