JK 4x4 hiway driving

DuxJeep · Unread post by **DuxJeep** » Wed Jan 30, 2019 11:03 am

Just slid across three lanes in NH on some black ice but recovered before anything bad happened.

My question is does anyone know limitations of driving in 4x4 on hiway? I know there are speed restrictions but with 4” of lift and 37s I don’t want to push the limits and few remaining stock components. Appreciate the feedback!

Hoodoo Man · Unread post by **Hoodoo Man** » Wed Jan 30, 2019 11:27 am

If you check the owners manual 4x4 high shouldn't be used above 35mph or so. Might be a bit higher but you definitely don't want to be at 65mph in 4H.

honestly best advice is keep speeds below the posted speed limit when its snowy out and don't be the fool in the ditch that rolled their Jeep. It boggles my mind seeing (mainly f150s and the like) bombing down the highway at 70 while there are two tracks in the road and snow everywhere else, sure you can get up to that speed but good luck with an emergency stop.

Glad your OK!

Frank · Unread post by **Frank** » Wed Jan 30, 2019 3:19 pm

How can that be that 4wd in high is limited to 35 mph ? Its the same ratio as 2wd so whats changed . The T-Case should handle it , Is this a JK thing ? FjR68

Hoodoo Man · Unread post by **Hoodoo Man** » Wed Jan 30, 2019 3:36 pm

OK it seems the JK can go about 50 mph in 4hi I've always heard its not recommended to use 4h on dry pavement or high speeds..

the quote below is from Jerry Bransford who I've seen on Jeep forum and else where and seems to be very knowledgeable. Its in regards to a TJ but the same would apply for a JK or JKU essentially...

It's not so much a strength issue as it sometimes could be a handling issue. First, the TJ's 4x4 system is a "part-time" 4x4 system... i.e. it is not designed to be used full-time on the streets. How it works is the transfer case mechanically locks the front & rear driveshafts together and thus the axles are mechanically locked together so they are forced to turn at exactly the same speed/rpm. However, the front axle needs to turn faster during turns since the front tires have to rotate faster than the rear tires do during a turn. Even on a slight highway curve, not just hard 90 degree turns. That causes drivetrain "wind-up" by the front driveshaft trying to rotate faster than the rear driveshaft is and the transfer case is caught in the middle.

That isn't actually known to cause damage, the transfer case is stronger than that. If it wasn't we'd have Wranglers & other trucks found on the side of the road with broken transfer cases from all of the idiots who know no better and like to drive around in 4x4 even when not needed. The real problem is if you get into a varying traction situation, like patches of snow, ice, or even dirt while driving on the highway, that bind (wind-up) could suddenly release itself if one of the tires hits that low traction area and suddenly spins or slips to release the binding/wind-up. That could conceivably cause a spin-out, slide, etc. in some conditions.

The way full-time 4x4 systems or all-wheel drive systems can be driven in 4x4 full-time is that their transfer cases also have a differential inside (like is inside of our axles) that allows for differentiation between the front and rear axles which means wind-up/binding between the axles does not occur.

So the long and the short of it is driving a Wrangler in 4x4 on a high-traction paved surface is not likely to break anything, but it can at least cause compromised handling, jerky steering, etc. from drivetrain wind-up/binding between the front & rear axles. And it certainly isn't good for the transfer case for it to be the center of this binding problem

ImNotCassie · Unread post by **ImNotCassie** » Thu Jan 31, 2019 8:16 am

DuxJeep wrote:Just slid across three lanes in NH on some black ice but recovered before anything bad happened.

My question is does anyone know limitations of driving in 4x4 on hiway? I know there are speed restrictions but with 4” of lift and 37s I don’t want to push the limits and few remaining stock components. Appreciate the feedback!

Are you new to New England? Most of us cross three lanes on a daily basis ... on purpose.

Frank · Unread post by **Frank** » Thu Jan 31, 2019 8:50 am

I get that Jeff . 4X4 has always had warnings about dry surface operation . Im just so used to manual hubs and one piece axles . Ive never been spoiled enough to have to worry about that

. OldSkool Fool ! FjR68

pirahnah3 · Unread post by **pirahnah3** » Thu Jan 31, 2019 7:18 pm

I want to go to Jeffs quote for just a moment on this one....

So lets look at the concept of "wind up" in relation to driving on pavement. Doesnt this happen to the rear axle no matter if the pavement is wet or dry? If they are considering a turn does the rear of the vehicle not also turn? doesnt this then cause the same problem they are trying to avoid having? Im no expert but it just seems like the logic is a bit off to me. I can see it as far as steering goes as that directly effects the front wheels but the science would state that the rear axle does the same thing and would be more likely to skip as you make the turn rather than jerk the wheel.

BlackNBlue-ISH · Fri Feb 01, 2019 12:17 am

pirahnah3 wrote:I want to go to Jeffs quote for just a moment on this one....

So lets look at the concept of "wind up" in relation to driving on pavement. Doesnt this happen to the rear axle no matter if the pavement is wet or dry? If they are considering a turn does the rear of the vehicle not also turn? doesnt this then cause the same problem they are trying to avoid having? Im no expert but it just seems like the logic is a bit off to me. I can see it as far as steering goes as that directly effects the front wheels but the science would state that the rear axle does the same thing and would be more likely to skip as you make the turn rather than jerk the wheel.

No, because on street vehicles, the rear axle is an open differential, limited slip or automatically locking. These all allow for the inside wheel to turn different then the outside without the binding spoken about above.

In other words, our jeeps have 3 differentials. One on the end of the transmission that splits power from front to rear, and one in each axle splitting left to right. The transfer case is the differential front to rear and in a true 4x4 vehicle acts like a locker. When engaged it splits the power 50/50. So when the jeep turns, the front axle actually travels further then rear. This 50/50 split doesn’t allow for the front axle to spin a different speed then the rear, so it binds and causes the herky jerky characteristics noted above. The rear axle acts the same, but splits the power left to right.

It really helps to understand how a differential works. I watched this video a number of years ago (not in the 30’s when it came out) and it helped a ton.

[youtube] [/youtube]

DuxJeep · Unread post by **DuxJeep** » Fri Feb 01, 2019 8:20 am

Thanks all! Some good information and great video.

Making the trip to Jay Peak next weekend and hope to not need 4x4, at least until I get to the mountain! And definitely not a newbie to New England or snow driving, just looking to know more about the mechanics and limitation of my rig, the more you know the better...

Thanks for the advice and happy Friday.

pirahnah3 · Unread post by **pirahnah3** » Sat Feb 02, 2019 3:15 pm

Dan, I understand the general operational principle, and the video is certainly a great one with good simple explanations in it. I even think I have seen it before...

Ive looked around a bit and the only time I can find anyone with any decent level of explanation for this being a problem is on sharper (not longer sweeping) corners. Even with those examples it is typically focused on the wheels turning at a different speed which by theory of a non locked differential shouldnt be a major problem. Maybe I am just over complicating this in my head but im just not seeing the massive issue that it is made out to be.

Obviously this is all kind of mute as realistically if its dry pavement do we really need to be in 4wd to begin with? No most likely not, if there is a traction problem that would not be considered a high traction surface such as asphalt pavement or concrete road surfaces with normal tire tread.

Frank · Unread post by **Frank** » Sat Feb 02, 2019 8:53 pm

Jim

I would go out on a limb and say they have to print that cause some idiot would sue and win after they proceeded to kill their whole family cause the shift thingy said 4 wheel drive and we all know that means any kinda terrain and or weather never would you get stuck or loose control . I really think if there was snow cover and you drove at a speed you were comfortable at , there would be no mechanical damage to the Jeeps drive train . The biggest concern would be rock climbing tires have little to no sipes and unless you have a select-able locker wouldnt be happy making tight turns. Lock-em in and hang on ! FjR68

BlackNBlue-ISH · Sat Feb 02, 2019 9:23 pm

I guess the other issue with binding could be in the binding of the ujoints due to phasing. But that’s another story for another day.

Frank · Unread post by **Frank** » Sun Feb 03, 2019 8:25 am

If a u-joint is binding , Id get more grease in her on that other day FjR68

zenfire1 · Unread post by **zenfire1** » Wed Feb 27, 2019 2:48 am

I have the Toyo mt 35". Mudder tire. I found real quick I have to take turns, even lane changes slowly. 4hi helps, but there is a lot of slip. Not a great tire in snow. Starts are great, but stops no- almost creamed an Audi that pulled out in front of me.

Frank · Unread post by **Frank** » Wed Feb 27, 2019 8:41 am

Zen you are not alone in that situation . I have driven over a million miles , yes Im old . Driving Tractor trailer , cars , trucks . They all feel similar in snow. Taking off , say from a light seems to have the same feeling. If one would spin , they all would spin . Driving in anything but freezing rain (Black Ice) is a challenge that can be met using your brain . Ice wins every time . Stopping is the issue most people have trouble with , lack of planning , other persons mistake , sleeping at the wheel. Understanding the term 4-Wheel drive is misleading . Thats what gets most people in trouble. First most 4WD arent 4WD at all , at best they are 3WD . UNLESS you spent money on a locker ! Even factory Limited slip will differentiate while making a turn. A locker wont. Id say most after market aggressive tires dont have sipping . The little squiggly lines inside the bigger block of the tires. Thats one reason they slip on snow. The more sipes on a tire the better its grip overall. With select-able locker you have the option to use or not to use. I would not use them 100% of the time. Auto lockers have issues all the time dry-wet-snow . You just get use to the quirks . With open differentials its only 2 WD at best , one on each axle. Because it says 4WD people drive different we can say that and not offend any of the idiots . If your sliding around just changing lanes , I would have to say , get snow tires on other rims for the winter or your gonna have to change your driving habits . Without bragging That million miles has come over 51 yrs. of driving. The surprise fact is Ive done it with out a chargeable accident , or ticket of any kind. Yes Im surprised at myself every time this comes up. Just saying , I might know a thing or two about driving overall. FjR68

Baystate Jeepers

Baystate Jeepers