I'm going to show my ignorance here, probably, but was wondering what is the difference between 4WD High Vs 4WD High Locked? It's always in 4WD High by default, but when would I want to switch it to 4WD High Locked and why? Can someone please explain in Layman's terms??

Thanks!!

 

4 High 60% of power to the rear, 40% to the front. 4 High Lock 50%-50%.

 

He may be right about the power, although I have not heard that.

The lock is your differential locks... Like lets say theres too much pressure one on wheel so the other one is spinning. Well basically that will lock all of your wheels together so all 4 are spinning and you will get more traction. Kind of like Posi Trac..

 

The 4x4 buttons are for the transfer case only there are seperate buttons for locking differentianls.
4hi = 60/40 power split from transfer case to rear/front
4hi lock = 50/50 split
4lo lock = 50/50 split w/ lower gearing
if you have locking diff then that locks the axle so both tires get equal power.
As for using them you can do alot off road in just 4hi but 4hi lock gives better traction & lower gears in 4lo lock give you more torque to climb over stuff.

 

i ASSumed ! that diffs were locked in hi/lo lock because we are warned NOT to use lock on dry pavement.

are locking diffs different??

 

Yes they are different.

 

4hi is normal drive mode. In this mode there is a limited slip coupling of some type in the transfer case that allows the front and rear drivelines to turn at different speeds thus the 60/40 split (that is the gm/hummer spec) although I don't know how accurate that can be. This is necessary in the normal drive mode because on a high traction surface (ie pavement etc.) if the front and rear can't turn at different speeds it can really bind up the drivetrain.

4hilock- when in this mode the transfer case goes into a locked up condition where the front and rear drivelines are not allowed to turn at different speeds hence the 50/50 split of power.

4lowlock- Same as hilock except now the transfer case is adding in a gear reduction which increases the torque being applied to the drivelines. It also reduces the travel speed at the wheels by the same amount as the gear reduction in the transfer case. For a standard base H3 that is 2.64 to 1 reduction, for the adventure/off road package it is 4.0 to 1

The differential locks are a totally different operation and only serve to lock the two wheels on a given axle together and not allow them to turn at different speeds from each other.

If you want to test this out jack both rear tires off the ground and try to drive away in 4hi. The rig won't even try to move until you hit between 10 and 15 mph, now put the transfer case in 4hilock. The rig should try to drive away as soon as it starts to turn a wheel, if it doesn't try to drive away in this mode go to the dealer and tell them you need that plastic shift fork in your t-case fixed

Got all the way to here and realized that I didn't answer the original question. Normaly 4hi is good for most conditions, my rule of thumb is if I start experiencing tire spin it's time to go into a lock mode. Alot of times I'll just leave the t-case in lock if I'm not encountering high traction areas but expect to encounter more low traction areas. Same thing with the diff lock if you've got one.

 

Which is the best for driving on snow and ice?

 

Normal snow/ice driving (slick streets and highway) I usually just run in the normal 4hi drive mode and it does a pretty good job. It is also good if you have intermittent snow and ice especially around town where you're doing alot of sharp turning that will cause your drivetrain to bind if you do it on the pavement in lock mode.

When it comes to secondary roads, deeper snow, or stuff like we do in the desert or mountains in the snow with roads that never see a plow, then I usually go for hi-lock.

Also the diff lock is generally not a good idea on slick surfaces as it contributes alot to causing the rig to slide sideways. I use mine in the snow but only in certain conditions.

 

if the diffs are not lockable , they BOTH? are just regular "rearends" no posi, no nuttin, all the lock is in the tc,just front/rear?

tom