A Closer Look… Chevrolet G-506 1-1/2-ton trucks

As a person who has used WWII Chevrolet military trucks for almost half a century and who is currently still using them, I read a feature in the August 2008, issue of Military Vehicles Magazine (no. 128) about the trucks. It is nice to see information being made available about one of the handiest military trucks ever produced. As the article indicated, civilians quickly found the size and performance of the trucks to be exactly what met their needs after the war. Because of that, thousands of them are still in use today, more than sixty years later.

For those who are unfamiliar with the trucks, there are several things that can be added to what was originally presented in the MVM article. A couple of corrections are also in order because without them future writers who consult the article may pass on erroneous information to future generations. Maybe in the overall scheme of things small details may not seem important, but those of us who really like the old Chevys do care.

CLOSER LOOK AT AXLES

For a long time it has been generally thought, like GMCs, WWII Chevrolet trucks came with both split differential axles and banjo axles. If one considers prototypes, that may be true. However, no production G-506s ever had split axles.

Timken, the manufacturer of the split axles, found that it did not have the capacity to produce enough of its axles to meet the military’s needs. There were two reasons for that. First, as a component supplier, Timken’s production facilities were based on normal demand from civilian truck manufacturers. When war came, its ability to increase production was limited even though it did produce thousands more axles than its factories were originally designed to build.

The second reason is that Timken axles were machined to exact tolerances and were designed for great durability and high speed service. Roller bearings were used throughout and provision was made for adjustments that would be needed for extended use. The only weakness the axles had was a tendency for the differential cases to spring when a truck was greatly overloaded. When that happened, they leaked oil from the joint where the two parts of the axle housing bolted together.

When the military wanted Chevrolet to build 1-1/2 ton 4x4 trucks, there were not enough axles to go around. That was especially true of the powered front axles. At the government’s request, General Motors (both Chevrolets and GMCs were GM products) developed a new axle for Chevrolets and any GMCs for which Timken could not supply axles.

Those axles have a round pumpkin shaped differential that has cast reinforcements in the cover. The shape resulted in them being called “banjo axles.” Although actually stronger than “split axles” in weight carrying capacity, they weren’t built to the close tolerances used by Timken.

Instead of roller bearings the banjos used ball bearings. The result was that all banjo axles were a little bit crude. That is not an indictment, however, because they did the job when needed and have proven to be durable for more than half a century.

The disadvantages of banjo axles include higher unsprung weight and the inability to stand up to continual high speed use. Since few banjo-equipped trucks were used in that manner by the military (the Red Ball Express and other similar operations required fast long haul operations but were of short duration), the banjo axle trucks faithfully soldiered on long after their military service ended.

All early GMCs were split axle-equipped. All Chevrolets were banjo-equipped. Later GMCs were a mixture of split and banjo. Unfortunately, the photo previously published as a G-506 actually showed a GMC. Even though the two trucks looked very similar from the front, the unique spring shackles were used only on GMCs. Also, the heavy, wide-tie bar behind the grille bars which fasten the front edge of the front fenders together is only found on GMCs

OUTWARD APPEARANCE

Speaking of similar appearance, it is obvious that closed cab GMCs and closed cab Chevrolets shared the GM corporate cab. After 1943, GMCs were built with open cabs but Chevrolets continued throughout the war with the closed cab. It should be mentioned that a small number of open cab G-506s were built as bomb service trucks but they are rarely seen today. Not only do they lack the hard cab, but they are built on a significantly shorter wheelbase. Chevrolet fitted these with banjo axles as well.

Even though some think GMC and late G-506 grilles were “virtually identical,” that is true only if viewed from a distance. There was no difference in shape, but a major difference in construction. Whereas the GMC had flat vertical bars with tabs bent top and bottom and welded into the frame (the tabs on those bars were welded one direction early in the war and another direction on later models), Chevrolet bars were round.

Early trucks had bars looped top and bottom and welded just inside the front edge of the grille surround. Later trucks still had round bars but they were individual and welded on the front edge of the grille surround so they stuck out from the surround. Almost all Chevrolets had symmetrical headlight/black-out light guards. Black-out drive lights, if equipped, were mounted on the top of the driver’s side guard.

The Chevrolet 1-1/2-ton truck used engine side panels with six louvers instead of the twelve found on its GMC 2-1/2-ton big brother. Early GMCs had a small name plate welded to the center of its grille. G-506s had “Chevrolet” stamped into the front two-thirds of the engine side panels. Of course, after the military decreed that company names could no longer be visible on the exterior of vehicles, neither truck had any identification other than on the nomenclature plates fastened inside. Many civilian owners discarded the side panels because they made servicing the engine more difficult. Thus, they are somewhat hard to find today. The embossed “Chevrolet” panels are particularly in demand because even late model truck owners like to have the manufacturer’s name displayed.

A unique feature of G-506s is the mounting of winches which were found on some trucks. For some reason, the Chevrolet frame stops about where the radiator sits. A frame extension was riveted to the main frame on all trucks so that the front spring front shackles were attached to it and not the main frame itself. If the truck was winch-equipped, the sub-frame was much longer and both the spring shackles and winch sit out front. If a person would like to add a winch to a G-506, the rivets that hold that short sub frame can be cut off and the longer sub frame installed.

Chevrolet cargo trucks had nine-foot beds whereas most GMC cargo trucks had twelve-footers. During the war, both the all-wood and metal beds with wooden floors were produced. Today, wood beds are almost non-existent. Original metal beds are also very hard to find not only because civilian owners often cut the sides off but also because the Chevrolet bed was made out of lighter metal than the GMC version. Nice twelve-foot beds are tough to find, but the nine-footers are even more so because they rusted out more rapidly. Even in the driest parts of western America, finding a Chevy bed without rusted out stake sockets is rare.

A warning is necessary here to anyone considering buying a Chevrolet G-506 that appears to have the original military bed. About three times as many GMCs were built during the war. Because of that, GMC parts are much more plentiful. That applies to truck beds as well. Due to the shortage of Chevrolet nine-foot beds, it was common practice for many years to take a late GMC twelve-foot steel bed with a wooden floor and cut it down to fit the smaller truck. It was a simple job for anyone with ordinary welding skills and it is difficult to tell the finished product has been modified. The way to make sure your truck has a real Chevrolet bed is to examine how far the bed extends outside the short steel sideboards. The Chevrolet bed has wide extensions and are easily walked on. GMC beds have short extensions and even though they can be walked on, it is difficult to do.

PUT ’EM TO WORK

As a work truck, the Chevrolet 1-1/2-ton excels. Although the GMC CCKW received all the accolades during the war, the Chevrolet is a much better truck for civilian use. Its shorter bed can still carry a decent load.

Driving a G-506 is a more pleasant experience for two reasons: One, its smaller size makes it easier to maneuver. Secondly, loaded to its carrying capacity it is easier to steer, accelerates faster, and generally feels well balanced. The feeling of extreme inertia that all WWII tandem axle trucks have is missing. Yes, its inline six-cylinder doesn’t have as much horsepower as the GMC, but when driving one, it feels like it has more power per pound of vehicle and load than the larger truck does.

For military vehicle enthusiasts who aren’t interested in Jeeps or Dodges, the Chevrolet truck is ideal. It has the feel of a big truck without the inherent disadvantages. Although it uses expensive 7.50x20 tires, it only requires seven (spare included) instead of eleven (spare included) that tandem axle trucks do. It is short enough to fit into a suburban garage. If the garage door is only seven-feet high as most of them are, it is necessary to deflate the tires some to lower the truck down enough to get it inside. A person can live with that.

Licensing requirements vary with states but some allow owners of trucks larger than pickups to license them for only part of a year. Waiting until early summer when the weather is decent to buy a license cuts down on the cost.

Since almost all Chevrolets are closed cabs, it is possible to drive them in the winter if a personnel heater is added. The closed cab seat is adequate in comfort and the noise level inside is reasonable. Larger trucks with a five-speed overdrive transmissions are noted for extreme gear noise that is not only unpleasant but increases the fatigue factor a great deal.

DON’T WORRY ABOUT PARTS

For a long time, replacement seals for banjo axles were next to impossible to get. Recently I have seen seals listed as available but they are expensive. Since the trucks are 60+ years old and most have been used hard by civilians, plan on having to do some major work on the running gear.

Fortunately parts for the tried-and-true 235-cubic- inch Chevrolet six-cylinder engine are readily available should it need repairs.

Basic cab parts are available through old civilian Chevy truck sources. All glass is flat and is available from most glass suppliers if you can provide a pattern for them to use for cutting it.

The hydrovac brake booster has been, until recently, a problem because it usually needs repair and parts and service are lacking. Thankfully, there are currently manufactured boosters that can be substituted and that work as well or better than the originals. They tend to be expensive, however.

If you would like to have a G-506, try looking in any farming area close to where you live. Although farm trucks often lead a hard life, since they are used seasonally they usually are in better condition that those used by construction companies, etc. where they were used year round. Rust is a problem in humid areas but in Western America most trucks are rust free or almost. The lower parts of the door and the rear corners of the cab are the places most susceptible. Patch panels for those areas are available from civilian sources. Running boards take a beating and replacements are hard to find.

But overall, old Chevy trucks are very capable survivors of the great events of World War II.