Being new to 4x4 ownership, I had no idea when it was OK to use 4WD and when it wasn't. I had no idea that if you ran four wheel drive on dry pavement that you could break something. This is important reading for people curious about when to use it. In short, there are two views: on-dirt-only purists, and as-appropriate-on-and-off liberals. I write from the liberal perspective, as I value my safety and confidence higher than my vehicle parts.

Jeep Wrangler TJ 4WD

I believe that the stock Jeep Wrangler is one of the highest performing off-road vehicles you can buy on a showroom floor and drive directly to a trail. On top of being a great stock vehicle, it is highly configurable and maintainable by any hobbyist mechanic. What a fantastic 4x4 this little square box is!

You would think that Jeep, or the parent company Daimler Chrysler, in building the absolute pinnacle of off-road vehicles ever made, would have decent instructions in their owner's manual for when it is safe to use four wheel drive (4WD). But they don't, and most owners end up using their 4WD at inappropriate times as a result, or coming on the Internet and asking about in confusion as to when it is OK to use.

I figured I would help put an end to this recurring crisis by writing an article that reviews what I know about the 4WD, which isn't necessarily very much, and when it is appropriate to use it. Hopefully, those of us tired of repeatedly answering this question can point people to this article and put the issue to rest for the most part.

WARNING: Rather than using this as a reference you should always read your owner's manual, and if you don't have one, you should definitely get one from Jeep and read it thoroughly. Advice on when and how to use the 4WD in your Jeep, as well as how to maintain it, is scattered all about the owner's manual. Without reading it thoroughly and repeatedly, you will probably damage your vehicle and make costly mistakes.

THIS ARTICLE IS ONLY HELPFUL TO PEOPLE WHO HAVE ALREADY READ THE OWNER'S MANUAL COMPLETELY. READ YOURS BEFORE CONTINUING.

What Does 4WD Do?

Normally, when you are cruising down the road in 2WD in your Jeep, the rear wheels do the pushing, and the front wheels do nothing but help you steer. The Jeep's engine burns fuel and air using electrical spark to turn a crank shaft, and that crankshaft turns gears inside the transmission. The output of the transmission goes into the transfer case, the the transfer case output goes to the rear drive shaft. The rear drive shaft in has a pinion on it which turns inside a ring gear in the rear differential. This ring turns the axles in back, and as a result, the rear wheels have power.

If you pull the lever on your center console that engages 4 HI, you are turning on 4WD. That lever controls the transfer case, and it makes the front drive shaft receive power from the transmission the same way the rear drive shaft does. The transfer case transfers power from the transmission to both drive shafts.

Doing this forces both axles to have driving power to them. It is very effective because the front wheels are also receiving power, and whichever of the four wheels has the vehicles weight over it is able to provide thrust. Also, the front wheels are under the weight of the engine, so they often have better traction. With 4WD engaged, your Jeep may feel like it is on railroad tracks by comparison to 2WD.

The first time you take your Jeep somewhere slippery and pull up that lever and go into 4 HI, you will be surprised how your Jeep goes from being out of control to behaving as though it is on pavement. I certainly was.

Jeep Wrangler 4WD Settings

Normally, you should leave your Jeep in 2H almost all the time. If you go off-road, and you need more traction, you can put the Jeep into 4H and have four wheel drive. These two gears are called "high" because they retain the standard gear ratio in the transfer case for normal operation at normal speeds. If you switch into Neutral, this is not the same as neutral in your transmission. It disengages the gears in the transfer case. Usually this is used when you want to tow the Jeep with some wheels touching the ground. It frees up the wheels completely from the engine output. Lastly is the mysterious 4L.

4L is very low gearing. Depending on your transfer case model, you get low or really low gears. The Jeep will not go very fast in this setting, but incredible amounts of power are delivered to the wheels for use in extreme conditions.

I can report to you from my experience that putting the Jeep in 4 LO means it will crawl slowly and deliberately over most terrain and many different obstacles - as long as your tires and clearance hold up under the strain. Your Jeep is very unlikely to ever have a problem because of its inability to grip terrain due to the drive train. More likely is that you will have poor tires for off-road and they will either fail to grip or be damaged. It is also more likely that you will grip just fine but have insufficient clearance or armored protection and therefore damage the body or underside of your Jeep while off-road. The engine, transmission, and transfer case will almost never let you down. It's an amazing vehicle!

Jeep's Part Time 4WD

The owner's manual for my 2004 Jeep TJ says, "Driving on dray hard surfaced roads may cause increased tire wear and damage to the driveline components." That warning is very important and probably ought to be on a bright yellow sticker on the transfer case shifter handle for all folks new to 4x4 vehicles.

Jeep's 4WD system is a part time system. That means that you should only engage it when there is a necessity for using 4WD or when the owner's manual recommends it. The reason for this is that 4WD forces both axles to turn at the same speed as each other. Because both of them are locked into the transfer case, they must both turn at the same rate of turn from the transmission. However, the front gears that connect the front drive shaft to the front axles are slightly different ratio than the gears in the rear of the vehicle. For example, if your Jeep has 3.73 gearing in the rear differential, the front is 3.74.

In 2WD, this doesn't matter, because the axles in the front and the rear are not locked together to turn with the same power, so the front is turning freely in synch with the rear wheels instead of being slightly slowed by the differing gear ratio. Also, the wheels in front and the back will turn at slightly different speeds when cornering. This means that you need a slippery surface to use 4 HI or 4 LO in a Jeep Wrangler. If you use 4WD on a surface that is slippery, the tires can slip a little in case the axles are a little out of synch with one another. The part time 4x4 without any ability to slip goes from being a fantastic off-road machine to being a self-destructive device that grips the road too much for its own good on pavement.

If you use 4WD on dry pavement, you may experience your tires jumping occassionally in order to relieve tension that builds up in the transfer case from the axles turning at a slightly different speed. This puts a lot of strain on all components from the differentials to the drive shafts, and most especially on the transfer case. You may, in fact, total your transfer case by causing it to bind up. One axle is trying to to make 1/2 rotation while the other wants to make a full rotation after a turn in which the front wheels travel farther than the rear wheels. Pop! You've broken an expensive element in your drive train, and now you need a tow, because the transmission can no longer output to the rest of the car.

The repair cost? It costs $3000 or more including labor to replace your transfer case. Good luck getting this done under warranty!

Therefore, YOU MUST NEVER USE 4 HI or 4 LO ON DRY PAVEMENT.

Engaging 4H or 2H

Before you try to engage 4H in your Jeep, makes sure you have the minimum requirements:

Same Tires on All Four Corners. To activate four wheel drive, you don't need much. Make sure that all four tires are the same size. If you have an off-size spare that is currently mounted, then you cannot engage four wheel drive. You also cannot engage it if you have different size tires front and back. All four donuts must be the same size.

Drive under 55 MPH. You can pull up the lever into 4H as long as you are going under 55 mph. That being said, anyone who engages 4WD when he is going that fast is a moron, because if you can go that fast, you do not need 4WD. 4WD is specifically for when you cannot go fast at all. This just means you will not break anything if you engage it at this speed.

Dirt. You should be on a the preferred loose, slippery surface, but not yet in a situation where you could get stuck.

Same gears front and back. If you recently regeared only one differential, no 4WD for you. The gears in the front and back must be almost identical for 4WD to not result in catastrophe for your vehicle.

Some tidbits about 4WD that novices sometimes ask come to mind.

Reversing. 4WD works in reverse and various gears on an automatic transmission. Don't be afraid to reverse if you are new to 4x4 vehicles.

Disengaging is the same. To disengage, just push the lever down. You should feel and maybe hear a "thunk" noise as the transfer case is shifted back to 2WD. Just to make sure, once you are clear of slippery surfaces, try reversing for about 50 feet, and then drive in a figure eight a few times, and you can ensure 4WD is disengaged and the transfer case is back to normal. This maneuver is not necessary, though.

Engaging 4L

To go into 4L is real off-roading. You should already be in 4H, which is really easy to get into. Put your clutch in or put your auto tranny into N, and then pull the transfer case lever up to N and on through without stopping to 4L. It might engage, it might not. It can be stubborn as heck and require some repeated tries to get it to work. Try rolling no faster than 2 mph and repeating the attempt to get it into 4L if it won't take. You will know when it takes.

Getting it out of 4L can be as tricky. If it gets stuck and will not cooperate, try rolling a little, driving a bit before you try again, or if all else fails, shut off the engine and restart it and try again.

How Fast Can I Go in 4WD?

Read the owner's manual to find the correct speeds you should be going when you engage and disengage 4WD. But that's not really what you meant, is it? You want to know how fast you can go with 4WD already engaged? The best answer I have ever read to this question is that if you have to ask, turn off your 4WD. It should not be turned on if you are not scared to go faster than 40-45mph. If you think you can do 70 mph down the expressway, turning on 4WD and trying to go this fast seems to me to be a recipe for catastrophe. It would combine the worst of everything: inappropriate conditions, high speed, and the transfer case binding. The dark part of my mind gets a delicious rush of glee imagining some idiot's transfer case melting and seizing up, causing his Jeep to pop off the road and fly through the air.

Road Conditions and 4WD

Opinions on when it is appropriate to use 4WD in a Jeep Wrangler TJ vary from person to person. The owner's manual for my 2004 Jeep Wrangler TJ (yours may vary) says:

Be especially careful while driving on slippery roads, in close-quarter maneuvering, parking, or stopping. Remember, always engage 4-wheel drive when driving on slippery roads. (page 174, left column, 4th bullet point)

Do not drive too fast for road conditions, especially when roads are wet or slushy. A wedge of water can build up between the tire tread and the road. This hydroplaning action can cause loss of traction, braking ability, and control. Under such conditions, engage 4-wheel drive. (page 174, left column, 5th bullet point)

That doesn't really tell me a whole lot about when I can use my 4WD in my Jeep, and I am itching to pull up on that lever. In fact, if I read that advice, it makes it sounds like the minute it starts raining, I should engage 4WD and run around town with a big fat smile on my face. It makes it sound like 4H will solve problems with hydroplaning and slipping on the road that can happen when streets are wet. It makes it sound that way, but the owner's manual never really comes out and says anything as bluntly as it should.

Jeep lawyers must have carefully crafted the language in the owner's manual to ensure that no one would be able to blame them for failing to recommend 4WD under slippery conditions and yet be protected from accusations that the manual recommended that you harm your Jeep components. The owner's manual is written in a vague fashion to allow Jeep to give appropriate advice without causing them legal exposure. Also, the different scenarios under which you might use 4WD or not are controversial. Being weasels, the guys who wrote the owner's manual ducked the controversy by not talking about wet pavement or pavement with large, intermittent icy patches. They say definitely use 4WD off road, and definitely don't use it on dry pavement. That is not helpful. The owner's manual is a big, fat dodge out of the whole issue whether or not you can use your 4WD on wet pavement.

So, when can I use my 4WD? One Jeep enthusiast who is fairly expert on most things Jeeps, Jerry Bransford, says, "... a part-time 4wd should never be used on a paved street unless it is covered in snow or ice. Not even when it's raining." That's pretty standard as far as the advice off-road enthusiasts give.

Under what conditions can I pull up the lever?

A dirt or gravel road - You are probably safe to engage 4H on a dirt road. Just remember to turn it off before you hit the pavement. A lot of people forget to disengage 4WD when they reach pavement.

A beach - You are probably safe to engage 4H on a beach, because sand is slippery. Just remember to disengage it when you hit pavement. There is no warning light or buzzer that sounds when you hit pavement.

Snow - If it snows, and there is snow standing on the street, and you cannot see the asphalt underneath it, and if you rev up the engine and the back wheels slip, then you are probably safe to engage 4WD even on a paved street. Be careful, because if you driving through snowy patches and then hit dry pavement, you need to remember to turn off 4WD.

Ice - 4WD is great for ice, except that ice tends to come and go on streets, and you will hit dry pavement, and your 4WD will be engaged. I guess it depends on how much dry pavement you might go over. Occasional dry pavement patches will probably not hurt anything, but if you leave the ice, and you forget your 4WD is engaged, then you are in trouble.

Mud - Deep mud might be best handled in 4L, going really slow, with appropriate mud terrain tires, since all terrain tires don't grip in mud very well. You are definitely safe using 4WD in mud.

Dry, Paved Streets - NEVER USE 4WD ON DRY ASPHALT.

Wet streets - the owner's manual says "yes", but the off-road enthusiasts say "no." The jury is still out on that one, however.

Can you use 4WD in the rain?

What about rainy streets? If it is raining heavily and water is standing on the streets such that you are afraid to go faster than 40 mph, then you might be able to get away with engaging 4H without breaking something, but Jeep experts don't think so, as one wrote me,

Being in 4wd does NOT have the slightest effect on hydroplaning. If you are hydroplaning in 2wd, you will STILL be hydroplaning once you shift into 4wd if you do not also slow down.

But the owner's manual seems pretty clear in that it specifically recommends that you engage 4WD on slippery streets. I guess the question is how hard does it have to be raining before a street is slippery, and does 4WD actually help? I wasn't too sure, not being an off-roading expert nor a mechanical engineer, so I experimented to figure it out for myself. I drove home from work during a horrible rain storm, and I threw caution and my drive train components to the wind.

I engaged 4WD to see what would happen.

A small *clunk* and suddenly the Jeep felt like it was glued to the road. I see why the owner's manual warns against over-confidence on corners under bad conditions. I mean it stuck and didn't move when going through huge puddles and conditions where normally it has given me some trouble with sliding, slipping, or starting to fishtail, etc.

When the rain died down to a drizzle and the streets were no longer filled with standing water, I disengaged it, and there I was back in the dangerous-to-drive Jeep that I am familiar with. So I put it back on. Again, total control and very tightly gripping the road.

When I got home, I disengaged 4WD, drove in reverse for about 50 feet, and then pulled it into the garage.

All in all, I did 20 miles in 4wd at 35-45 mph on pavement in the rain.

No negative effects at all. Everything's fine. No increase in engine temp, no weird bumping, grinding, or vibrations. No more (or less darn it) noisy than before. Everything looks good, and I was a lot safer on all that water through Georgia's back roads.

I wish I had read the owner's manual more carefully when I bought my Jeep, and that I had been doing this all along. I let people scare me away from every touching the transfer case shifter and so never used 4WD unless off road. And all this time I have been missing out on what a fantastic vehicle this is to drive in the rain. Holy cow!

In a heavy rain, 4WD should be safe to use. This is my idea of the least amount of rain that would qualify for use - at least 1 inch deep water on the streets, and traffic pushing for you to go at least 35 mph. The cars leave a wake and make rooster tails spout behind them all the way down the road. Puddles are deep. Even then, disengage 4WD if the road clears up a little.

I repeated this experiment a few times - I drove during heavy rain storms when there were large puddles of standing water, much water flowing down the road into gutters, and streams coming out of their banks on paved streets with 4WD engaged. So far, I have ten hours and 150 miles driving like this without any of the tell-tale signs of 4WD on dry pavement type troubles. The Jeep doesn't hop, the handling is not odd, and my transfer case is in fine condition, so far, and it has almost 40,000 miles on it.

After having this experience, however, I can understand the warnings from people about using 4WD under the wrong conditions. From what I felt driving it last night, if the pavement had been dry, that gripping it was doing would have not been able to slip around and I can see why the drivetrain would turn into a molten pile of steaming, glowing, goo.

I can also understand how tire wear would increase, given the increase in the friction coefficient from the 4WD being engaged.

So, I would never use it on dry pavement having had this experience. I'd expect a thunk and then the sound of grinding spinning broken chains and gears doing that.

My experience was that I was able to use 4WD to get better performance in horrible conditions. Of course, I also did other common sense things like slow down, turn on my lights, and pay close attention to road conditions, remembering that 4WD was engaged.

In fact, I have to say that my experience is that the biggest risk of driving 4WD on pavement is forgetting to turn it off when road conditions improve and you find yourself on dry pavement, which is always a bad thing for 4WD.

But in the rain on solidly wet streets - my goodness - what a machine!

Dumb Uses of 4WD

Some people are determined to be in 4WD because they think it is manly to use it, and it makes them feel special to be driving a vehicle that can do things other vehicles cannot. Sometimes, these people engage 4WD in conditions where it is obviously not appropriate. I think some of these fall under the heading "Hey y'all! Watch this!"

Not Much Snow - A few flurries with no accumulation on the streets still counts as dry pavement. Do not engage 4WD.

Wet Streets - Streets wet from a previous rain are nowhere near as wet as the streets I performed my experiment on. I drove through 1 inch deep water all the way home. Streets wet from a light misting are probably still not slippery enough to engage 4WD.

Your Yard - Don't off-road in your yard, especially if you have a little yard 50 feet wide and about 20 feet deep. Your neighbors will think you are an idiot, and your wife will kill you when she gets home. Don't off-road in your neighbor's yard either, for that matter, nor on any private property that is posted No Trespassing. Buckshot in your spare tire does not make off-roading more adventurous.

Dry Asphalt - NEVER USE 4WD ON DRY PAVEMENT! I can't say this enough. Just don't do it. There are no benefits, and you might damage your vehicle.

The Greatest Danger of All

It is important that you remember the biggest danger in using 4WD under any conditions: forgetting to disengage it when you hit dry pavement.

I hope this article has helped sort out some questions about 4WD usage with the Jeep Wrangler TJ. It certainly seems to pop up often enough, and I certainly wondered for a long time when it was appropriate to use it. After reading the owner's manual several times all the way through, highlighting all references to 4WD, and reading tons of explanations about it on the Internet, I feel more comfortable using mine.

Enjoy your Jeep!

Feedback

Bob writes:

About the article on when to use 4WD. I have a 96 Cherokee YJ 4L 4WD. I put it in 4WD when it rains all the time. For 10 years now and over 300,000 miles on it. No repairs to the drivetrain at all.

Other Sources about Jeep 4WD Use

Cars.com Article on 4WD. Jeeps use part time 4WD. This is a great article with moving flash images showing you how it works. They say "Do not use part-time 4WD on pavement.

Jeep Forum 4WD - When to Use - Lots of great advice from those who know better than anyone - the guys that live and love Jeeps.

Another Jeep Forum Discussion of 4WD - Members of Jeep Forum chime in about 4WD and when it is OK to use it.

About.com 4WD Use - Short and to-the-point for those of you who hate my overly verbose and flowery turn of phrase.

Order an Owner's Manual Online - Did you lose your owner's manual, or did you buy used and not receive one? Definitely get one and read it cover to cover twice before you assume you know what you are doing. The easiest way to remove the soft top, the best gasoline to use, the amounts of fluids, and a schedule of maintenance are just some of the benefits of the owner's manual. Get one!