4H Usage Restrictions

[Red Wagon]

Hello All,
I'm one of the "lurkers" here. Hoping to order/purchase late this year/early next year if Jeep can/is willing to build me a manual Overland with a few options that are causing build delays, per a few threads on this forum.

I've never owned a Jeep, so I look to you for education on the 4WD system. The manual is clear about the speed limitation of 4L, "Do not exceed 25mph". Got that, not a problem. That's for true off-roading.

Does anyone have previous Jeep "life experience" related to using 4H at highway speed on wet/slippery roads?
I understand that 4H shouldn't be used (& isn't needed) on dry "hard-surfaced" roads, but what about slippery roads due to some form of moisture on the "hard-surfaced" road?

Reference:
Owners Manual, p. 303
"In the event that additional traction is required, the transfer case 4H and 4L positions can be used to lock the front and rear driveshafts together, forcing the front and rear wheels to rotate at the same speed. The 4H and 4L positions are intended for loose, slippery road surfaces only and not intended for normal driving. Driving in the 4H and 4L positions on hard-surfaced roads will cause increased tire wear and damage to the drive line components."

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[ShadowsPapa]

Prior Jeeps (non-Wrangler, but still Jeeps) and Ford and such - if the tires can slip a bit - you should be ok. If the tires cannot slip, then you'll wind things up, bind, cause stress and wear.
So - judgement call.
The reason you want the wheels to slip when in 4H is because even new tires are imperfect in exact dimension - that's a minor thing, the bigger thing is that when you TURN, even just a little corner, the outer wheels turn MORE, farther than the inside wheels. The outer wheels have to make a larger circle, so they cover more ground. The transfer case locks the front and rear axles together, if the combined travel of the two wheels on either axle is more or less than the combined travel of both wheels on the other axle, you have a bind in the transfer case.
As long as any wheels can slip a bit, it relieves that pressure. Just "wet" shouldn't slip if your tires are decent, so just wet roads I won't use 4H personally - I've had a heck of a time in the past getting the t-case out of 4 at times.
Really if it's just wet you don't need 4H - the electronic controls on these do a GREAT job keeping you on the road and things under control. If a wheel starts to spin or slip, the system recognizes that and attempts to gain control - usually quite successfully.

That's my take..........

 

[Br4hm4]

I can tell you that I used 4H a few times during a few snow storms in the last month or so. Not sure what you are looking for information wise, but I would shift in to 4H at lower speeds then drive it that way up to speeds of 55-60 mph. Would I drive that way all the time? No. But I didn't think running at 55-60mph for a few miles was going to do the Gladiator in. Yes...it still slipped from time to time due to snow on top of ice.

 

[ShadowsPapa]

I can tell you that I used 4H a few times during a few snow storms in the last month or so. Not sure what you are looking for information wise, but I would shift in to 4H at lower speeds then drive it that way up to speeds of 55-60 mph. Would I drive that way all the time? No. But I didn't think running at 55-60mph for a few miles was going to do the Gladiator in. Yes...it still slipped from time to time due to snow on top of ice.

Exactly my experience. Ice is ice and unless you run chains or whatever, you deal with it.
But for snow, icy patches, snow pack, mud, slippery roads - it's great.

 

[uplandgunner]

The nice thing about 4H is you can shift in and out of it on the fly up to about 50mph ( I think the manual says 55). For rain I prolly just stay in 2H and let the TCS do its job. Snowy conditions I shift in and out of 4H as needed if I'm on snow 4H is good, wind drifty snow occasions If I hit some road with more pavement then snow I shift to 2H opposite I go to 4H . Shifting in and out also tends to release any binding and lets you know if you should in 2H more. It sort of teaches you when it's OK.

 

[Red Wagon]

Thanks everyone, this is great information on 4H usage and precautions.

Regarding traction control- My current mid-size truck is a "2WD" Colorado with no limited slip differential. I often end up spinning the right rear wheel mildly when accelerating from a stop, making a right turn on an incline. That's part of my daily commute and parking in a multi level garage. My truck has traction control but I don't get the sense that the left rear is pushing, I think the system is only applying the right rear brake. I have no evidence of this, only a "seat of the pants" analysis.
If this happens in the Gladiator, will the same scenario play out or will power be sent to the left rear wheel? Assume there's no limited slip differential in the rear, in 2H and the model is the Overland.

 

[ShadowsPapa]

Thanks everyone, this is great information on 4H usage and precautions.

Regarding traction control- My current mid-size truck is a "2WD" Colorado with no limited slip differential. I often end up spinning the right rear wheel mildly when accelerating from a stop, making a right turn on an incline. That's part of my daily commute and parking in a multi level garage. My truck has traction control but I don't get the sense that the left rear is pushing, I think the system is only applying the right rear brake. I have no evidence of this, only a "seat of the pants" analysis.
If this happens in the Gladiator, will the same scenario play out or will power be sent to the left rear wheel? Assume there's no limited slip differential in the rear, in 2H and the model is the Overland.

That's how traction control works - it applies mild braking to slow the slipping wheel and that way all torque goes to the wheel with traction.
If the one can't slip, the other gets the power. You won't really feel it "seat of the pants".

If your Overland has the 8.4 radio system, it has off-road pages, I wonder if that shows the traction control in action?
I never tried to look at that on mine.

 

[Red Wagon]

Maybe my Colorado isn't actually a 2WD, dunno...

Thanks Shadows Papa, much appreciated.

 

[canyonrat]

I run 4Hi up to around 50 mph in snow-on-road conditions. Figure if I feel safe driving 55+ then I must not need 4wd.

 

[ShadowsPapa]

I run 4Hi up to around 50 mph in snow-on-road conditions. Figure if I feel safe driving 55+ then I must not need 4wd.

That's about how I decided - need it or not....... if I can go that fast, don't need 4H because that won't help you stop or steer if if things are bad, etc.

 

[jeepguy225]

Quadratec just posted about this.

How and Why to Engage Your Jeep's Four Wheel Drive

https://www.quadratec.com/c/blog/ho...8r7XA314SfkfS8s7oSsOMu5Xu7qUDk5pqAxh8F73IbMgs

 

[WXman]

You need significant "slipperyness" to use 4H, otherwise you could damage the chain inside the t-case, or worse an axle shaft. Rainy roads don't count. I would only suggest using it in snow, mud, sand, gravel, etc.

 

[PyrPatriot]

You need significant "slipperyness" to use 4H, otherwise you could damage the chain inside the t-case, or worse an axle shaft. Rainy roads don't count. I would only suggest using it in snow, mud, sand, gravel, etc.

And even gravel, maybe uphill or if going fast.

I like to think of 4H as more of a tool, whereas AWD is more of a "fun feature" - you don't have to think about it. Kind of like lockers, you have to know when to use them and the consequences of misuse. The difference between a truck and an SUV is that a truck is primarily a tool. Tools misused result in damage, either to the user or the tool itself. An AWD vehicle like a Subaru is more recreational, and was designed so you could have fun with it racing down roads. That's not to say Wrangler's don't have the same restrictions and can't be used for fun. More power, more responsibility. For the greater capability the Jeeps offer, comes more requirement on using them properly

 

[ShadowsPapa]

And even gravel, maybe uphill or if going fast.

I like to think of 4H as more of a tool, whereas AWD is more of a "fun feature" - you don't have to think about it. Kind of like lockers, you have to know when to use them and the consequences of misuse. The difference between a truck and an SUV is that a truck is primarily a tool. Tools misused result in damage, either to the user or the tool itself. An AWD vehicle like a Subaru is more recreational, and was designed so you could have fun with it racing down roads. That's not to say Wrangler's don't have the same restrictions and can't be used for fun. More power, more responsibility. For the greater capability the Jeeps offer, comes more requirement on using them properly

AWD and systems like the cherokee, grand cherokee, Silverado, etc. aren't "fun" - it's security on all roads, wet, dry, sandy, gravel, mud, whatever.. It makes the vehicle more sure-footed.
The system in my Eagle (and other Eagles I've owned) is a blend of the standard t-case with a coupling that allows limited slippage. It's like the JT but can be run all the time. It's a limited slip transfer case. The more the slip, the more the silicone in the coupling acts like a solid - it becomes more viscous with slippage.

Gravel is a great place for 4 wheel drive - it's like any other slick surface in so many ways - I've seen trucks slip and slide on crowned gravel roads, I've seen cars lose control. Maybe Iowa gravel is different due to the glaciers of the ice ages, than what's in other states, but I've run my trucks in 4H on gravel to maintain control when they are badly wash-boarded and rough - because the front wheels PULL the vehicle through instead of trying to push like trying to push a rope or chain.

As far as damage - if you bust an axle you had other issues. That transfer case is the weak link. I have transfer cases on my shelves that demonstrate that. I replaced the t-case in my car because the coupling blew from abuse by the PO. (prior owner)

The best part about the Jeep system is that it LOCKS the front and rear axles together. It's strong, it's reliable, unless abused on dry surfaces. That chain is tough, but it's held together by links and pins - it will wear and can break.

If you see a Prius whiz past you at 85 mph, you do not need 4H.
If the roads are only wet and you have traction issues - look to your tires or driving habits.
I've used 4H in cases of roads well worn where water sits in the tracks made by heavy trucks and you hydroplane. But just wet- put sand bags in the back and call it good.
Transfer cases are not cheap to fix.

The right tires, rated for the roads you see most, a bit of weight in the back, 200-300 pounds of sand bags if it's winter,, snowy, whatever, (like TODAY here- winter storm, AGAIN, ice and snow mix,) and reasonable driving by the driver............

 

[MarineHawk]

As a side note, get great tires, and you won't need 4H as much. We got about 2" of snow/sleet a couple of weeks ago. It was pretty slippery. When in 4H, I could not get my Cooper STT tires to break loose when hitting the gas hard at 20 mph. I could get the tires to break loose under the same conditions in 2H. But I never lost traction when driving normally in 2H.

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