WHAT IS 4-WHEEL DRIVE?
A 4-wheel drive vehicle doubles its tractive power by using another "powered axle" to drive the front wheels. It gets its tractive power not only from the two rear wheels, but from all four wheels -- all working together.
A conventional 2-wheel drive vehicle applies power to only the two rear wheels. The front wheels merely coast along, pushed by the driving thrust of the rear wheels.
In this way 4-wheel drive is therefore the means by which a vehicle's traction and its ability to move ahead or in reverse under extremely rough conditions is greatly increased.
THE 4-WHEEL DRIVE STORY
WHAT IS ITS PRINCIPLE?
A simple but clear example of the 4-wheel drive principle and its tractive comparison with 2-wheel drive is this:
A 2-wheel drive vehicle, like a man who naturally and normally moves around on his two feet, has only two points of driving contact with the ground for tractive power, i.e., the two "live" rear wheels.
When starting up a steep grade in 2-wheel drive, the "dead" front wheels are jammed or butted against the ground surface at the base of the hill. A short distance up the incline the rear wheels start to spin, the engine stalls, and the vehicle comes to a stop.
A 4-wheel drive vehicle, like a four-legged animal, has four points of driving contact with the ground. The front wheels as well as the rear wheels are pulling, driving the vehicle forward.
Starting up a steep grade in 4-wheel drive produces an entirely different result:
The front wheels pull the vehicle forward and up the hill -- parallel to the plane of the incline -- not into it, while the rear wheels are driving and pushing from behind.
This principle enables a 4 -wheel drive vehicle to take steep grades and pull through heavy going that will stall and stop ordinary reardrive-only automotive units.
MECHANICALLY SPEAKING, WHAT IS 4-WHEEL DRIVE?
First , let's see what 2-wheel drive is mechanically, and how it operates.
2-Wheel drive is made up of these assemblies:
A Standard Clutch
A Standard Transmission
A Drive Shaft to the Rear Axle
A Rear Axle and Differential
4-Wheel drive is made up of all of the above plus the following:
A transfer case behind the standard transmission
An extra front drive shaft with which to drive the front axle
Another powered axle and differential driving the front wheels
THE POWER FLOW
The first assembly to be considered is the --
It is of the smooth operating, dry disc type and has a torque capacity capable of handling all loads the Willys vehicle will be called upon to handle.
Second is the standard synchromesh transmission which provides three speeds forward and one reverse. This is normal in all 2-wheel drive vehicles as well as 4-wheel drive.
REAR DRIVE SHAFT
Next is the rear drive shaft. It receives power from the standard transmission through the transfer case and drives the rear axle.
Fourth in the power train is the semi-floating type rear axle. The load carrying capacity differs with each type of Willys vehicle according to wheelbase. The capacity is 4500 pounds on vehicles of 118-inch wheelbase; 3700 pounds on vehicles of 104-112 inch wheelbase; and 2500 pounds on vehicles of 80-inch wheelbase.
NOTE: It is at this point, that the mechanics of 4-wheel drive begin to differ from those of 2-wheel drive.
The transfer case is the fifth unit to be considered. Its 4-wheel drive lever serves to engage or disengage the front drive shaft, front axle, and front wheels.
In addition, the transfer case affords the operator a choice of high or low speed range or neutral when in 4-wheel drive by shifting the transfer lever. Essentially this is a 2-speed transmission. However, the low transfer range can be used only when the vehicle is in 4-wheel drive.
EXTRA FRONT DRIVE SHAFT
Sixth is the extra front drive shaft which delivers driving power to the front axle in the same manner as the rear drive shaft delivers power to the rear axle. In effect, it is a drive shaft placed in front of the transfer case to drive the front axle and front wheels. It has two universal joints of the same type as used in the rear - drive shaft.
Seventh, and last, is the front axle. Basically, this is another powered axle placed between the front wheels, complete with a differential as in the standard rear axle of a 2-wheel drive automobile.
From it the front wheels receive their motive power. The ends of this front axle are different from those of the rear axle in that there is a large ball joint enclosing a special universal joint at each end. This is known as a "constant speed" joint. This means that the front wheels can maintain constant speed at all times even on curves. No matter what the angle at which the joint is operating when the front wheels are turned to round a curve, the output shaft makes a complete revolution at the same speed as that of the input shaft.
WHY IS WILLYS 4-WHEEL DRIVE SO POPULAR?
Willys 4-wheel drive vehicles have gained great popularity among owners and operators all over the world because of their outstanding performance.
With the powerful, efficient, Hurricane and Super Hurricane engines, they do everything expected of 4-wheel drive vehicles, and do it better -- climb 60% grades under full load; travel over rough, off-the-road terrain and icy, slippery roads; and lug through sand, mud, snow and soft bottom land. They go almost anywhere. On the road -- off the road -- and in all kinds of weather.
But a Willys vehicle can do even more. Let's suppose the terrain ahead levels out, becomes easy to traverse. Perhaps it's a smooth, hard, dry road where loss of traction presents no problem. There's no need here for the extra traction of 4-wheel drive. Driving from the rear wheels only will supply ample power, speed, and tractive effort. Under these conditions the transfer case lever is pulled back into high range. The 4-wheel drive lever is pushed forward to disconnect the front-wheel drive and power is transmitted only to the two rear wheels.
This also serves to remove unnecessary strain from the drive shafts and universal joints and to reduce wear on the tires.
A Willys 4-wheel drive vehicle, then, is exceedingly versatile. It can apply the proper type of tractive power to any driving condition, on or off the road.
ADVANTAGES OF WILLYS 4-WHEEL DRIVE
We know the power of the engine can be transmitted through the transmission and transfer gear case to both front and rear axles. Traction can be applied to all four wheels at the same time.
What does this mean on --
When a slippery surface is encountered -- a slick, muddy or icy road, for instance -- the chance for wheel slippage or "spin stalling" is materially reduced. All four wheels are driving, pulling the vehicle forward.
The same principle holds true when rounding a curve on icy pavement, a slick, muddy road, or a freshly-oiled highway. A Willys 4-wheel drive vehicle reduces forward and side slip to a minimum because the tractive effort of the front wheels, working in harmony with the rear wheels, tends to pull the vehicle around the curve. This forward tractive action also makes steering easier, smoother, and more positive.
ROUGH TERRAIN IN HEAVY GOING
If snowy, muddy, or rocky terrain must be traversed, Willys 4-wheel drive again displays its ability to keep the vehicle moving forward under conditions that would stall a 2-wheel drive unit. All four wheels literally get down and "lug". There are no loafers under a Willys vehicle. Each wheel is doing its own particular job, carrying its own weight under its own particular corner of the vehicle.
In hilly country where steep grades must be negotiated, the Willys 4-wheel drive principle shows up to distinct advantage. It can drive a vehicle up a 60% incline under full capacity load! At the base of a sharp grade the front wheels are not jammed or butted against the ground surface as in the case of a 2-wheel drive motor car. The front wheels, upon contacting the base of a steep hill, literally pull their way up the grade while the rear wheels are pushing from behind. Each of the four wheels supplies a power-driven point of contact with the ground surface. This i s translated into tractive power at all four corners of the vehicle.
The same positive tractive power that takes a Willys 4-wheel drive vehicle over practically any terrain, or through any heavy ground surface condition, also gives it an added margin of safety in descending dangerously steep grades -- grades that cannot be negotiated safely by a vehicle of conventional 2-wheel drive design. The operator simply shifts to low-low (low gear in the transmission, low position in the transfer case) and permits the vehicle to roll slowly down hill with all four wheels turning against the compression of the engine. The engine supplies a firm, even braking power. The four wheels, with their axles locked firmly in their differentials, supply the tractive power against the ground surface. These are the safety margin factors that keep the vehicle from "running away" and permit the operator to retain steering control.
WHEN DOES THE WILLYS 4-WHEEL DRIVE PERFORM AT ITS BEST?
Any Willys 4-wheel drive vehicle performs at its best when the going is toughest. Because it can go anywhere and everywhere, a Willys vehicle -- whether it be the Universal 'Jeep', 'Jeep' Station Wagon, 'Jeep' Truck, 'Jeep' Sedan Delivery, or any other unit in the 4-wheel drive line -- takes all jobs in stride just as naturally as it travels along a super highway or across rough terrain where roads are non-existent.
A Willys 4-wheel drive vehicle has an unlimited number of applications. For a sample list, see the "Applications" Section.
THE PROOF IS IN THE PERFORMANCE
Once a prospective customer gets behind the wheel of a Willys vehicle and feels the lifting, pushing, pulling, driving power of 4-wheel drive at his command, he will immediately think of the many uses to which he can put it -- on his farm, his ranch, in his business, in the industry in which he is employed.
THE WILLYS 4-WHEEL DRIVE IS DESIGNED AND BUILT TO PERFORM AND TRAVEL OVER DIFFICULT TERRAIN, UNDER ANY DRIVING CONDITIONS, AND IN ANY KIND OF WEATHER. THIS IS TRULY "TRACTION IN ACTION'' !