When to use 4WD high?

[Not_Invented_Here_]

Sorry in advance if this doesn't warrant its own thread - I haven't found this specific question asked/answered yet.

I understand how 4H works (mechanically) and this is more about how to use it. In my city, it's very common during a good snow/ice storm for the roads to be "spot treated" - that is, the big main vein city roads may be plowed (and salted yuck) while other side streets and less busy roads are left alone.

Last night I was driving home during one of these snow/ice storms and it occurred to me that for about 80-90% of the drive, the conditions were appropriate for using 4H. But, there was still that 10-20% of the drive where I was driving over loose dry snow and/or some slick ice on visible or semi-visible pavement. I didn't think it would be appropriate to use the 4H (based on what I've read/learned about the system).

I'm curious how others judge conditions for when to use it/not use it and if there's a good rule of thumb beyond "if you can see the pavement, you likely don't want to use 4H"? I definitely needed it for the majority of the drive last night but not the whole thing.

 

[jjvw]

Around town, usually I'll throw the Jeep into 4H after a slip or a spinning start at a stop sign. Then I'll go back into 2H sometime later when I remember that I don't need 4wd anymore.

The 4wd system isn't fragile. Use it when you need it. Run it until you don't.

 

[Not_Invented_Here_]

Thanks for the reply - wasn't entirely sure if it's meant to switch back and forth multiple times over longer trips.

 

[RubiconMike]

The thing to remember about 4H is to only use it on surfaces that have some slip (wet, snow, etc.) not dry pavement. The Jeep TJ transfer case mechanically locks the front and rear differentials together, and does not have any slip like an AWD system with a viscous connection. On dry pavement, this will cause binding on the gears, and can lead to transfer case failure.

 

[jjvw]

The thing to remember about 4H is to only use it on surfaces that have some slip (wet, snow, etc.) not dry pavement. The Jeep TJ transfer case mechanically locks the front and rear differentials together, and does not have any slip like an AWD system with a viscous connection. On dry pavement, this will cause binding on the gears, and can lead to transfer case failure.

If true, then I really ought to have a broken transfer case by now. The problem, if there is one, is that there is the potential to loose traction at higher speeds during a sharper maneuver because (correctly) the front and rear are locked together. Regardless, I can't tell you how many times I have forgotten to switch back to 2H after leaving a trail or snowy city streets, only to discover that I am traveling 75mph in 4H. The transfer case doesn't care.

 

[Not_Invented_Here_]

For sure, so the better question to ask probably would have been how much slip is enough. It's my first Wrangler I'm still learning the in's and out's of driving it in this kind of weather. Thanks for the info.

 

[jjvw]

For sure, so the better question to ask probably would have been how much slip is enough. It's my first Wrangler I'm still learning the in's and out's of driving it in this kind of weather. Thanks for the info.

Don't worry about it. Your tires create more than enough slip to accommodate any transfer case binding that may or may not occur. Your transfer case is not fragile.

 

[Not_Invented_Here_]

Don't worry about it. Your tires create more than enough slip to accommodate any transfer case binding that may or may not occur. Your transfer case is not fragile.

Certainly last night there would have been enough. With my old XJ and this TJ, both auto, I've typically gotten a slow rolling start (~3-5 MPG) - put it in neutral real quick, switch to 4H and then back to drive. Do you do likewise?

It's my understanding you can be cruising at normal road speeds and switch on the fly but for my purposes I've always just done it at the beginning of the trip.

 

[jjvw]

Certainly last night there would have been enough. With my old XJ and this TJ, both auto, I've typically gotten a slow rolling start (~3-5 MPG) - put it in neutral real quick, switch to 4H and then back to drive. Do you do likewise?

It's my understanding you can be cruising at normal road speeds and switch on the fly but for my purposes I've always just done it at the beginning of the trip.

2H-4H is synchronized. There is nothing special to do. However, I will often press the clutch in just to satisfy the mechanical hangups in my head. I have dropped into and out of 4H at highway speeds many times. If it is isn't clear yet, I am quite cavalier in my 4H usage and implementation. I don't think much bout how I get there. 4Low is a little different.

 

[RubiconMike]

@Not_Invented_Here_ Take a few minutes and google when to use 4H. There is lots of information out there.

"You should never travel in four-wheel drive on flat, smooth, dry roads, as it will damage your drivetrain."
https://blog.allstate.com/four-wheel-drive-what-to-use-and-when/

"Don’t destroy your drivetrain.
Driving a part-time 4WD system on dry pavement can break the front axles, shear the differential gears and even break apart the differential case. As soon as you hit dry pavement, shift back into 2WD."
https://www.familyhandyman.com/auto...g-tips-for-how-to-use-4-wheel-drive/view-all/

"It’s important to note that high-range four-wheel drive is not intended to be used on dry surfaces or roads with good traction. Doing so may place undue stress on axles, transfer cases, and other drivetrain components which could lead to damage. It’s important to remember to shift out of 4 HI as soon as road conditions improve"
https://www.gmc.com/gmc-life/how-to/when-to-use-four-wheel-drive

 

[jjvw]

@Not_Invented_Here_ Take a few minutes and google when to use 4H. There is lots of information out there.

"You should never travel in four-wheel drive on flat, smooth, dry roads, as it will damage your drivetrain."
https://blog.allstate.com/four-wheel-drive-what-to-use-and-when/

"Don’t destroy your drivetrain.
Driving a part-time 4WD system on dry pavement can break the front axles, shear the differential gears and even break apart the differential case. As soon as you hit dry pavement, shift back into 2WD."
https://www.familyhandyman.com/auto...g-tips-for-how-to-use-4-wheel-drive/view-all/

"It’s important to note that high-range four-wheel drive is not intended to be used on dry surfaces or roads with good traction. Doing so may place undue stress on axles, transfer cases, and other drivetrain components which could lead to damage. It’s important to remember to shift out of 4 HI as soon as road conditions improve"
https://www.gmc.com/gmc-life/how-to/when-to-use-four-wheel-drive

Find us some evidence of people damaging their NP231 and NP241 transfer cases in the way you describe. Explain how people get around Moab in 4Low and fully locked axles all day long without routinely breaking transfer cases.

 

[RubiconMike]

Find us some evidence of people damaging their NP231 and NP241 transfer cases in the way you describe. Explain how people get around Moab in 4Low and fully locked axles all day long without routinely breaking transfer cases.

I'm not interested in arguing about this, I'm just encouraging the OP to do some research and make up his own mind.

 

[Not_Invented_Here_]

@Not_Invented_Here_ Take a few minutes and google when to use 4H. There is lots of information out there.

"You should never travel in four-wheel drive on flat, smooth, dry roads, as it will damage your drivetrain."
https://blog.allstate.com/four-wheel-drive-what-to-use-and-when/

"Don’t destroy your drivetrain.
Driving a part-time 4WD system on dry pavement can break the front axles, shear the differential gears and even break apart the differential case. As soon as you hit dry pavement, shift back into 2WD."
https://www.familyhandyman.com/auto...g-tips-for-how-to-use-4-wheel-drive/view-all/

"It’s important to note that high-range four-wheel drive is not intended to be used on dry surfaces or roads with good traction. Doing so may place undue stress on axles, transfer cases, and other drivetrain components which could lead to damage. It’s important to remember to shift out of 4 HI as soon as road conditions improve"
https://www.gmc.com/gmc-life/how-to/when-to-use-four-wheel-drive

Appreciate the links - I actually just checked out the familyhandman site earlier. I don't anticipate running to issues that serious with the way I drive but I was curious given the way our city tends to selectively plows roads.

I'd rather be sure than assume and make an ass out of u and me

 

[LukesfirstJeep]

The owners manual has good information on the usage and limitations of 4WD. One of my previous 4WD vehicles (non jeep), allowed 4WD Hi up to 50 MPH.

 

[JDS123]

Find us some evidence of people damaging their NP231 and NP241 transfer cases in the way you describe. Explain how people get around Moab in 4Low and fully locked axles all day long without routinely breaking transfer cases.

You don't go around in Moab all day long in 4 low (at least not in a short wheelbase TJ). Making tight turns on the slick rock in 4 low is a chore. I had to shift into 2 wheel drive a couple times a day to make a sharp turn. The Jeep will just push forward. There is too much traction for it to slip. Turn the lockers on as well and you're not turning at all. It'll rip the steering wheel right out of your hand.

I have no evidence that transfer cases will blow up if you drive around on the road in 4 wheel drive but intuitively it makes sense why you wouldn't want to do it. I've forgotten to shift back into 2 wheel drive a couple of times as well. But I can immediately tell as soon as I try to take a sharp corner.

 

[Not_Invented_Here_]

2H-4H is synchronized. There is nothing special to do. However, I will often press the clutch in just to satisfy the mechanical hangups in my head. I have dropped into and out of 4H at highway speeds many times. If it is isn't clear yet, I am quite cavalier in my 4H usage and implementation. I don't think much bout how I get there. 4Low is a little different.

Ha for sure - I drove my XJ ages ago and had since become spoiled driving the new Cherokees with Active Drive. There's not a ton to think about with those systems besides driving carefully.

 

[Not_Invented_Here_]

I'm not interested in arguing about this, I'm just encouraging the OP to do some research and make up his own mind.

Yeah no worries, not looking to start a debate here ha. The scope of my question is really limited to just this personal use situation. I read Jerry's more cautionary posts about pavement use and then went down that rabbit hole.

My Jeep is almost entirely stock and is intended primarily for DD'ing - the most off road action it's going to see will be light trails, camping/fishing. I understand how the system works but I don't have that situational experience driving in inclement weather yet so I like to get input from others.

 

[Kathy]

Here is an explanation that Jerry shared that made sense to me.

 

[98TxTJ]

Last night I was driving home during one of these snow/ice storms and it occurred to me that for about 80-90% of the drive, the conditions were appropriate for using 4H. But, there was still that 10-20% of the drive where I was driving over loose dry snow and/or some slick ice on visible or semi-visible pavement.

I sounds to me like you had plenty of slip potential for 100% of the drive.

I use 4H in the rain on all my 4WD vehicles. With it engaged, if the tires don't shudder when you turn, it's slick enough for it.

 

[KimsJeep]

I sounds to me like you had plenty of slip potential for 100% of the drive.

I use 4H in the rain on all my 4WD vehicles. With it engaged, if the tires don't shudder when you turn, it's slick enough for it.

I am very new to 4x4's so I was actually going to ask that question, about rain and using the 4 hi. I was curious if it would give me better traction during a rain storm or should I just stick to 2H? I drive freeway part of the way to work, then down a city street the rest of the way. I wasn't planning on using it in a light rain, but if we had a down pour, I was thinking it may help to be in 4H?

By the way, my used Jeep didn't come with an owners manual, need to find one.