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All-Wheel Drive

Billions of dollars worth of marketing has firmly lodged into the brain of many a vehicle buyer that they need All-Wheel-Drive or else they will instantly pirouette off the road to their death at the slightest hint of snow, or that they'll be relegated to pavement at all times and get stuck the instant they even look at a gravel road.

Reality is somewhat different. While AWD has it's uses, the usefulness is vastly over-blown and over-sold. AWD is also significantly less capable in rough/uneven terrain than 4WD. However AWD can mostly be left on at all times, and is much more user-friendly and forgiving of mistakes than a 4-wheel-drive system.

For a great many people, especially people hoping to use their van off pavement, a RWD van with an aftermarket locking rear differential will provide vastly more capabilities than the factory AWD system.


4wd vs AWD

A 4-wheel-drive system mechanically locks the front and rear axles together, and the left and right wheels together if engaged with differential locks. This provides smooth, consistent power to all wheels no matter what is going on with the other wheels. This makes it much easier to maintain control and critically momentum when in challenging conditions.

AWD systems such as used on the Transit and the Sprinter don't have mechanical locks between the axles and wheels. Instead they use computerized controls to detect when a wheel is spinning and doesn't have enough traction, and then apply the brake to that wheel which forces torque to be sent to the other wheels. This video by CampoVans is a good example of how the AWD system works. At various points you’ll see an off-the-ground wheel spin, then stop. Or a wheel on the ground spins and skids, then stops. That’s the computer applying the brake to just the spinning wheel, so the other wheel maintains traction. Also note that the van will back the power off without the driver changing their foot position on the accelerator, making the van lose momentum and being more likely to get stuck.

The result is that while 4WD vehicles seem to glide smoothly through lose terrain and up hills, AWD vans tend to “hop” and lose momentum as the computer can't react quickly enough to sudden and abrupt changes in traction. This video from Quigly (who makes true 4WD systems for vans) shows the difference.

What AWD is good for

Daily driving and helping to accelerate on short sections of slippery, flat surfaces. Think of moderately plowed snowy streets, or pavement covered in wet leaves, or well graded gravel roads with short sections of loose surface. The sort of conditions that you might reasonably expect in daily driving in most daily-driving situations.

It's also good for drivers who have limited mechanical interest don't want to worry about how it works. AWD is pretty forgiving, while mistakes in application of a 4WD system will lead to immediate and catastrophic failures (And not failures like “Oh, a warning light came on”, but failures like “There was a massive bang and hundreds of shards of metal exploded out from underneath the van”).

What AWD is NOT good for

Rocky, rutted, bumpy or highly uneven terrain where wheels may temporarily lose contact with the ground. Or extended sections of deep, loose materials such as deep snow, sand, mud or very lose gravel where maintaining forward momentum is critical. In these situations the factory AWD system will frequently shut down if driven in such conditions for more than 1-2 minutes.

For situations such as these, a RWD van with an aftermarket locking rear differential will almost always out-perform the factory AWD system. See this video for an example of just how effective a locking differential can be!

Locking differentials can typically be installed into most RWD vans for $2-$3,000.

4-wheel-drive

4-wheel-drive conversions are offered by Quadvan or Quigly Vans. The Quigly 4WD system has been approved by Ford for the Transit, and if installed when new Ford will still honor the full factory warranty on all non-Quigly components of your van.

Expect to pay ~$15,000 to have a stock van converted to 4-wheel-drive.

rv/awd.1642238635.txt.gz · Last modified: 2022/01/15 04:23 by princess_fluffypants