2H or A4WD what should you drive in?

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
n0kfb said:
...both wheels are powered....

HARDTRAILZ said:
... they hardly ever are both powered.

Just to add my 2c to hopefully clarify the situation. An open diff, by definition, splits power equally between the two sides. The TORQUE (torque is power) sent to the left is the same sent to the right. Torque is like water in a hose - if there's a cut, it tends to flow out the leak rather than go to the nozzle at the end and do what you want it to. If it's a small leak, you might still get some decent flow out the nozzle as well.

A slipping tire is like a leaky hose. Torque leaks out the spinning tire, and no MORE than that amount of torque is going to be available at the tire with traction (the nozzle). Just like pressure equalizes in a plumbing system, torque equalizes in a differential drivetrain.

Don't confuse a tire's observed RPM with power. It takes very little torque (power) to get a tire in the air spinning freely.

One way to prove that is to get on a tippy situation with one front wheel in the air, spinning freely. Then take a ratchet strap and strap that tire to your rock sliders and prevent it from rotating. The opposite front tire with traction will suddenly be able to get some torque out of the differential, and may be able to pull you up the trail. Some times you can get part of the same effect with left foot braking, applying power and braking at the same time, and the brake-induced torque on the spinning tire gets applied to the non-spinning tire and progress is possible. Torque-controlled vehicles with automatically applied brakes might thwart this tactic. :wink:
 

bleu7

Member
Mar 27, 2012
36
the roadie said:
Just to add my 2c to hopefully clarify the situation....:


could you clarify one thing from earlier to me, you stated that Trailblazers should not crow-hop in AUTO mode, unless there is an issue with the transfer case correct?

mine has been crow-hopping whenever i put it into auto mode, since replacing the front diff, input? :confused::confused:

it drives fine in 2Hi
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
Not much to clarify. They should not crow hop in A4WD mode. Not enough torque is being transferred forward to cause this to happen. You have a problem in your transfer case, or more rarely, the front diff. Check it out, or pay to have it checked out. It's probably not a DIY cheap fix.
 

LBB

Member
Apr 5, 2012
53
the roadie said:
please everybody use the correct term A4WD

Ok, what does this term A4WD stands for?

As nobody else in the vehicle universe uses it.

MAN_10to_gl.JPG



Even this one here uses 4WD or AWD.
4WD would be the back two axels only while AWD is everything it has.
And yes it has 7 differential locks, in case you wonder.
 

MDBT

Member
Jan 26, 2012
223
It refers to the automatic engagement of a part time 4wd system, as opposed to moving a lever or pushing a button or turning a knob yourself the computer senses slip and engages the part time 4wd system.

AWD is a system that can never be manually put into 2WD, and in the case of the GMT360 uses a different transfer case.
 

n0kfb

Member
Dec 8, 2011
104
LBB said:
Ok, what does this term A4WD stands for?

As nobody else in the vehicle universe uses it.

>snip<

A4WD = Automatic 4 Wheel Drive.

Per my owners manual, you can shift to and use this mode at any speed on any surface.

-- Dan Meyer :coffee:
 

LBB

Member
Apr 5, 2012
53
MDBT said:
AWD is a system that can never be manually put into 2WD, and in the case of the GMT360 uses a different transfer case.

How lucky I have only 2WD.

But if I had AWD I would with that I have a nice 30/70 or 50/50 or something like this. Even 70/30 would be nice.
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
n0kfb said:
Per my owners manual, you can shift to and use this mode at any speed on any surface.
True, but I remember a couple of reports of early transfer case death from folks who ran around 100% of the time in A4WD mode when the details were discussed. My thought is that you *may* use it at any speed on any surface, but unnecessary use has risks the designers didn't anticipate. It also makes more parts spin then 2WD mode, which increases wear and reduces fuel economy.
 

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