RE: which wheels drive in forward mode?
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RE: which wheels drive in forward mode? - 10/22/2006 11:16:41 AM
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Greenblade
Posts: 649
Joined: 3/19/2006
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quote:
ORIGINAL: shortbus
i assume the H2 has the same type of drive system as the H3. i had all 4 tires barking on the slickrock in moab, and only the rear has a locker. maybe the bus really is retarded, but it had power to both front wheels at the same time . . . and i only had one spare, for whatever that's worth . . . .
Many similar experiences. All 4 tires spin, even if you don't lock the rear diff at all, and even if its in 4-hi-open.
My dealer once described it to me as "one front wheel driven, and the opposite rear wheel is driven", as mentioned above, but i haven't seen that.
Easy way to test that might be to put the truck on a lift and "drive", just watch what happens to the wheels. I've wanted to do that for a while.
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[quote=hummbob]but these days my idea of ROUGHING IT is when there is NO MINT on the Pillow at the Hotel!![/quote]
[quote=ZYNE]I could live with that but a Hotel without room service ... my gawd what is this world coming to?!?[/quote]
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RE: which wheels drive in forward mode? - 10/22/2006 2:17:00 PM
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Fireman
Posts: 514
Joined: 7/16/2006
From: Home of the Alamo
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quote:
ORIGINAL: HummerMike
My reccomendation to anyone that is going into the snow season is to go out to a large parking lot or somewhere where you wont crash into someone/something as soon as you get a decent snowfall or some ice and play around with the different options. It's better to be prepared and know how your vehicle is going to react when you get out into a real situation.
Mike
That's good advice. It's always best to try it out for yourself, and see what works best for you, or what feels best to you. Chances are it may actually be different for different people. As for myself, with the rare, if ever, snowfall we see.. more than likely I'd have to put it in 4wd hi-lock and hope for the best.
Also, getting back to the more than one spare subject. I mentioned carrying a 12v compressor. many of them are very pricey, but for anyone interested, here is a very good unit that will serve most people very well. They were hard to find for a while, with many off roaders buying them up .. but I believe they are back out again, although the price has gone back up a bit. This is a link to a "home test" done on the one I carry.
compressor
I think the price went back up towards the 50.00 mark, but I'm not sure. I bought two when they were still going for 24.00, one I gave to a buddy for a Christmas gift. Anyway, carrying something like this and a trail kit, flat fixer, is probably much easier, and takes up less space etc. Like I said before, if you get a flat, plug it and fill it and run it on the trail. When you are ready to hit the road again, then swap the spare onto the "flat". That way there isn't the danger of a blow out, and when you are home, you can take the tire to a tire shop and have it checked and perhaps repaired better. The compressor is also good for letting you air down a bit for better traction, and then top off the tires for the trip home. If you want to go one better, I carry a small air tank, that I fill with my home compressor, and use it as much as I can. If I use that all up, then I resort to the small compressor.
I just thought I'd post it for anyone who's interested.
_____________________________
"Hey Misterrr Wilsonnnnn!!!!"
'06 H3 w/ Adventure pkg. (wifes ride)
'97 Chevy Z71 w/ 4" & 33's (daily driver)
'82 Toyota SR5 4WD "stock for now" (other daily driver)
'89 Chevy K5 Blazer (trail-rig) too much to list
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RE: which wheels drive in forward mode? - 10/22/2006 8:10:14 PM
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Linus Gump
Posts: 960
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So here's my two cents in the drivetrain subject. All full time four wheel drive vehicles (or all wheel drive) have a center differential. This diff operates just like the one in the axle, i.e. it allows for a different speed from one side to the other, not a different amount of power. Reguardless of how much power is being sent into it, only half of the power is being sent to either side; no more, no less. On vehicles with a high lock option, such as the Hummers, then essentially you are engaging a locker in the center differential. Now you have no slip between the two sides, just as when you engage a locker in an axle.
To clarify, I will talk about axles, but this all applies to the differential in the transfer case equally. Let's assume you have an open differential and an input of 100 lb/ft of torque and 100 horse power. In a strait line, you have 50 HP and 50 lb/ft going to each tire. If you turn, you still have the same power distribution, but now one side turns faster than the other because it has a farther distance to cover in the same amount of time. Now let's say you put one tire on a slippery surface and the other on a high friction surface. Both tires are still recieving the same 50 HP/50 lb/ft, but the one on the slippery surface is now spinning. It spins because the available traction is less than the power being sent to that tire, and because the traction is less than the other side. The tire with all of the traction is still getting its fair share of power, but can't do anything with it because the power required for it to move the vehicle by itself is unavailable. If you were to compare this to something that only applies power to one tire, like a go cart, then if the tire with power is on a high friction surface, the thing goes, even if the others are on a slippery surface, If that tire is on a slippery surface, then it doesn't go reguardless what the other tires have for traction.
In this scenario, in essance, as far as the components are concerned, all you have done is go around a corner. It doesn't matter which tire has what traction, they still get equal power.
To prove this, find somewhere that you can drive up onto a ramp until you have tires come off the ground, and that you can approach from the other side to get the tires that were previously on the ground in the air. You will get the right rear and left front tire off of the ground going one way, and the left rear and right front off the ground going the other. Either way, once the two tires that are being lifted off the ground see enough of a reduction in traction, they will both spin and you will quit moving. The distance traveled up the ramp will be the same for both sides. The power being sent to each tire is still 1/4 of what the engine is producing, but the two that are spinning aren't contributing their share of the work.
Now, if the vehicle has a locking differential, and you engage it, if the traction available to the two remaining tires is sufficient to move the vehicle, then you will move. If not, then you will have three tires spinning, the two on the axle that is locked, and the one in the air on the unlocked axle. If you have a locking diff in that axle, and you engage it, and the traction available to that tire is sufficient to move the vehicle, the progress continues. If not, then you have all four tire spinning. If you are in high lock or low range, then all four wheels will spin the same speed. If you manage to get in to this situation in 4 high (open) then you may notice a speed differential from front to rear, but both tires on a given axle will spin the same speed, and all four are still recieving the same amount of power as they were when they were all on the ground.
Another way to think about it is: Out of the four points of contact, and possible traction to the ground, 2 wheel drive will gaurantee one tire with the potential to move the vehicle (1 wheel drive). All wheel drive with no locking center diff will ga
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RE: which wheels drive in forward mode? - 10/22/2006 8:22:55 PM
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Linus Gump
Posts: 960
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Oh yeah, as far as the oddball spare tire, unless you plan on driving only in high open, or a 2 wheel drive, you are asking for serious drivetrain damage reguardless where you put it, because the transfer case will try to make both drivelines turn at the same speed, but that short tire will want to turn faster than everything else. It's like it is prepetually driving around in it's own private cirlce while everyone else is driving strait.
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RE: which wheels drive in forward mode? - 10/23/2006 3:20:31 AM
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skeeet
Posts: 256
Joined: 2/2/2006
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As to why I carry 2 spares it was because Arizona can have some very, very remote places and the roads, like up to Crown King, have very sharp shale rocks that put holes in your tires that are way too big to be plugged. I found that out in my 96 G. Cherokee with new BFG AT's. No plug kit was going to repair those flats. I figured that if I aired down the 315's and if I had to use the second smaller spare I could get the diameter of the 315's almost the same as the 285 that was pressured up.
Linus Gump - What you say sounds like what I was saying. That a four wheel drive vehicle without a locker or posi is a two drive unless it has a rear locker or posi then it would be a 3 wheel drive. My "All Wheel Drive" Subaru Legecy without a posi or locker is a 2 wheel drive vehicle for sure as was my old Internation Scout "Four Wheel Drive". I remember pulling some logs in the Scout with it engaged in low range, front hubs locked, no posi rear and getting stuck. I pulled the choke handle out so the engine would run without giving it gas and got out of the vehicle and watched as the front right and left rear wheels were spinning. So much for Four Wheel drive. A locking center diff. on the Scout, which it did not have, would make no difference to what wheels would be spinning ,only how much of the engine power they would be getting.
The only factory vehicle that I know of with real four wheel drive is the Rubicon and maybe the H1, the full size Land Cruiser which I think has a factory front/rear posi option and also maybe the Land Rover.
As far as people saying they saw both front wheels of their H3 spinning it was either from the momentum the wheel had from the time it was in contact with the road or from the slight momentum coming from the axle and other internals. No locker or posi then no power to both wheels.
Again, Linus, I think I could get away with a 2" smaller tire if I aired down the 315's and got them to be the same diameter as the 285? I just want to make it to the highway and not walk 40 or 50 miles in 100 degree heat.
ShortBus- If I was in Moab I would not be worried about a flat as the rocks there and off roads are pretty smooth. Shale rocks are like driving on knives and twice as likely to cut your tire when wet. 2" and even 3" holes are not uncommon.
And if both your front wheels were spinning then someone put a posi in the front diff while you were sleeping. Unless it was the momentum of the wheel, tire, axle, etc doing it but not with enough power to really move the H3. We should be going to Moab in a month I'll keep an eye out for a yellow H3.
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RE: which wheels drive in forward mode? - 10/23/2006 7:46:33 AM
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Linus Gump
Posts: 960
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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.
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RE: which wheels drive in forward mode? - 12/6/2006 6:09:42 PM
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CCMDoc
Posts: 219
Joined: 12/5/2006
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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?
_____________________________
Don't save the best for last, the smile for later or the "Thanks" for tomorrow.
Paul
'01 Esprit V8TT - intercooled, chipped and Quaifed
'08 H3 Alpha Off Road-grill lights +1litebar and markers Nav w B/U cam 315s flares flaps and rock protection
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RE: which wheels drive in forward mode? - 12/6/2006 8:16:45 PM
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Fireman
Posts: 514
Joined: 7/16/2006
From: Home of the Alamo
Status: offline
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quote:
ORIGINAL: CCMDoc
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.
_____________________________
"Hey Misterrr Wilsonnnnn!!!!"
'06 H3 w/ Adventure pkg. (wifes ride)
'97 Chevy Z71 w/ 4" & 33's (daily driver)
'82 Toyota SR5 4WD "stock for now" (other daily driver)
'89 Chevy K5 Blazer (trail-rig) too much to list
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RE: which wheels drive in forward mode? - 12/6/2006 8:57:23 PM
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CCMDoc
Posts: 219
Joined: 12/5/2006
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quote:
ORIGINAL: Fireman
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
_____________________________
Don't save the best for last, the smile for later or the "Thanks" for tomorrow.
Paul
'01 Esprit V8TT - intercooled, chipped and Quaifed
'08 H3 Alpha Off Road-grill lights +1litebar and markers Nav w B/U cam 315s flares flaps and rock protection
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RE: which wheels drive in forward mode? - 12/6/2006 10:04:28 PM
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uh60james
Posts: 7
Joined: 12/2/2006
From: Fayetteville, NC
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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.
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RE: which wheels drive in forward mode? - 12/6/2006 10:20:55 PM
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Linus Gump
Posts: 960
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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.
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RE: which wheels drive in forward mode? - 12/7/2006 12:55:29 AM
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Fireman
Posts: 514
Joined: 7/16/2006
From: Home of the Alamo
Status: offline
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quote:
ORIGINAL: CCMDoc
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
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. 
_____________________________
"Hey Misterrr Wilsonnnnn!!!!"
'06 H3 w/ Adventure pkg. (wifes ride)
'97 Chevy Z71 w/ 4" & 33's (daily driver)
'82 Toyota SR5 4WD "stock for now" (other daily driver)
'89 Chevy K5 Blazer (trail-rig) too much to list
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