I've never owned a 4WD vehicle before, so I'm still wondering, why does my owner's manual say not to drive in 4Hi on dry surfaces? My truck is a 2005, and a coworker that I trust (a lot) on automobile matters tells me that it's more relevant for older vehicles and that it'd be fine if I wanted to drive in 4Hi anytime I wanted. I know it'll hog loads of fuel, and I don't plan on doing it, but I was wondering if someone could explain the mechanics of it (in more or les layman's terms) and what would actually be safe.

 

When the truck is locked into 4 wheel the tires rotate at the same speed. This isnt a problem if you're just driving in a straight line.

However if you try to turn the inside wheels (left turn, left side wheels. right turn, right side wheels) will try to turn faster than the outside wheels due to the smaller radii. The differentials wont allow it since theyre locked into 4 wheel creating wheel hop on really tight turns as the tires are twisted until they lose grip and jump forward to meet back up with the same position as the outside tire.

When in 2 wheel, the wheels arent locked and the inside and outside can spin freely independent of each other at different speeds.

hope this helps

 

Your buddy is very wrong, do what your owners manual says. 4HI and 4LO are meant for low traction surfaces only, you can cause some serious drive train damage if you use either on dry pavement or any other high traction surface.

Here, click this link, it covers in depth how 4x4 and all wheel drive systems work and what the differences are. http://www.google.com/url?sa=t&rct=j...HbhGA1afWfTlfA

 

I wouldn't trust your coworker with any more automotive advice...He couldn't be more wrong!!!

 

Then why don't AWD vehicles have this
problem? I don't have lockers, otherwise, this would be an issue for the back wheels as well when just in two wheel drive (it's the outside tires that move faster btw, that I do know).

 

Because it only goes to AWD when the computer or module senses slippage. On normal dry roads it operates in front wheel or rear wheel drive only.

 

My wife has a AWD Explorer. The front diff is not the same as a 4WD. The diff is an open style and allows the wheels to turn at a different rate. Most AWDs are 1/3 front, 2/3 rear drive. The computer or clutch senses slippage and transfers power to that side.

 

Listen to what everyone just said as they are correct. But, should you choose to challenge the advice they gave you, just throw her in 4HI and give her hell on dry pavement. Just don't ask any of them for $$$ to replace your tranny or whatever else you ended up destroying afterwards. Don't feel bad. I recently found out the "reason" why 4WD doesn't work on dry pavement, but I've known for 20+ years NOT to do it. 4WD and AWD are two different animals.

 

AWD systems are much more complex than 4WD systems and a completely different setup.

when in 2wd the diff is open and allows for the tires to rotate freely of each other. turn the traction control off and stomp on the gas, the 1 wheel peel is proof of that.

FYI I wouldnt drive around in 2wd either with the diff locked on dry pavement

 

I believe this quote from Wikipedia does a good job of summing it up (and if you check the link it explains other types of 4WD/AWD systems)


http://en.wikipedia.org/wiki/Four-wheel_drive


So, no, driving on dry pavement in 4Hi is not good. Your truck isn't going to instantly explode if you do, but you are placing unnecessary stress on driveline components. I don't believe you can damage the engine or transmission doing that, but you could certainly damage the transfer case, front/rear diffs, axles, hubs, etc.