Its not a momentum thing, its a traction thing. If you were to jack up the front of your h3, place a giant boulder under it so the front tires are off the ground, and try to drive, both front tires would spin because ther is not traction. If you put it in high lock, they will still spin, butn now only as fast as the rear ones. The Scout has a part time transfer case, so when you shift it into 4 hi, it is the same as the H3 being placed in 4 high lock. The point I was trying to make is that sires spin because of a lack of traction, not how the power is being diverted. All four wheels will get the same equal power all of the time. It is the available traction to each tire that determines wether it spins or moves the vehicle.
Two spares the SW is smart, but they still need to be the same size. Letting the air out of the tire will shorten the drive radius, but unless you air down on the street first to find out how much air you need to get the same drive radius as the smaller tire when mounted and fully inflated with weight on it, then you are still putting a bad strain on the drivetrain. 1/4 inch difference is a lot in radius because that translates into a different circumferance which means a different amount of revolutions per mile. You would need to be dead on in the tire pressure of the other 3 tires in order to keep it close enogh to not cause damage.

But hey, its your vehicle. You asked for our advice. Several have suggested that it is a bad idea, but if you want to do it, good luck.

 

I didn't know Shorty had a yellow H3 too..Guess he calls that the Shorterbus

 

Linus, you are 100% correct which is why I put TruTracs front and rear on my Jeep Liberty Renegade (which after 106,000 miles I traded for my new H3). As it has the Adventure Package and e-locker on the rear, looks like I'll be putting a TruTrac on the front to give me true 4-wheel drive when the conditions allow.
As far as locked diffs on ice - the wisdom I have been taught is that truly locking the two rear wheels can lead to side-slipping especially in a turn.
Has anyone put a TruTrac (or torsen-type) locker in the front of their H3?

 

Was you liberty full time 4wd? I don't think you're going to like the auto locker up front with a full time system. On the street, your rear diff will be unlocked, but the front will lock up upon throttle input. So, even though you're driving around in just 4 high, you will have 3 wheel drive. Two up front, and one rear.

And yes, without a "dead" tire to act as an anchor, a locker will cause major side slip on ice without careful throttle control. If no traction can be found then the tires tread design working against the friction will usually result in lateral travel.

 

Good point, I hadn't thought about that. My Liberty was not full-time 4WD. When in 2WD it drove like any other RWD vehicle. When in Full Time 4WD (transfer case proportioning power to front and rear but not "locked") the steering was heavy - like early front-wheel drive cars with a lot of torque steer. I never drove it on pavement in Part Time 4WD (either Hi or Lo) but mand was it great to have all 4 wheels turnin' and churnin' when off-road, especially with 265/75-16 GoodYear MTR's.

I'll have to think about it some more. Do you know what model the front diff might be? My Lib had a D30a (aluminum case - others blew it up, but I never had a problem esp with the TruTrac). Has anyone tried an E-locker up front?
Thanks for the response Fireman.
Paul

 

Check out the visual on the H3 website, go to offroad and look at the twist ditch video. It show how the power is transfered from wheels that have the least resistance to the wheels that have the most. Most 4 wheel drive vehicles will actually do the opposite, thats how I always seem to get stuck in my explorer and my buddys f-150.

 

As of yet, I do not believe anyone makes a locker for the front of the H3 AmStar has one in developement that will be available through your local Hummer dealership, but I do not beileve that is in production yet. This is an upgrade I will consider when it comes out, especially the AmStar one because it will retain the full remaining factory warranty, but I am leary of the idea because of the stories I've heard of people blowing difs. Not knowing the full story of why the others failed, though, my worries could be misplaced.

 

Wait til you get to be my age..you start misplacing a lot of things[&:]

 

Like Linus said, I think Hummer is supposed to make one available through the dealers. But, I have no idea on cost, and can only imagine what it will be. As for others, it takes the aftermarket some time to design and test new units for the latest vehicles. So, my advice would be to just hold off and give them a chance to get them out in the market. At least when they do, you'll know they spent some time going over them, instead of just making it and putting it out there. But your only real option will be something selectable, due to the fulltime 4wd. I have also heard that ARB is on the move to get some things out for the Hummers (H3) including a small suspension lift, that isn't just for show. It's actually through old man emu, who always makes their suspension systems just a couple of inches taller than stock, but with better travel.

I agree, once you have four wheels chewin' up the trail like a fat man cheating on a diet, theres just no way to get used to anything else. It makes wheeling a "point and shoot" affair.. for the most part, of course.