4WD Lock versus 4WD low

[salibas007]

When would I use the Lock versus the Low ?

I usually drive in 2wd, unless it's snowing or I'm driving on snow covered roads and I switch it the 4WD Auto.

But when would I use the Low versus the lock ? I assume that the low is used a bit like my ATV's low gear, for when I'm stuck in a ditch somewhere or I'm pulling someone and I need that extra torque in low speed..

But what about the Lock ? Is it basically a 4wd with a permanently locked differential ?

How about the low ? Are the differentials locked as well ?

I read the owners manual, and it's pretty vague in regards to the difference between both options.

 

[loveracing1988]

When would I use the Lock versus the Low ?

I usually drive in 2wd, unless it's snowing or I'm driving on snow covered roads and I switch it the 4WD Auto.

But when would I use the Low versus the lock ? I assume that the low is used a bit like my ATV's low gear, for when I'm stuck in a ditch somewhere or I'm pulling someone and I need that extra torque in low speed..

But what about the Lock ? Is it basically a 4wd with a permanently locked differential ?

How about the low ? Are the differentials locked as well ?

I read the owners manual, and it's pretty vague in regards to the difference between both options.

Your diffs will never be locked unless you install lockers (which there are none availble for the front).
There is no true lock from what I have found out. It will only send power to the front when it detects slippage. If you dont believe me put your truck in 4 low and hold your foot on the brake while you are in the snow. It will sit and spin the rear tires until you press on the accelerator pedal a little, it will then send power to the front axle.
I actually just had a conversation with a borg warner engineer. I guess with the people using their trucks for plowing and such the "on demand" transfer cases are buring up like crazy.
To answer your original question though the only time you would need 4 low would be pulling someone out of a ditch or pulling a stump out of the ground or plowing. 4 lock for the rest.

 

[Bluesmoke91]

subbed. have the same questions

 

[PostalTwo]

i use 4 lock when im in loose traction situations like heavy snow or mud where i want the 4x4 constantly locked in and 4 low for pulling stumps and other things that require the extra torque.

 

[salibas007]

Ok. So the 4x4 lock is basically always in 4x4, where as the 4x4 auto will switch between 2wd & 4wd?

Am I getting this ?

 

[TRCM]

Yes, you're getting it.

It's like this......

2wd - obvious

4wd auto - 4wd when needed, normal 1 to 1 gearing thru the t-case, used for snow, ice, whenever you want

4wd lock - 4wd all the time, normal 1 to 1 gearing thru the t-case, used for snow, ice, whenever you want as long as the traction is limited, limited turning radius

4wd low - 4wd all the time, 2.72 to 1 gearing (almost 3x lower), very loose surfaces, slow maneuvers, when high torque/traction is needed, speed limited due to gearing (possible to over-rev engine), limited turning radius

 

[salibas007]

Owners manual says not to drive in neither low nor lock on dry pavement. Why ?

I understand the low, but why not lock ? Why is auto OK, but not lock ?

If I understand this correctly, auto will switch it to 4x4 when needed, but when it does switch, it's the same as in lock mode.. So why is auto OK but not lock ?

 

[TRCM]

Owners manual says not to drive in neither low nor lock on dry pavement. Why ?

I understand the low, but why not lock ? Why is auto OK, but not lock ?

If I understand this correctly, auto will switch it to 4x4 when needed, but when it does switch, it's the same as in lock mode.. So why is auto OK but not lock ?

Because the front and rear axle ratios aren't identical, and driving on high traction surfaces in lock or low, can cause binding in the drivetrain.

In low range, this binding can become severe enough that if you try to force it with engine rpm, you can break stuff....expensive stuff.

 

[PostalTwo]

4 lock is locked in all the time and auto is not so on dry pavement auto is reall never fully engaged while lock allways is, all it take is front and rear tires to spin at slightly different rates and u have damage done. all that torque has to go somewhere and the weakest link in the system is going to take it and break

 

[PostalTwo]

just trust the manual 4 lock when u know u need it and 4 auto if u think u might

 

[TRCM]

4 lock is locked in all the time and auto is not so on dry pavement auto is reall never fully engaged while lock allways is, all it take is front and rear tires to spin at slightly different rates and u have damage done. all that torque has to go somewhere and the weakest link in the system is going to take it and break

Well, while what you are saying IS correct, it will never happen in a stock truck.

For different spin rates front & rear to break stuff, you'd have to have locking diffs front and rear. In a stock truck with even an LSD in the rear like mine, the differing axle speeds (within reason) will be absorbed by the open diff, or the LSD long before you break anything as a result.

IE: 1 side of the open diff will either spin faster or slower to release the binding. So will the LSD (albeit at a higher load). The big thing & most likely thing to break are the u-joints in the front axle while turning. At sharp turning angles, they can bind & snap easily, especially in low.


Don't forget, in low range, you have almost 3x as much torque being applied, so things like u-joints can break very easily.

 

[DublDee]

That was painful....Lol

Just Kidding...Kinda

 

[TRCM]

Owners manual says not to drive in neither low nor lock on dry pavement. Why ?

I understand the low, but why not lock ? Why is auto OK, but not lock ?

If I understand this correctly, auto will switch it to 4x4 when needed, but when it does switch, it's the same as in lock mode.. So why is auto OK but not lock ?

Auto is only locked in while slippage is present...once the slippage goes away, it unlocks.

4WD lock is ok if the surface is slippery, which is when auto kicks in, but in lock, once the slippery condition goes away, you are still locked, whereas auto disengages.

 

[PostalTwo]

Well, while what you are saying IS correct, it will never happen in a stock truck.

For different spin rates front & rear to break stuff, you'd have to have locking diffs front and rear. In a stock truck with even an LSD in the rear like mine, the differing axle speeds (within reason) will be absorbed by the open diff, or the LSD long before you break anything as a result.

IE: 1 side of the open diff will either spin faster or slower to release the binding. So will the LSD (albeit at a higher load). The big thing & most likely thing to break are the u-joints in the front axle while turning. At sharp turning angles, they can bind & snap easily, especially in low.


Don't forget, in low range, you have almost 3x as much torque being applied, so things like u-joints can break very easily.

while i also agree with what u say in order for the diff action to absorb the torque there has to be slippage in the wheels somewhere dry pavment does not allow eough slippage to combat this. to be clear im talking about difference in speed between front and back not left to right. form what ive seen its the pinion in the tcase that taking the brunt of the force and they fail as a result way too much binding and really no where for it to go at highway speed on dry pavement. before reading the last few stories i would have been in the camp that says it shouldnt hurt but the fact is it does.same a setting a wheel bearing too tight eventually its gonna fail. point is 4 lock is not meant for dry roads peroid if its dry use 4 auto

 

[PostalTwo]

Story: Front diff pinion bearing seized, pinion then twisted off. Then the front drive shaft hit the engine mount bracket and tweaked and split the transmission case. The drive shaft also hit the engine oil pan and made 2 dents on the side of it. The pinion got jammed in the ring gear and cause the front differential case to split. The front differential got so hot from the seized pinion bearing that the fill plug and the wiring harness closest to the front diff melted.

all from using 4 lock on the highway oh and no warr from dodge btw

 

[TRCM]

while i also agree with what u say in order for the diff action to absorb the torque there has to be slippage in the wheels somewhere dry pavment does not allow eough slippage to combat this. to be clear im talking about difference in speed between front and back not left to right. form what ive seen its the pinion in the tcase that taking the brunt of the force and they fail as a result way too much binding and really no where for it to go at highway speed on dry pavement. before reading the last few stories i would have been in the camp that says it shouldnt hurt but the fact is it does.same a setting a wheel bearing too tight eventually its gonna fail. point is 4 lock is not meant for dry roads peroid if its dry use 4 auto

First of all...what pinion in the tcase ?? have had several different models apart, and have yet to see a pinion. A pinion is only needed when the path of power transmission has to turn 90 degrees, as in driveshaft to axle shaft.....the transmission to t-case is linear and only needs a chain or gears to power the front, and the rear power travels straight thru. Even my old NP203 t-case, which was a full-time 4wd t-case with a differential in it didn't have a pinion (the differential was really just a sun gear and planetary setup)..but that's another matter


Again, what you are saying is correct and worse if you have locking diffs.....and will even cause issues if the tire speed diffs front to rear are severe (as in intentional)

What I am saying, is that in a stock truck "slighlty differing tire speeds front to rear" as you say will not do damage unless it is for lengthy periods of driving on high traction surfaces. Like when I pull someone out of a ditch, I use 4wd lock because I do not want 4WD auto trying to engage under such a high load situation. I am on the roadway and high traction...but the length of travel is not enough to do damage. Now, if I forget to take it out of lock, that is another story.

The reason for this is the front & rear gear ratios are almost never the same (ex: 4.10 rear, 4.11 front), and that difference will eventually "stack up" and bind, and it happens even faster in low range due to the additional gearing.

Most of the time, turning will alleviate the binding if the front axle is open or LSD due to the differences in how far the front tires actually travel during a turn (inside tire travels less distance than the outside tire) due to the way an open carrier works when transferring power side to side.

We're saying the same thing, but you make it sound like any driving in lock on a high tracton surface will break things, and that isn't true. It will happen faster with locking diffs and in low range but it isn't an immediate thing even then.

 

[TRCM]

Story: Front diff pinion bearing seized, pinion then twisted off. Then the front drive shaft hit the engine mount bracket and tweaked and split the transmission case. The drive shaft also hit the engine oil pan and made 2 dents on the side of it. The pinion got jammed in the ring gear and cause the front differential case to split. The front differential got so hot from the seized pinion bearing that the fill plug and the wiring harness closest to the front diff melted.

all from using 4 lock on the highway oh and no warr from dodge btw

I have a very hard time believing all that was caused by using 4 lock on the road way. I DO think/know it is a very good excuse for dodge to use to avoid paying for it, or to get out of paying for it because they don't know what happened.

For the pinion bearing to go out like that, you'd have to have the ability to force it sideways enough to gaul the rollers/balls in the bearing causing it to seize, (or a piece of something got in the bearing) and that won't happen from the t-case end.....the u-joint will go before that happens.

I'd say the fluid was low and the pinion bearing seized, starting the issue, or, as I have also seen happen, the front pinion nut comes loose, letting the pinion walk around until it seizes the bearing, and then you have the same issue.

I have driven many different trucks on the highway in 4wd 'lock' as you call it, altho some of them didn't call it 'lock', and I have never had any problems that can be directly attributed to it.

I HAVE had problems that someone could blame on doing that if I didn't know better, like having both front hubs disintegrate on my truck. They came apart because:
1) I had 40" tires on a hub designed for 27" tires
2) the hub design had a groove machined in it for a different application that weakened the casting
3) the bearings on this hub were over 20 yrs old, and I suspect the previous owner never lubed them
4) the bearing design was a known problem


But hey, I could ignore all of that and say it was due to driving in 4 hi on the highway, but I know better, and I knew this could happen when I put the larger tires and lift on the truck.

 

[PostalTwo]

First of all...what pinion in the tcase ?? have had several different models apart, and have yet to see a pinion. A pinion is only needed when the path of power transmission has to turn 90 degrees, as in driveshaft to axle shaft.....the transmission to t-case is linear and only needs a chain or gears to power the front, and the rear power travels straight thru. Even my old NP203 t-case, which was a full-time 4wd t-case with a differential in it didn't have a pinion (the differential was really just a sun gear and planetary setup)..but that's another matter


Again, what you are saying is correct and worse if you have locking diffs.....and will even cause issues if the tire speed diffs front to rear are severe (as in intentional)

What I am saying, is that in a stock truck "slighlty differing tire speeds front to rear" as you say will not do damage unless it is for lengthy periods of driving on high traction surfaces. Like when I pull someone out of a ditch, I use 4wd lock because I do not want 4WD auto trying to engage under such a high load situation. I am on the roadway and high traction...but the length of travel is not enough to do damage. Now, if I forget to take it out of lock, that is another story.

The reason for this is the front & rear gear ratios are almost never the same (ex: 4.10 rear, 4.11 front), and that difference will eventually "stack up" and bind, and it happens even faster in low range due to the additional gearing.

Most of the time, turning will alleviate the binding if the front axle is open or LSD due to the differences in how far the front tires actually travel during a turn (inside tire travels less distance than the outside tire) due to the way an open carrier works when transferring power side to side.

We're saying the same thing, but you make it sound like any driving in lock on a high tracton surface will break things, and that isn't true. It will happen faster with locking diffs and in low range but it isn't an immediate thing even then.

pinion is the input member it doeent have to be a helical cut gear.

i agree that we are basically saying the same thing

i myself also have never seen this in real life experence even though i have used my own 4wd in high lock but i would hate to tell someone its ok to use especially after reading the quoted story. i error on the side of caution when giving advice.

op asked about what situations he\she would use 4 lock \vs auto vs low so for me would be use each where its intended low for high torque lock for loose \slippery surfaces and auto when its a mix or ur not sure. can they get away with lock instead well prob but im not going to suggest it even tho i prob wont hurt but it might .

cheers

 

[TRCM]

pinion is the input member it doeent have to be a helical cut gear.


cheers

Never heard it called that...all my books just call it the input gear


and my original post below on the different t-case positions listed the times to use the different ones

Yes, you're getting it.

It's like this......

2wd - obvious

4wd auto - 4wd when needed, normal 1 to 1 gearing thru the t-case, used for snow, ice, whenever you want

4wd lock - 4wd all the time, normal 1 to 1 gearing thru the t-case, used for snow, ice, whenever you want as long as the traction is limited, limited turning radius

4wd low - 4wd all the time, 2.72 to 1 gearing (almost 3x lower), very loose surfaces, slow maneuvers, when high torque/traction is needed, speed limited due to gearing (possible to over-rev engine), limited turning radius

 

[salibas007]

Ok. So to sum all this up:

Low for when serious torque at low speed is needed (ex: pull someone out if a ditch, or even pull myself out of one)

Auto for when I'm driving on normal roads that are covered in sow and i need better traction, but I don't need constant 4x4

Lock if for when I'm driving on roads where I need full time 4x4 due to road conditions. I guess this isn't for highway driving, unless I'm driving through a blizzard or some major storm. More for off-road driving where I wouldn't want the tranny to switch between 2 & 4 wheels and just want it to stick to 4x4.

Did I get this right?


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