Never Use Part Time 4WD on Pavement – and Why!


Today, lots of trucks come with part-time 4WD which is great if you’re a weekend off-road warrior with a truck modded with bigger tires, steel bumpers, and an open fender system.

Then you can hit the trails and mudholes or have some fun in the snow with the 4WD as long as you use it safely.

It’s important that you remember to turn off the 4WD once you hit the streets again; the last thing you want to do is use it on dry pavement.

If you do, you could end up seriously damaging your transmission due to a condition called driveline bind or axle bind.

What Is Part-Time 4WD?

Vehicles that have part-time 4WD are those that offer drivers the best of both worlds, at least to a point.

You can drive on regular pavement in the best of conditions, then push a button and have the benefit of 4WD when you need it.

Part-time 4WD is designed only to be used part of the time when conditions warrant it.

If you continually use your part-time 4WD on the pavement when there isn’t a need, you are predisposing yourself to a very expensive breakdown.

Driveline or axle bind will eventually wear down your differential and simply stop the front axles from moving, usually to the point of breaking something very expensive within the transfer case.

What Is Driveline Bind?

Driveline bind, also called axle bind or driveline wind up, is what happens when one or more components within the driveshaft on a part-time 4WD truck bind up so there is reduced or restricted movement - or it actually break.

This happens because in a part-time 4WD vehicle, the front wheels rotate faster than the rear simply as a matter of design.

On lower traction surfaces that are safe for using 4WD like sand, snow, mud, and ice, that difference in speed is reduced by a bit of natural tire slide.

It levels the RPMs between the front and rear driveshaft and lets the 4WD work without any damage happening to the drivetrain.

When used on high traction surfaces like pavement, the faster turning front driveshaft ends up forcibly slowed down due to the amount of traction the front tires have on the pavement, preventing them from spinning or sliding.

This binding breaks down the lubricant in the differential faster and wears the driveshaft parts more, usually resulting in something binding or breaking after some time.

Why Does Driveline Bind Happen Only to Part-Time 4WD?

Driveline bind typically only happens in trucks with part-time 4WD due to a difference in the differential in comparison to the differential in full-time 4WD and AWD vehicles.

The part-time 4WD differential is designed with driving on the pavement the priority, although it can be safely driven in 4WD under the right conditions as the differential does not level the speed between the front and rear driveshaft.

Part-time 4WD relies on tire slide to correct the vehicle, which is why part-time vehicles may not have the best ride when in 4WD; they usually oversteer.

The differential in full-time 4WD and AWD vehicles are designed to accommodate the difference in RPMs between the front and rear driveshaft.

In doing so, all drivetrain parts continue to work smoothly without unnecessary additional strain or heating up the lubricant that could cause it to break down prematurely.

Although it’s still not recommended as it can affect driving safety, these vehicles can be driven in 4WD on high traction surfaces like pavement without the risk of damaging the drivetrain.

Avoid Driveline Bind with Your Part-Time 4WD

As convenient and fun as it may be, a truck with part-time 4WD is not the same as one with full-time 4WD or AWD.

Avoid the costly damage you could inadvertently cause by always taking it out of 4WD when driving on high traction surfaces - save your money for heavy-duty steel bumpers and open fenders.

Enjoy it elsewhere, but be careful on the pavement!

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