4WD Question
#11
01-14-2010, 10:51 AM
If you have a base model (no adventure or off road suspension package) then you have open diff's in both ends. If you have an adventure package or off road suspension package that is an 08 or older you will have a electronically locking rear differential, if it is an 09 or newer it will have both front and rear locking diffs. If you have locking diffs there will be a button on the right side of the 4wd control panel that engages the locker, you will have two locking buttons there if you have two lockers.
If you don't have diff locks then there will only be one small button on the far right side of the 4wd control panel, it is for turning off the stability control system.
On the 08 and older ones that only have the rear locker, the far right small button is for turning off the stability system, the second from right button is for the rear locker.
On the 09+ models one far right button runs one locker and the next one runs the other locker, the stability control switch is moved to the lower part of the dash in one of the holes that would be used for aux lights, next to the heater controls.
#12
01-15-2010, 03:46 AM
transfer case mystery
it would seem that the tc is like a "rearend" turned sideways supplying power to sets of wheels.
if so and no lock anywhere then if one or both front wheels spin all power would go to front???, or vice versa.
or if one wheel front or rear spins they get all power, like the old days, one wheel slipping???
even in lock mode both front and rear get power but if one wheel f or r slips we dont go!!
im getting curious-er about how 4wd works without locking, and even with locking tc but not diffs??
if you lift the rear, i dont see the front going anywhere at any rpm unless in lock mode??
more info,,,
tom
if so and no lock anywhere then if one or both front wheels spin all power would go to front???, or vice versa.
or if one wheel front or rear spins they get all power, like the old days, one wheel slipping???
even in lock mode both front and rear get power but if one wheel f or r slips we dont go!!
im getting curious-er about how 4wd works without locking, and even with locking tc but not diffs??
if you lift the rear, i dont see the front going anywhere at any rpm unless in lock mode??
more info,,,
tom
Last edited by drtom; 01-15-2010 at 09:00 AM.
#13
01-15-2010, 09:07 AM
it would seem that the tc is like a "rearend" turned sideways supplying power to sets of wheels.
Very close; The tc unless you switch it to neutral is always supplying power to the rear through a direct connection. I have not inspected the inner workings of this tc but I know that it does this.
if so and no lock anywhere then if one or both front wheels spin all power would go to front???, or vice versa.
Therefore this statement is incorrect in reality, in open differential theory it would be correct but the tc is operating mechanically different than an open diff. which flows power to the path of least resistance.
or if one wheel front or rear spins they get all power, like the old days, one wheel slipping???
Not really In the H3 the rear gets power all the time, the front is driven by some type of clutch system in the tc that allows slipage front to rear in the normal drive mode thereby preventing drivetrain bind on the pavement in this mode. The rear will always spin if enough power is applied in this drive mode but the front if it has enough traction can overcome the clutch system in the tc and not spin with the rear
even in lock mode both front and rear get power but if one wheel f or r slips we dont go!!
No in lock mode the tc now locks the front drive to the rear drive and it will spin one front and one rear at the same rpm (given there is not a locking diff engaged which would make both tires on a given axle spin along with the one (or both in a second locking diff situation) on the other axle). So in the tc lock modes if you have two tires in front or two in rear with enough traction the vehical will go even if the other end is off the ground. This could happen with only one tire on the ground and a locking diff in the end with the tire on the ground.
im getting curious-er about how 4wd works without locking, and even with locking tc but not diffs??
if you lift the rear, i dont see the front going anywhere at ny rpm unless in lock mode??
It will move in this mode only because if the rear tries to spin fast enough whatever is allowing the clutch to slip in the tc will eventually be overcome by the friction and make the front pull.
more info,,,
This type of drive system has really been around since at least some time in the 70's. Most 4wd's weren't that way but some could be had that way, I remember that gm built what they called full time 4wd's and jeep made the quadratrac and both were this kind of drive system.
In conclusion we have normal drive mode 4hi which applies power to the rear all the time and through some kind of clutching system applies some power to the front also.
4lock hi or low which applies a 50/50 split front to rear, will always cause at least one front and one rear to spin.
4lock hi or low, plus diff locked (engaged separately by operator if equiped) In this mode both wheels on the locked axle plus one on the unlocked axle will all spin the same rpm. If both axle diffs are locked and the tc is in lock mode we now have true 4wd and all four tires will spin the same rpm. I would like to point out again that diff locks are only in vehicals with the adventure or off road suspension pack. and were available rear only pre 09 models, after 09 they would come with front and rear. tom
Very close; The tc unless you switch it to neutral is always supplying power to the rear through a direct connection. I have not inspected the inner workings of this tc but I know that it does this.
if so and no lock anywhere then if one or both front wheels spin all power would go to front???, or vice versa.
Therefore this statement is incorrect in reality, in open differential theory it would be correct but the tc is operating mechanically different than an open diff. which flows power to the path of least resistance.
or if one wheel front or rear spins they get all power, like the old days, one wheel slipping???
Not really In the H3 the rear gets power all the time, the front is driven by some type of clutch system in the tc that allows slipage front to rear in the normal drive mode thereby preventing drivetrain bind on the pavement in this mode. The rear will always spin if enough power is applied in this drive mode but the front if it has enough traction can overcome the clutch system in the tc and not spin with the rear
even in lock mode both front and rear get power but if one wheel f or r slips we dont go!!
No in lock mode the tc now locks the front drive to the rear drive and it will spin one front and one rear at the same rpm (given there is not a locking diff engaged which would make both tires on a given axle spin along with the one (or both in a second locking diff situation) on the other axle). So in the tc lock modes if you have two tires in front or two in rear with enough traction the vehical will go even if the other end is off the ground. This could happen with only one tire on the ground and a locking diff in the end with the tire on the ground.
im getting curious-er about how 4wd works without locking, and even with locking tc but not diffs??
if you lift the rear, i dont see the front going anywhere at ny rpm unless in lock mode??
It will move in this mode only because if the rear tries to spin fast enough whatever is allowing the clutch to slip in the tc will eventually be overcome by the friction and make the front pull.
more info,,,
This type of drive system has really been around since at least some time in the 70's. Most 4wd's weren't that way but some could be had that way, I remember that gm built what they called full time 4wd's and jeep made the quadratrac and both were this kind of drive system.
In conclusion we have normal drive mode 4hi which applies power to the rear all the time and through some kind of clutching system applies some power to the front also.
4lock hi or low which applies a 50/50 split front to rear, will always cause at least one front and one rear to spin.
4lock hi or low, plus diff locked (engaged separately by operator if equiped) In this mode both wheels on the locked axle plus one on the unlocked axle will all spin the same rpm. If both axle diffs are locked and the tc is in lock mode we now have true 4wd and all four tires will spin the same rpm. I would like to point out again that diff locks are only in vehicals with the adventure or off road suspension pack. and were available rear only pre 09 models, after 09 they would come with front and rear. tom
Last edited by 4DIGR; 01-15-2010 at 09:10 AM.
#14
01-16-2010, 11:39 AM
"front is driven by some type of clutch system"
ah haa!
the secret i could not see or even imagine!!
i should have started with,,,WOW!
a lot more going on than i thot
2 locking diffs ,fun to mess with
thanks for "saveable" info
tom
ah haa!
the secret i could not see or even imagine!!
i should have started with,,,WOW!
a lot more going on than i thot
2 locking diffs ,fun to mess with
thanks for "saveable" info
tom
#15
01-17-2010, 10:35 AM
Interesting discussion. I gotta say I've been confused by this, as well.
Not to go off on a tangent, but what's the difference between 4WD and AWD? Or is 'AWD' just a marketing thing?
Not to go off on a tangent, but what's the difference between 4WD and AWD? Or is 'AWD' just a marketing thing?
#16
01-17-2010, 03:16 PM
4WD has always been used to indicate vehicals that had a two speed (4hi/4low) transfer case. AWD has generally been used to indicate vehicals that have driven power delivered to all four wheels, generally no low range in the t-case, no operator control of the drive mode, and generally no lock mechanism in the t-case.
That said the H3 and I believe some others (Escalade, some Tahoe, and the list probably goes on and on nowadays) seem to have AWD and yet are 4WD by the above definition.
Some examples of vehicals that are awd are alot of minivans, some Audi cars, Chrysler and Ford both make AWD sedans, some BMW cars, alot of Subarus, etc.
#17
01-17-2010, 04:45 PM
So AWD is simply 4WD with some default 'one size fits all' configuration? My wife's Chevy Express van has AWD and it's a joy to drive in the snow compared to the G20 and Ford Econoline she had before that. With that and my H3 the only cars in the family, I've considered retiring the snow blower 
#18
01-18-2010, 01:20 AM
Senior Member
Join Date: Dec 2009
Location: UK (formerly Chavlamabad, Arabia)
Posts: 110
I've always assumed that AWD and 4wD are the same thing (at least on a vehicle with 4 wheels).
Similarly sometimes I see 4x4 or 4by4 - I don't believe any of these refer to specific types of 4 wheel drive and so can be used interchangeably.
Similarly sometimes I see 4x4 or 4by4 - I don't believe any of these refer to specific types of 4 wheel drive and so can be used interchangeably.
