Posted by Paul Cook on Wednesday, October 02, 2002 at 4:07PM :
In Reply to: wc 6x6 vs ffpw with 44x18.5x16.1 D. Higgins? posted by lokin for floation ? on Wednesday, October 02, 2002 at 9:23AM :
There have been several people on this and Forum #76 interested in the cross-country performance of the WC-62/63. Obviously these folks have been seduced by the WC-62/63's appearance of having unlimited traction because of the extra tires on the ground. I waited for other WC-62/63 owners to respond about their driving experiences. None did so here goes.
The 6x6 was initially developed from the WC-51/52 ¾ ton 4x4 Weapons Carrier to provide additional capacity to carry an infantry squad whose size was increased to include a crew served weapon. Three major changes make the difference. The bed length increased from 6 to 10 feet. A "bogie" rear suspension carried a second rear axle that increased the GVWR 3000 pounds. And a two-speed transfer case with a 1.5: 1 low range was added. Each rear axle is driven by its own drive shaft from the rear of the transfer case. This rear drive set up was similar to the drive shaft splitter set up on the larger Dodge tandem axle trucks.
The WC-62/63 does not have a particular advantage over its 4x4 counterpart in low traction situations. The driveline design limits the available traction. Neither the front nor the rear axles have anti-slip differentials. The front and both rear drive shafts are geared together and all turn at the same speed. When one wheel on any axle begins to slip, the other two axles pick up the load. This increases the work each remaining axle must do. When the wheel on another axle begins to slip, the entire traction load goes to the remaining axle. If a wheel on that last axle begins to slip, then no power is transmitted to a wheel with traction. This is usually the case in mud, snow, and ice. The six wheels have reasonably good results in sand and soft dirt if the driver can maintain momentum. There may be occasions when both sides of one of the three axles may have traction but a wheel following a wheel into a place with no traction will also lose traction.
Another factor that limits traction is the tires. The early WC Dodge military trucks used a directional tread tire that looked something like a tractor tire. One of my WC-63's came with a well-worn directional tire as the spare. The problem with directional tires is that they are too directional. A directional tire may have 150% more traction in its primary rotation than a non-directional tire, but have only 50% as much traction rotating the opposite way. If all your tires were mounted to favor moving forward, you might not be able to back out of a low traction situation. This led to numerous command directives on how these tires should be mounted. The most common procedure was to mount the front tires "backwards" so you could back out of a bad spot - assuming you hadn't driven in too far. Other procedures required all tires to be mounted so you could "power through" - which often meant you got stuck much worse. This is the reason the military adopted the Military Non-Directional Tread tire.
The Military Non-Directional Tread (NDT) tire was developed as a compromise of several characteristics. The continuous center rib helped carry the load on pavement and hard dirt. The ribs distributed the load in soft going and the "paddle" design gave traction in either direction. The directional tire did one thing best. The non-directional tire did many things but did not excel in any. As a result, available NDT's do not provide the two things that help a truck going in low traction situations - plenty of tread bite and lots of flotation to keep the truck from sinking into soft ground, sand, snow, and mud.
As a result, the stock WC-62/63 performs poorly in low/no traction situations. I've been unable to pull a moderately steep hill on wet grass. When the truck is carrying no additional weight, the load on each rear tire is so low that the tires don't have enough ground pressure to get traction. When the rear axles have no traction, it isn't long until one of the front wheels loses its grip and starts spinning. I've had the same problem on surfaces with loose dirt and stones. Add a load to get some weight on the rear axles and that "bogie" suspension acts like it is on rails and it now takes a couple acres to turn around.
The 6x6 was developed to provide a large bed and increased weight carrying capacity. It performs well on established off road trails and improved roads. It just isn't that great going cross-country.
There's not a lot than can be done to make it better. The rear axles are 42 inches apart. That means that tires with an outside diameter of 42 inches would touch. I haven't tried mounting my 38-inch Swampers but standing them next to the stock tires makes them look like a very close fit where any mud on one tire would be dragging on the mud of the other tire. I don't think there are many tires that will help because of the distance between the rear axles. I have plenty of tire clearance with those Swampers on my FFPW's and the ¾ ton military Dodges.
If you need to haul a load that two axles cannot handle, you might want to look into a surplus M-35 deuce-and-a-half. Good ones with low mileage are available for less than a Power Wagon in the same condition.
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