2014 gmc z71 slt drive across the USA and two questions for anyone tha

[fondupot]

For those who care, I did figure out how the hill descent control works. If you push the button for it in the center console, and at the same time push the cruise control button on the steering wheel, the hill descent control will engage.

 

I thought hill decent control was for slow speeds. Not on the highway.

[fondupot]

In regards to the auto four wheel drive, I leave it on for pretty much the whole winter with no ill effects.

 

Auto 4x4 is not needed for dry pavement. This is a waste of fuel since you are running with the transfer case engaged.

 

2wheel hi - Normal, dry pavement all year round, normal road contitions.

Auto 4x4 - wet pavement due to rain or light snow.

4x4 Hi - wet pavement due to heavy snow, keep speeds below 35. And offroad.

4x4 lo - offroad, LOW speeds.

[crushNchowda]

WHat happens w/ 4x4 auto on and driving like 70 then the front wheels slip? I don't know the answer but this is why I don't F w/ it period. I'd rather just use snow tires in 2WD and only put it in 4x4 hi when I'm on back country/unpaved roads covered in snow or muck.

Auto 4x4 is not needed for dry pavement. This is a waste of fuel since you are running with the transfer case engaged.

 

2wheel hi - Normal, dry pavement all year round.

Auto 4x4 - wet pavement due to rain or light snow

4x4 Hi - wet pavement due to heavy snow, keep speeds below 35

4x4 lo - offroad, LOW speeds.

[fondupot]

WHat happens w/ 4x4 auto on and driving like 70 then the front wheels slip? I don't know the answer but this is why I don't F w/ it period. I'd rather just use snow tires in 2WD and only put it in 4x4 hi when I'm on back country/unpaved roads covered in snow or muck.

.

 

 

If you are driving 70 mph and are in a situation where you're wheels may slip, then you are doing something wrong, and are driving WAY to fast for the conditions. No amount of 4 wheel drive is going to be able to keep a 7000lb truck going 70 mph from spinning out of control if the conditions are bad. i.e. wet/slick/ice covered/snow covered.

 

90% of having a 4 wheel drive vehicle is knowing when to use it, and using it in the right conditions. If someone wants to fly down the highway in harsh weather with snow and ice with their 4x4 engaged because they think it makes them invincible, they deserve a Darwin Award.

 

 

Sent from my iPhone.

[rocnrol]

Fondupot, you are correct in that auto four wheel drive is not needed for dry pavement, but where I live in the winter, you never know what the roads will be like, black ice or whatnot. And while the main roads in town are often dry, the secondary streets are often atrocious. As for what happens at speeds, that's the beauty of driving with this system . nothing happens! In the sense that there will be cars in the ditch ever where, but the truck is glued to the road. The auto four wheel drive combined with the traction control and sensatrack do more to keep you on the road then any skills you may have, especially if you're keeping it in two wheel drive. A small increase in fuel milage is a small price to pay for the Peace of mind I get using this feature.

[fondupot]

read post #19. I added something. You gotta drive for the conditions. There aren't any set standards for using the 4wd system. You gotta know when and when not to use the 4wd.

 

But thinking 4wd makes the truck invincible in any adverse conditions is the wrong mindset.

[rocnrol]

Yeah, you posted it while I was writing mine. Driving for the conditions is by far THE best advice hands down. All iam saying is around here the conditions can go from bare and dry to black ice out of nowhere. I was making a trip on the highway one sunny winter day a couple of years ago when out of nowhere I hit a wall of cold and wind, the temperature dropped faster than the readout on the mirror could show, the windows just frosted right over, and the wind just started blowing across the hi way carrying the snow from the field with it

As the snow hit the warm road, it just turned to instant ice! And with the high winds the truck was literally blown sideways across the road on the ice. The truck never missed a beat, stayed straight and in control. No way could have done this if I was in two wheel drive. This was in my 07 GMT 900.

[redwngr]

Both Grade Braking and Hill Descent will cause a message on the DIC:

 

Tow/Haul Grade braking:

Tow/Haul Mode Grade Braking

Tow/Haul Mode Grade Braking is

only enabled while the Tow/Haul

Mode is selected and the vehicle is

not in the Range Selection Mode.

See “Tow/Haul Mode” listed

previously and Manual Mode on

page 9-37. Tow/Haul Mode Grade

Braking assists in maintaining

desired vehicle speeds when driving

on downhill grades by using the

engine and transmission to slow the

vehicle.

in vehicles with a gasoline engine,

to disable or enable Tow/Haul

Grade Braking within the current

ignition key cycle, press and hold

the Tow/Haul button for

five seconds. When the button is

released, the requested mode

change is made. A DIC message is

displayed. See Transmission

Messages on page 5-41.

 

HILL DESCENT:

Hill Descent

Control (HDC)

If equipped, HDC can be used when

driving downhill. It sets and

maintains vehicle speed while

descending a very steep incline in a

forward or reverse gear.

The HDC switch is on the center

stack, below the climate controls.

Press 5 to enable or disable HDC. (5 is the hill descent control button)

Vehicle speed must be below

50 km/h (31 mph).

The HDC light displays on the

instrument cluster when enabled.

HDC can maintain vehicle speeds

between 3 and 22 km/h (2 and

14 mph) on an incline greater than

or equal to a 10% grade. A blinking

HDC light indicates that the system

is actively applying the brakes to

maintain vehicle speed.

When HDC is set, that is the initial

set speed. It can be increased or

decreased by applying the

accelerator or brake pedal. This

adjusted speed becomes the new

set speed.

HDC will remain enabled between

22 and 60 km/h (14 and 37 mph),

however vehicle speed cannot be

set or maintained in this range.

It will automatically disable if the

vehicle speed is above 80 km/h

(50 mph) or above 60 km/h

(37 mph) for at least 30 seconds.

5 must be pressed again to

re-enable HDC.

When enabled, if the vehicle is at a

speed above 22 km/h (14 mph) and

less than 60 km/h (37 mph), a DIC

message will display.

[redwngr]

If you have 4x4 with the AUTO mode, it only engages the front axle when it senses wheel slip (rears turning faster than fronts). In regular 4x4, the front is engaged all the time.

 

Either mode can be engaged on the fly.