4WD Glossary
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© 1996-2006 Harald Pietschmann


Four wheel drive systems
"Part Time 4WD" 


Main mode is 2 wheel drive for everyday pavement use. Usually only rear wheels * are powered.

When needed (usually beyond pavement) 4WD can be engaged.

4WD is used part of the time.

When 4WD is engaged front wheels are powered as well - if the vehicle has manual hubs on the front wheels, they need to be locked first.

There are two different settings for 4WD - "high" and "low" 

4WD "high", sometimes called high range, cannot be used on dry pavement with a "part time " system.

For extreme situations 4WD "low"is available, it cannot be used on dry pavement either.

4WD "low", also called low range, does not provide more traction,
however, it provides two to three times more torque at about half or a third of the speeds in high range.

 * In some cases front wheels are powered instead

Part Time 4WD requires:

a transfer case

two drive shafts

two axle differentials

two powered axles

Part time 4WD has no center differential !

how to properly use part time 4WD 

how to shift into 4WD

when to engage the hubs

Useless on pavement or high traction surfaces

full time 4WD - all wheel drive - automatic 4WD - combination systems

| 2WD use of traction | 4WD layouts | crawl ratio | 4WD components | do you need 4WD? |

Learn from professionals to get the most out of your 4WD:

2005 hands-on 4WD seminars