WALKING TALL
The Coleman axle was a bruiser and a very unusual idea. Designed by Harleigh Holmes in the early 1920s, the patent for the design was filed in 1925 by him and granted in 1927. In that era, the hardest part of designing a steerable front axle was the knuckle. Transmitting power “around the corner” was not yet a perfected art. Instead of incorporating a universal or constant velocity joint into the axle shaft assembly, Holmes put it around the axle end. The very large hub covers on a Coleman axle protect what can be described as a gigantic universal joint that pivots around the axle end. Though big and complex, it worked as well as any other setup of the era and had a few advantages. The biggest problem was that it couldn’t be scaled down very much, so it’s always seen on larger trucks. Coleman put its smallest model onto light trucks from the late ’40s to the late ’50s and it didn’t work out very well. The axle weighed as much as the engine and it required very oddball wheels.
In tractors, the Coleman was apparently a good fit. The extra weight of the cast Coleman housing, with its Eaton-built pumpkin, was a welcome element. The output drive from the front axle was added into the range box of the final drive and a driveshaft led forward on the left side of the tractor. The Coleman kit could be ordered factory installed or for dealer installation, if an owner found a need for it after he had already bought the tractor. The axle could be swapped back to a row crop axle in about an hour and a loader could be used in conjunction with the FWA. One of the more interesting features is that the factory-installed kits used the “All-wheel Drive” emblem from the IH Scout 4x4 SUV on the cowl. There are some exceptions to this, of course.
The addition of the FWA allowed the 806 to put more of its high-for-the-era output into tractive effort. As the tractor manufacturers neared and reached 100 hp, they learned it was getting more difficult to maintain traction with only two tires. Bigger tires, more weight and duals helped. The addition of too much extra weight was counter-productive because it created compaction issues in certain types of ground, reducing yields. Dual remediated some of that but added a width and cost dimension in some venues. Better and bigger tires are usually a help but there’s only so far you can go in that direction. A driving front axle was a good answer and the preponderance of FWA tractors today is proof of concept.
A typical FWA has one major flaw: reduced turning radius versus a rear-drive unit. The wheel angularity of a driving front axle cannot be quite as tight as a dead 2wd axle, so the turning radius is reduced. This was more a problem with the old closed-knuckle GMC or Coleman axles than it is for the more modern open-knuckle axles, but it’s still a minor downside.
It’s probably worth a few words at this point to explain the difference between Front Wheel Assist (a.k.a., MFD, Mechanical Front Drive, or MFWD, Mechanical Front Wheel Drive) and Four Wheel Drive (FWD or 4wd). In tractors, it’s akin to the difference in light trucks and SUVS between full-time and part-time four-wheel drive. A FWA tractor has a driver control to engage the front axle.
THE 06 MODELS WERE A GENUINE TRIUMPH FOR IH AND THE NEW 806 LED THE CHARGE.
The Coleman axle used a specially made housing to which a standard set of Coleman knuckles was installed. It attached in the same places as the standard IH front axle, so it could be swapped as desired by the owner. The big giveaway for a Coleman are the huge domed hub covers. The differential was a standard Eaton unit similar to the types used in larger IH trucks, so there was other parts commonality within the IH divisions. The axle ratio, calculated to include the tire diameter, was just slightly higher than the rear so that the axle would pull instead of being pushed.