4wd & dry pavement "No"

[mschuyler]

I've read a couple of places that one should not engage 4wd on dry pavement. Well, why would you want to? But still, what is the reason one shouldn't? How about other conditions? Off road--of course, but what are the "rules" of using 4wd given certain weather conditions: Snow? Wet? Could someone do the basics here or even point to a tutorial? I looked half a dozen pages into the forum and didn't find it. TX

[Trouttrooper]

Probably the most common reason would be the need for the extreme low gearing from 4lo to go up a steep incline with a heavy load.

 

You need to understand how 4 wheel drive works to know why you shouldn't use it on pavement. In 2 wheel drive the front tires aren't connected to anything so they can rotate at any speed they want. With 4 wheel drive engaged you are making a direct connection between the front and rear axle's. This means that one of the front tires and one of the rear tires MUST turn at the same rate (remember standard differentials will allow different rotation speeds between left and right tires on an axle). This is fine in a straight line BUT when you turn you are now making each tire rotate at a different speed. There is now a conflict between the front and rear axle because they physically can't do this when in 4 wheel drive (unless you had a differential between front and rear axle like all wheel drive minivans etc.) The solution that happens is one of the tires will spin or slip to make up for the different turning radius. When you are on dry pavement there is so much traction available that none of the tires are willing to slip. This causes the drivetrain to bind up and possibly break a u-joint or worse. In snow, mud, or ice there's not as much traction so it is easy for a tire to slip to compensate for different turning radius.

[Buggle_96]

Probably the most common reason would be the need for the extreme low gearing from 4lo to go up a steep incline with a heavy load.

 

You need to understand how 4 wheel drive works to know why you shouldn't use it on pavement. In 2 wheel drive the front tires aren't connected to anything so they can rotate at any speed they want. With 4 wheel drive engaged you are making a direct connection between the front and rear axle's. This means that one of the front tires and one of the rear tires MUST turn at the same rate (remember standard differentials will allow different rotation speeds between left and right tires on an axle). This is fine in a straight line BUT when you turn you are now making each tire rotate at a different speed. There is now a conflict between the front and rear axle because they physically can't do this when in 4 wheel drive (unless you had a differential between front and rear axle like all wheel drive minivans etc.) The solution that happens is one of the tires will spin or slip to make up for the different turning radius. When you are on dry pavement there is so much traction available that none of the tires are willing to slip. This causes the drivetrain to bind up and possibly break a u-joint or worse. In snow, mud, or ice there's not as much traction so it is easy for a tire to slip to compensate for different turning radius.

 

This is also why there is a difference in the front a rear ratio, like the front will be 4.10 and the rear is 4.11.

[StoneyPgh]

This is also why there is a difference in the front a rear ratio, like the front will be 4.10 and the rear is 4.11.

Haven't ever heard there was a difference between front and rear 4X4 axles.

Could you reference some info on this statement?

[lsufan]

I have never engaged 4x4 on dry pavement, but I have run 65 in 4x4 on dry pavement with no problems on my 98 z71. On my 2500hd I drive in 4x4 a good bit on the icey/snowey roads on my 24 mile drive to work. It was always in high range, I never use low range when speeds are going to exceed 10-15 mph.

[bigred91]

i have a 91 k1500 4x4 and I have replaced both front and rear differentials. They are exactly the same ratio. 3.73. the only trucks that have different ratios are the old dodge rams with dana axles

[ZZ327]

you should never run 4wd on dry pavement because you bind up the transfer case. You can feel it when you try to turn at lower speeds.

 

if youre running on dry roads in 4x4 with all wheels spinning similar speeds its fine.

I only have ever used 4 low when Im really stuck!!

[xsports33]

I have a question along the same lines, i don't mean to hi-jack.

 

Is there a top speed that 4x4 should not be run over? even in straight line?

[Trouttrooper]

I have a question along the same lines, i don't mean to hi-jack.

 

Is there a top speed that 4x4 should not be run over? even in straight line?

 

in 4hi not really. Just figure if you're in 4x4 that means road conditions are bad enough to not be going 80+ mph. 4Lo I think it says 45 mph but you're engine would be screaming at that speed. I've never gone faster than 25 mph in 4Lo