I just read on another thread about this. When driving in 4wd the drivetrain binds up. I am not sure what they mean by this. Also they say driving 4wd in normal conditions is bad for the car? I never heard that? I tow and pull alot with my blazer and with a heavy load I will put into 4wd for power . I do not think I was harming the truck but if someone knows something please reply.

 

4hi will never give you more power. If you are dropping it down into 4lo, then you will have more torque multiplication (more power), but the extent of that is limited to traction. 4lo is typically for getting stuff pulled out where you need the torque multiplication and have enough traction to use it. Spinning in 4lo is not a good thing as it is MUCH easier to over rev in 4lo because the engine doesn't have to work as hard.

You will actually get a little less power in 4hi vs 2hi due to higher drivetrain losses (the reason why you get lower fuel mileage in 4hi vs 2hi). The only time you should need it in 4hi is when you are loosing traction in 2hi. What I always used to do, when pulling a load, was to use 4hi to get everything moving (low speed), then switch out to 2hi. In my old '97 Ram 4x4, you knew when you were in 4hi driving fast. The slightest turn would remind you with a weird howl from the tires when traction was good.

In lower traction situations, the binding will be aleviated by the tires (by way of increased wear). With higher traction however, the tires are sticking much better to the road and can not slip to 'unbind'. This is where drivetrain damage can occur. Things like accelerated U-joint & CV joint wear to premature front and transfer-case diff failures can occur.

If you have a vehicle with 'Auto 4wd', use that instead of manually putting it in 4hi. If not, then only use 4hi in low traction conditions and switch back to 2hi once underway. Also, if you are using 4hi so you can get up to speed faster when towing, you probably should be in 2hi and accelerating slower due to the weight. You shouldn't need 4hi to get a load moving on dry pavement, just a little throttle control to keep from spinning.

 

Read your owner's manual. Do not use 4WD in normal driving conditions. This also does nothing to save your transimission when towing. 4WD is for added traction capability. When traction is good, you are putting premature wear on your 4WD components when in 4WD.

 

Think of it this way, when going in a straight line, there will be no added wear as all wheels are turning at the same speed.

Now when you turn, the outside wheels are turning faster than the inside wheels. When in 4wd, the transfer case locks the front and rear axles together, forcing one tire on each to spin at the same rate. Even the slightest turn will cause the drivetrain to bind, but obviously the degree of bind directly relates to the amount of a curve. And this only applies in high traction situations where the wheels are not allowed to slip.

**EDIT - Corrected per Hanr3's post below

 

Not entirely true. The front axle does not lock in the sense you are referring to, it doesn't have a factory locker and it won't bind. Our trucks have a open differential, and the tire with the least amount of traction will spin the most. While the other tire will do nothing. If there was a locker, both tires would spin at the same speed, except in turns.

Binding- Hmmmm. Lets see IF I can explain this without writing a novel.
The transfer case has a chain in it. When you shift into 4hi or 4lo you shift so the chain locks the front and rear axle together. The front and rear axles spin at the same speed. The only exception to this is on AWD vehicles that have a limited slip type of transfer case. Slip being the key word. With a chain, there is no slip. The only difference between 4hi and 4lo is the gear used in the transfer case. While in 4hi the gear ratio is 1:1, while in 4lo the gear ratio is 2.62:1. In other words, while in 4hi, every revolution of the input shaft on the t-case results in one revolution on the front and rear axles. While in 4lo, every rotation of the front and rear axle the input shaft turned 2.62 times.

Now when you turn the truck (like around a corner), every tire follows a different path. Drive in a semi-circle on wet grass, snow, or a wet road. Stop before you complete the circle. Notice the path of each tire. The outside tires traveled further, even the front and back tires followed a different path. Even while driving on the interstate you make turns. Gradual as they may be, they are still causeing each tire to follow a different path. It takes about 45 miles for my wife to notice the hollowing. The binding is the result of the different path each tire takes, plus the front and rear axle are locked together cuases the drivetrain to bind up.

Lockers are something different and can add to the problem, however they also greatly improve the trucks capability in low traction situations. Lockers are another subject. I think the best place to understand this is on a site called "Howstuffworks.com" They have a great pictoral demonstration along with text to explain what your looking at. Please ask if you still don't understand.

http://auto.howstuffworks.com/four-wheel-drive.htm

 

Ah ok. I always thought that the front axle on my old Ram had a limited slip in it and that was why it would hop all around when tight turning in 4wd. Thanks for the clarification. It makes sense. 2 Wheels (one front, one rear) will have to always travel at the same speed when in 4wd and there isn't a turn in the world that would satisfy that situation. Cool! Learn something new everyday.