Awd Vs. 4wd

[04hd]

Does anyone know why when you are in a 4wd truck you click on your 4wd on dry pavement and it kinda hops when turning. But on a Awd truck this does not happen. what is the reasoning for this.

[hockeypro1411]

4wd locks all four wheels together. When you turn, the outside wheels need to spin faster than the inside wheels. AWD uses a system of clutches (I think) and lets the wheels act as one unit, but spin at different speeds.

[Matt_]

AWD has a different type of T-case... its basically another differential in the center of the vehicle.

 

4WD transfer cases using a more positive locking mechanism between the front and rear axles to give better performance in off-road situations like deep mud and off-camber terrain (like rocks).

 

AWD is meant for on-road performance, better all-around traction for how most of our vehicles are driven 99% of the time... on wet pavement. But it wouldn't do very well in a mud bog or rock crawling thats for sure

 

I personally love my AWD truck now... i was always nervous when my wife took my 2005 out when it was raining since its very easy to kick out the rear end of a pickup truck. With the AWD in the Denali, i have over 100 more HP and haven't even broke the tires loose pulling into traffic in the rain, its like driving on a dry road

[VMax2007]

4wd locks all four wheels together. When you turn, the outside wheels need to spin faster than the inside wheels. AWD uses a system of clutches (I think) and lets the wheels act as one unit, but spin at different speeds.

 

Close, but not quite.

 

4WD locks the front and rear driveshafts and when you turn, your front wheels travel further than your rear wheels, thus creating the "hop". The front diff is an open diff, so the hop is not created from one front wheel to the other.

 

AWD systems do not lock the front and rear driveshafts mechanically.

[Gryphon]

I'm surprised no one's said this yet.

 

NEVER DRIVE IN 4WD ON DRY PAVEMENT!!! That hopping puts a LOT of strain on the transfer case eventually leading to expensive damage. Leave it in 2WD on dry pavement.

[svensk]

I'm surprised no one's said this yet.

 

NEVER DRIVE IN 4WD ON DRY PAVEMENT!!! That hopping puts a LOT of strain on the transfer case eventually leading to expensive damage. Leave it in 2WD on dry pavement.

At least make sure it's wet enough so the front wheels slip on turn in.

[DBVille]

I'm surprised no one's said this yet.

 

NEVER DRIVE IN 4WD ON DRY PAVEMENT!!! That hopping puts a LOT of strain on the transfer case eventually leading to expensive damage. Leave it in 2WD on dry pavement.

At least make sure it's wet enough so the front wheels slip on turn in.

 

The slipping that occurs in 4WD means one end of the vehicle is spinning its tires. On wet pavement, turning suddenly can result in the front (or rear) wheels losing traction. Bad things can result. Because the other end may have traction, the slipping end may be very slow to regain traction - either pushing you off the road, or spinning you off. Odds of this happening? Not very high, but why push your luck? Running in 4WD on pavement does put more stress on the T-case, u-joints and axles. However the most likely damage is wearing out the tires, which are forced to slip.

 

Unless you really know what you are doing, use 2WD or AWD on any paved surfaces, and leave the 4WD to dirt, deep snow, etc.

[MikeInCtown]

Just FWIW, AWD is ONLY AWD when the computer notices slipping occuring at the rear wheels. The vast majority of the time, and especially on dry pavement, the truck is in a 2wd mode. (Speaking of Bravada) This saves on fuel and drivetrain wear.

[Matt_]

Not quite:

 

AWD is AWD all the time; on GMT900 t-cases its 60% rear 40 % front all of the time.

 

Auto-4x4 is 2wd until the rear slips and then it kicks into 4wd, but from a stop it provides 20% torque to the front axle to help prevent slip, and kicks in full 50/50 if the rears do slip.

 

Put your 4x4 truck in auto mode and turn on dry pavement, it binds almost as bad as 4x4 mode since the clutch packs in the tcase are partially engaged

 

 

Two different t-cases, two different beasts

[Matt_]

I'm not sure which tcase is in the bravada though...

[VMax2007]

Put your 4x4 truck in auto mode and turn on dry pavement, it binds almost as bad as 4x4 mode since the clutch packs in the tcase are partially engaged

 

Um, no...mine doesn't, nor did my 2000.

[Matt_]

Each truck feels different. You could feel it on my 2005 and I've had customers complain about a choppy feeling in parking lots and they didn't realize they were in auto mode.

 

Ill have to see if I can find the tech article that explains the auto mode operation, I know I have the one for awd tcases saved.

[PhilB]

Just FWIW, AWD is ONLY AWD when the computer notices slipping occuring at the rear wheels. The vast majority of the time, and especially on dry pavement, the truck is in a 2wd mode. (Speaking of Bravada) This saves on fuel and drivetrain wear.

 

This sounds like the description for AutoTrac mode, not AWD.

[Nick The Great]

Each truck feels different. You could feel it on my 2005 and I've had customers complain about a choppy feeling in parking lots and they didn't realize they were in auto mode.

 

Ill have to see if I can find the tech article that explains the auto mode operation, I know I have the one for awd tcases saved.

 

I can feel a little hop when in Auto, if I turn really sharp. Not as bad as 4HI, but more so than 2HI. I don't know if there actually is a little wheel slip when turning sharp and the Auto 'kicks in' or what. I'm only in Auto in less than desirable weather, FWIW.

 

[Matt_]

Yea exactly. It shouldn't be anywhere near as choppy as being in 4x4, but its often noticeable as compared to 2wd mode

 

I guess I was a little off with my wording in my first post.... Maybe its not "almost" as bad as being in 4wd, just worse than being in 2wd lol