4wd terms

Locking diffs simply put power to both wheels on the same axle regardless of whether you are in full time or part time. In part time it will send power to both back wheels and then also power to whatever front wheel is slipping most. In full time, if the rear two tires that are locked start to spin, the front axle may get no power at all. Full time lets your front and rear axles turn at different rates. Lockers get you unstuck, or in some cases, more stuck. KH

The term Open Diffs has NOTHING to do with 4LO, or 4HI for that matter.

An open diff sends equal amounts of power to both tires until one of them begins to slip, then that wheel gets all of the power. The other wheel that still has traction gets no power, and the vehicle is stuck.

A Limited slip also sends equal power to both wheels until one begins to slip, then it send the power to the other wheel that still has traction.

A locker sends equal power to both wheels all of the time, regardless of which wheel has traction ans which is slipping.

Full- and Part Time 4WD has to do with the tcase. The differentials divide the power from left to right on the axle, the tcase divides the power from front to rear. The tcase is not able to divide the power in a part time system, but it can in a full time system. What happens is, when the vehicle goes around a corner, the front and the rear travel remarkably different paths, the front is generally a longer path than the rear. Since the time to trave the paths is essentially the same, then the speeds must be different, and the tcase must hav ethe ability to privide for these different speeds. A part time case can not do this, a full time case can. A full time 4WD system is roughly equivelent to an All Wheel Drive system, but not really.

Incorrect. If only one wheel on either axel is driving the vehicle, then it would get really squirrelly while you accelerate.

It's only when a wheel looses traction that it SEEMS like only one wheel is driven. Not correct, though.

Technically this is not true. Open differentials are in the vast majority of cars on the road today. Limited slip is on sports type cars, and lockers are only available on a very limited number of offroad vehicles, and some new pick up trucks.

Actually, it is absolutely correct. It not only SEEMS like only one wheel is getting power, it is fact that only one wheel is getting power when it loses traction.

One thing to remember about open differentials... and this is not just a rumor or something that I made up... no matter what is happening, whether either wheel has good traction, poor traction, or one wheel has good traction and the other has zero traction... both wheels always always always (!!!) receive exactly (!!!) the same power to them. The power is ALWAYS split 50:50 between the left and right wheel on an open axle. Ok now you're saying bullshit... but it's true, really. What happens is that when one wheel starts spinning and has no traction, the axle starts spinning the tire that has the least amount of traction which then presents the engine with little or no resistance to work into. With no resistance to work into, the amount of torque produced drops down to nearly nothing. That "nearly nothing" amount of torque is split 50:50 by the open axle (again, really)... which is enough torque to spin the tire with little or no traction available to it, but not enough to spin the tire that still has traction.

So limited slips do not "send power" anywhere, they act by friction or by gearing to couple the spinning tire to the one with traction to present more resistance to the engine... with more resistance felt by the engine, the amount of torque it sends to the rear axle is increased. That additional torque is still split 50:50 but may now be enough to get the tire with good traction to begin moving the vehicle again.

So it's a basic fact that both wheels are indeed (really...) getting a 50:50 split of the power being sent to it via the driveshaft. Whether that 50:50 split provides enough torque to the wheel with good traction decides whether you move or not.

So all this is why the old trick invented back in Model T days of applying the brakes when you're stuck really does work. It causes the engine to see more resistance so it develops more torque when the tires can't provide enough resistance themselves and start spinning.

Jerry

That brake trick works excellently too!

For some reason, the rear drum brakes seem to transfer the torque easier than the front disks, so it is easier to get both back tires spinning than all 4 spinning though I have managed a 4 rooster tail take off a couple times.

Mike

Jerry Bransford wrote:

And adjusted so that one or two clicks will get you going.

Another thing that will keep you out of trouble in the winter is a small engine, but most of you guys aren't smart enough for that. ;o)

Earle

Earl:

My 1960 VW Bug had a small, 36 hp engine, but that didn't keep me out of trouble when I was a teenager.

:)

Tom

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