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Discussion Starter · #1 ·
Under what conditions do you want to use 4wd lo? I know very little but was reading how you can pretty easily damage driveline parts.....I put my truck in 4wd lo and drove up a paved road for about 2 miles total,15mph max.....just wanted to make sure everything was working correctly as I've had truck for few monthes and only checked it at time of purchase.I noticed the rearwheel can skip when making a slow turn? I only made two turns,was mostly straight driving...I've since read it's not advisable to use 4wd lo like this? Everything seemed to work as it should,and as I said I took it real easy.....Any advice? Thanks much!!
 

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I don't have a 4wd and there are others that can explain far better then me, but here's what I gather. Never use it while turning on paved or other hard surfaces, only when going straight when you absolutely need to, since on a turn the wheels will move at different rates that causes bind.
 

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My Dak is 2wd, but my GMC is 4wd. However, I've never had occasion to use the low range. here's what a 4wd site has to say about it:

"4-Lo uses shorter gear ratios, hereby keeping the revs high and always in the vehicle’s power band/range. This makes stalling more difficult in 4 Lo. Many people are under the impression that 4-Lo increases the vehicle’s torque, however, it does not increase but only utilizes the existing torque easier and quicker by keeping the vehicle in a higher rev-range and in the highest torque band of the vehicle. This ensures the vehicle’s power is readily available."

So I guess if you had to hitch up to something extremely heavy, like industrial farm equipment or well equipment, & you were off the paved road (like maybe on a gravel road or in a field) lo might be applicable; I believe that lo is pretty industrial. Maybe if the apocalypse happened & you were driving through a tar pit trying to escape & your engine was bogging & having a tough time keeping the wheels moving Lo would be the way to go.

As far as running your truck in 4wd Hi OR Lo on dry roads, I wouldn't do that at all.
 

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It seems that you are not the only one who has asked this question:


I would also say that for 4wd lo to be effective, you would have to have some tires with some radically aggressive tread that hooked up real good no matter what the conditions of the earth you were on was. Otherwise, I would think that no matter what your gear ratio was, when the going got so tough you needed four-lo, tires would just spin.
 

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Heres the low down on how to use the system. Hi range or Lo range, 4wd is to only be used when there's low traction. For example, you can use 4wd on ice as ice is a very low traction surface, but not on wet pavement. Though wet pavement can be slippery, overall it has much greater traction than ice.

4wd Lo, compounds your existing transmission gears. Torque IS multiplied by the ratio of the Low range gear. In this case, the Low range gear ratio in your transfer case is 2.72:1
Lo range is suitable for difficult terrain where more torque is needed to help overcome obstacles, such as soft sand, deep mud, steep climbs or pulling stumps, pulling stuck vehicles, etc.

You use Hi range on slippery surfaces, Lo range when the terrain is difficult. Your transfer case has shift-on-the-fly capability, which means you can shift while rolling from 2wd to 4 Hi and back, (up to 25mph) however there are several do's and don'ts. You can shift between 2wd and 4 Hi when the road ahead is known to be slick, then shift back as soon as you clear the slippery spot. Or you could shift into 4 Hi at a red light during a heavy rain, so that you do not spin once the light turns green, then flip it back to 2wd once you are beyond the light. But as mentioned, do not leave the transfer case in 4wd even on wet roads because there is enough traction to develop drivetrain bind. Never shift into 4 Hi if the tires are spinning in 2wd. For example, if you spin the tires while in 2wd, a shift into 4 Hi will result in scattering parts. There is no shift-on-the-fly capability between 2wd and 4 Lo. To shift into and out of 4 Lo, you must be fully stopped. In some instances you may develop a small amount of drivetrain bind if you were driving on hard packed dirt in 4 Lo. In that case, you may need to back up a few feet to relieve the bind or spin the tires in reverse.

The 4wd system is very different then an All Wheel Drive system. AWD is intended for on road use, a true 4wd system is intended for off road use. A shift into 4wd engages the front axle and both will turn at the exact same rate, no matter what. In an AWD system, there is a differential -or an electro-mechanical clutch to disengage, to allow for variances in axle rates. Since in a 4wd system both axles are turning at the same rate, anytime an axle is forced to turn at a different rate to the other, it creates damaging bind in the entire drivetrain. This is why the system is to be used either on difficult terrain or slippery conditions. These surfaces will allow the bind to be relieved thru slight tire slip which can only occur on loose or slippery terrain. If the system is used for several miles, on a high traction surface, bind develops and result in catastrophic damage. The damage can be as minor as blowing a u-joint or an axle CV joint, to major damage, like cracked front differential, grenaded transfer case, snapped driveshafts, or twisted axle shafts.

Ed
 
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Never shift into 4 Hi if the tires are spinning in 2wd. For example, if you spin the tires while in 2wd, a shift into 4 Hi will result in scattering parts.

There is no shift-on-the-fly capability between 2wd and 4 Lo. To shift into and out of 4 Lo, you must be fully stopped.
Technically speaking, I guess mine is 3wd. At least when I really need it it's only three wheels. (I do have limited-slip in back.)
As far as shifting into 4 from 2, when the tires are spinning, I did that once (years & years ago) & I guess I got lucky--I only blew the fuse for the system.
To get mine into 4 Lo (which I haven't done often at all) not only do I have to be stopped, I have to be in neutral.
 

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Discussion Starter · #7 · (Edited)
Thanks everybody, I learned alot..Thanks RXT for all the details,I like details....that's where the answers are! Lol.I will not drive 4wd lo on dry road or make turns again!! Only very low traction situations m m which I doubt I'll encounter.I did realize ratios etc come into play,inner wheel turns less than outer wheel etc.I just didnt realize it could cause damage so quickly.I dont think I damaged anything,everything seems to be working fine.To release any bound up gear tension you can drive in reverse while still in 4wd hi or lo? I looked on the glove box and found I hav 3.55 rear gears and a regular diff I believe? I read to look for "anti spin" rear diff? I don't see that listed anywhere. It just says corporate 9.25..?I can never remember what else they are called...lol....will an anti spin rear diff avoid all the binding issues described above? Thanks again!!
 

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Bind up damage can happen quickly or cumulatively, depending on which part fails first.

Yes, to release bind, you can drive in reverse. (you don't need to travel very far, a few feet should be enough) Driving in reverse will relieve bind, and it will work for either Hi or Lo range, but it's more likely to do this for Lo range. This is not something you have to do each time, only when the transfer case is having difficulty shifting out of 4wd.

Anti-Spin means there's a limited slip differential. There are different names for them. Previously, Chrysler called them Sure-Grip. GM called them Posi or Positraction and that name is very popular and typically generically applied to all limited slips. Bind will still occur with a limited slip

Ed
 

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Discussion Starter · #9 · (Edited)
Thanks again! Another question if I may? LOL does a limited slip differential eliminate bind? I assume it is for giving better traction but was wondering if it also eliminates binding tension?.... never mine! LOL I see at the end of your statement you say limited-slip will still have bind....:).... I found a bit of rust where the wheel well attaches to the side wall of the bed. One side of the truck is going to need a patch the other side just has a very tiny bit starting there. A little sandpaper and rust reformer and then a bit of silicone on top is what I was thinking? Thanks again
 

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The limited slip really doesn't have anything to due with the transfer case or 4wd; it spins both tires on an axle (instead of just the one) when you get into a situation where you lose traction. It is not true posi-traction, as it will compensate for going around curves, so the inside tire will not turn as fast as the outside tire. In a true posi-traction, both tires turned at the same speed regardless of corners or no corners. I think.
 

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Thanks again! Another question if I may? LOL does a limited slip differential eliminate bind? I assume it is for giving better traction but was wondering if it also eliminates binding tension?.... never mine! LOL I see at the end of your statement you say limited-slip will still have bind....:)....
Just to clarify a bit more. Yes Limited Slip provides better traction. There are a few different types of limited slips, but the one which is common as OEM is the clutch pack design. Heres a video explaining it's operation;

As mentioned, bind will still occur with a limited slip. The best way to avoid bind is to avoid using 4wd on hard surfaces, any surface that allows a tire to slip just a bit, will reduce the possibility of bind.

I found a bit of rust where the wheel well attaches to the side wall of the bed. One side of the truck is going to need a patch the other side just has a very tiny bit starting there. A little sandpaper and rust reformer and then a bit of silicone on top is what I was thinking? Thanks again
You may want to make another post concerning this in the appropriate forum topic, that way you can get the right responses and it's not lost here. But I will respond to one point. I would discourage the use of silicone in your repair because silicone can cause rust to form.

....... It is not true posi-traction, as it will compensate for going around curves, so the inside tire will not turn as fast as the outside tire. In a true posi-traction, both tires turned at the same speed regardless of corners or no corners. I think.
Posi-traction is nothing more than a clutch type limited slip differential. All diffs are designed to allow the tires to turn at different rates when cornering. The only types of differentials that turn both tires at the same rate regardless of corners, is a spool (Which is really not a differential) or a selectable locker, such as an E-locker or ARB air locker when in the locked mode. These units will provide the absolute best traction possible exceeding the capabilities of a Limited Slip in extreme off road environments. But they can be dangerous for someone not familiar with their use and should not be used on the road, while in the locked mode.

Ed
 
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