I was messing around with the 4-wheel drive in my '07 Jeep Liberty, and I was telling my friend about how it performs better with it engaged. My friend told me that you shouldn't use 4-wheel drive when you don't need it because it will burn up the differentials. I'm no mechanic, but I have a basic understanding of how cars work and I have no idea why using your 4-wheel drive on the road would be harmful to the system. Could you explain why this is or is not true?
Your friends are right. Your owner's manual probably says the same thing.
The basic principle is this: when you going around a turn in your jeep, each of the four wheels is turning at a different speed. (different radii)
But differential locks and some transfer cases prevent wheels from turning at different speeds, so taking that turn makes your jeep fights against your driveline. On dirt, mud, snow, sand etc. this isnt a problem because the wheels can slip a bit to relieve pressure on the driveline. But pavement grips really well, so it puts tremendous pressure on your driveline. The wheels will occasionally break free of the pavement from the build up pressure (like a wound up clock springs), and that's why you get "crow hop" and tire chirp. This is also why part time 4WD systems have poor handling and feel "squirrely" when turned on.
AWD systems are different .They're designed for use on pavement. They prevent some wheel spin, while at the same time allowing speed differentiation at each wheel so that vehicle can navigate turns without losing grip.
http://www.4x4abc.com/4WD101/def_turnpart.html
You will just use extra fuel and wear out the components.
My general rule of thumb when it comes to using 4 wheels to drive the vehicle. AWD vs 4WD.
If the car automatically uses all 4 wheels as part of its normal drive, then using all 4 wheels is fine. This is usually referred to as AWD, or All Wheel Drive.
However, if you have to engage 4 wheel drive yourself, for special circumstances, then it is probably smarter to use it when you need it. And disengage it when you don't need it. This is usually referred to as 4WD, or Four Wheel Drive.
Anyhow, like folks said above, look to your owner manual. Some systems can handle it 24/7, some systems can't.
Don’t do it! I would engage my 4WD on dry pavement sometimes. Doing that burned up my front axle and transfer case.
If you have a center differential you can drive on the road in 4WD. I'm not very familiar with the Liberty, but the old Jeep Cherokees that preceeded it came standard with a part-time NP231 transfer case. With those you could only use the 4WD under slippery conditions or risk damaging the drivetrain. An optional NP242 transfer case was available that added a full-time 4WD position. With that option the Jeep could be left in 4WD all the time if desired.
As others have said check your owners manual, but I'd say that if your transfer case only has something like 2H-4H-N-4L positions it is part-time only and the 4WD should not be used on dry roads. If you have full-time capability there would be a position for it on the transfer-case lever.
