1934-46 Tech Talk

General Motors was coming out of the wire wheel era by 1936. This as well as wood spokes had been a standard with most cars and light trucks since the beginning at the turn of the century. The new stamped steel wheels on Chevrolet 1/2 tons were easier to produce, and was less susceptible to side damage on rough terrain...

During the early years, most roads were not paved and the quality of tires was far from that of today. Thus, tire repair was very big business. It was necessary for vehicle manufacturers to provide the easiest access to the often needed spare tire. Part of driving a car or truck was knowing how to change a tire. On the...

GM trucks titled prior to the mid-1950's were usually registered using the stamped engine number not the body digits pressed in the door ID plate. This practice has created many problems in later years as states became stricter in titling. Unfortunately, many older vehicles outlast their engine and owners rarely rebuild the originals. To save time and certainly expense, a...

On 1937-55 1/2 and 3/4 ton rear bumpers there exists an unused center square bumper bolt hole that sometimes brings up questions from restorers. "Why does this hole exist and what is it purpose?" The answer relates to the attitude toward trucks during those years. They were for work and keeping their production cost low was a priority. The bumpers...

Of the many differences between the Chevrolet and GMC 1/2 ton during the early years (1936-54), the GMC offering of a long bed pickup box was one of the more noticeable. Only GMC provided this option. To obtain this extra bed length on a Chevrolet, the buyer ordered a 3/4 ton. This difference existed with the first GMC pickup in...

When you would like to restore your truck and no workshop is available, there is a solution. Most all the repairs can occur in a temporary shop and at a very low cost. Jim Valano of Marion, Indiana is a true example of 'American Ingenuity.' He purchased a 'canvas storage tent' and assembled it at a convenient location. He even...

Prior to the mid-1930's, the two truck divisions of General Motors, Chevrolet and GMC, were mostly independent companies. If you wanted a 1-1/2 ton and smaller truck, Chevrolet (since 1918) could provide the model just right for your needs. If you needed a 2-ton and larger, GMC was the division to contact. They had been a large truck specialist even...

Even before the 1920's, light commercial hauling using panel trucks had found a loyal growing customer base. With increasing numbers of small businesses and the population gradually moving to the cities, the panel truck found a place in our society. By the 1930's, most all truck manufacturers had designed a panel body to fit on their existing pickup truck chassis...

It's the height of World War II. The Japanese have control of the rubber plantations in Indonesia. The few tires available are reserved for military use.  And, the rationing of gasoline stops most U.S. vehicle operation.  But, there were still trucks needed on farms, keeping telephone lines operational, and supplying store commodities for their city.  For these selected truck uses, new tires could...

General Motors right hand drive trucks, though unusual in the United States, have always been very popular in specific countries such as Britain, New Zealand, South Africa, and Australia. These vehicles were not produced in the U.S. but came from GM's large assembly plant in Oshawa, Ontario. Due to reversed dash boards, the change in steering components, differences in starter...

Keeping the passenger area warm in cars and trucks during the winter was always a problem in the early years. Not only were the heater fans and cores small but the vehicles used recirculator heaters. Thus, the air in the cab was recirculated rather than using dry outside cold air being brought inside and warmed. This helped for quicker warming...

The Australian 1937-38 Chevrolet trucks are much like those in the U.S., however on close observation, one can certainly see unique differences. This United States relative is obviously GM but not quite the same. These Down-Under truck's final assembly point was in the Holden plant in New South Wales, Australia. (Holden is a branch for GM in that country.) Much...

During the great depression of the 1930's, almost half of the automakers ceased business forever. Most remaining manufacturers modified their vehicles and advertising techniques to appeal to a very conservative buyer. With limited disposable income the few people willing to purchase a car or truck were very careful. To help boost or at least hold sales steady, the Chevrolet Division...

1934-1946 Chevy Truck Model I.D. We hope the following information on Axle, Transmission and Model identification will help many of you with your questions. Accuracy was a concern as we compiled this information. Because GM made so many scheduled as well as unscheduled changes, there is much discussion about these changes. The following is used by permission from Pickups and...

1918-33 Chevy Truck Model I.D. We hope the following information on Axle, Transmission and Model identification will help many of you with your questions. Accuracy was a concern as we compiled this information. Because GM made so many scheduled as well as unscheduled changes, there is much discussion about these changes. The following is used by permission from Pickups and...

The body I.D. plate - every GM truck had one attached at the factory. Basically it states the vehicle's gross weight limit (weight of truck plus its maximum allowed load) plus stamped digits that give the assembly plant year, size of truck, month built, and sequential numbers as it came off the production line. These plates are necessary for positive...

Jim Carter Truck Parts viewed so many older salvage yards to find so much of this data by accident! It was just there! There couldn't be an easier place for a tree to grow. If you don't move your truck for a few years, trees will find it. As they grow wider, the truck bends to fit! Here livestock cannot...

Prior to the 1960's, trucks were used as work vehicles. On Friday nights, most were parked for the weekend and the family sedan was the transportation vehicle. It was a conservative era when you bought only basic necessities. A $5.00 grocery purchase was more than most could carry. Finding white wall tires on a truck (even a car) would have...

When you need more room for wider 8 bolt non-split rim wheels on your stock 1946-1959 Chevrolet or GMC ¾ ton, there is a solution. (The long tie rod ends prevent the use of wheels much wider than the original split rims.) Customers have given us an answer! It is not difficult and uses all original GM parts. After the...

At the beginning years of the 216 engine (1937-1938) the fan blade that cooled the radiator was made with a center hub plus four blades. Each blade was attached to the hub with three rivets. This combination worked well when new, however, it was certainly more expensive to produce. A dangerous part of the design was the blades attached by...

During the 1930's and 1940's most of our Nation's roads were dirt and gravel. Paving had been underway for many years but there was still a long way to go. To protect engine components from a constant attack of dirt, GM designed metal stamped panels that attached to an area where the engine block and oil pan connect. This slowed...

During the 1936-37-38 years of this cab design, subtle changes occurred as GM engineers learned better ways to construct this truck. The gas tank changes on the pickup body style was probably the most obvious and it was different each of the three years. In 1936, the new mid year low cab pickup continued with the earlier practice of securing...

Though the major cab and fender sheet metal change began in mid -1947 (Advance Design), both the Chevrolet and GMC trucks kept their same proven six cylinder engines as used in prior years. The base engine in GMC light trucks was the 228 cubic inch inline six cylinder introduced in 1939. This overhead valve unit had a full pressure oil system...

Occasionally we hear owners condemning the closed drive shaft system used in the 1/2 ton trucks prior to 1955. After questioning the negative comment, we almost always discover the real criticism is the low gearing of the ring and pinion in the differential. Yes, this lower gear ratio was created more for slower roads of year gone by, but it...

And now we've seen it all! A real example of American ingenuity. Designed by an aftermarket company to keep an over tightened valve cover from leaking motor oil down the engine sides.  A metal band is pushed over and around the base of the valve cover.  Brass U-brackets are then secured by the two valve cover studs.  This creates equal...

Rebuilding the 1937 and older pressure plate can be a little tricky. The early design (activated with a carbon throw out bearing under pressure) requires extra steps when being rebuilt. With the help of an older shop manual (see below) the final details can be successful. The personal letter is from Richard Wright of Westtown, NY. He did not receive...

Chevrolet introduced their basic nine inch single disc clutch and corresponding diaphragm pressure plate in 1938. This pair was used in their cars and most 1/2 ton pickups with three speed transmissions through 1953. With about one million of these vehicles sold annually, one can quickly realize the high numbers of this clutch system that was at one time on...

The door window is cranked up tight in the cloth channel and off you go on your daily errands. Suddenly, the glass begins to slowly lower as you drive over side roads or contact a rough surface. In comes cold air, rain, and wind! Even the window handle turns. What's this all about? Do you tape the window closed or...

Even if you prefer an original vacuum wiper motor for these years rebuildable cores have become very rare and most New Old Stock units are just not obtainable. Even new ones have their lubrication dry after 70 years. For those that won't accept a slow moving or non-working used vacuum unit, an alternative does exist. New electric motors are now...

During the early years of auto and truck design, most vehicles came with their windshields capable of tipping outward. This helped poorly insulated cabs to be more bearable during hot weather. Extra outside air would be forced into the cab and replaced some of the hot air radiating from the bare sheet metal firewall. This idea was good but not...

During 1939-40 Door window breakage on truck cabs became a problem. As the cloth fabric in the door window channel became worn, the large and now loose fitting side windows were susceptible to cracking when the door was slammed. Complaints from dealers resulted in an improvement on 1941-46 doors. A one piece metal frame was placed around the edges of...

Prior to about the mid 1950's, motor oil did not have the modern detergent additive we have today.  Therefore this type engine oil didn't keep dirt particles in suspension. Foreign material would slowly settle to the bottom of the oil pan and on other flat surfaces such as the valley of the head. If you ever removed an oil pan...

Prior to about 1962, Chevrolet trucks were equipped with round straight through mufflers. These units reduced back pressure and allowed the engine to breathe to its full potential. This caused a little extra exhaust noise in comparison to the larger more engineered oval car mufflers but trucks were for work and power. About 1950 truck mufflers were given slightly larger...

The Problem The closed drive shaft ( on GM 1/2 ton, 1937-54) is supported at the front by two bushings. As these wear egg shaped over many miles, the drive shaft begins to move up and down. This ruins the grease seal and causes the u-joint to begin rubbing the "bell" that covers it. Thus noise and vibration! Finally, with...

Before the modern Positive Crankcase Ventilating System (PCV) most automotive engines breathed externally and removed their excess products of combustion into the atmosphere. It was a standard of the industry! The lower end of the engine (below the piston rings) had an attached draft tube that extended outside and below the block. It released blow-by from worn piston rings and...

For Chevrolet Trucks 1929-47, and autos 1929-38. Should last the life of the truck! Remove unit. Remove the four bolts on the transmission tower plate. Knock out the old worn or broken bushing from the tower, install MET136 and add grease. Adding the large replacement tension spring will insure a snug fit. Problem: Slop in the shift pattern on 1947...

The term artillery wheel is a nickname adapted from a scalloped type wheel often seen on US military vehicles in World War I. The similar appearance at a distance to GM's scalloped steel wheels quickly gave them the name artillery. On GM trucks, this style was first used during 1934-36 as a stock six bolt 1/2 ton 17 inch wheel...

About 10 years after the introduction of GMC's new inline six cylinder engine in 1939, General Motors issued a 'Product Service Bulletin' in regards to a recommended improvement on the 228, 248, and 270. It appears the manufacturer discovered a weakness that shortened the life of the engine timing gears. This recommendation was made for enlarging the oil supply hole...

From 1934 to 1959 GM 1/2 tons came from the factory with a tie rod assembly that extended side to side to almost touch the front wheels. With everything stock, the tie rod sits about 3/4 inch from the inside of both original six hole wheels and all fits just right. A problem exists when someone attempts to add a...

If you use a recently manufactured 216 water pump and combine it with the optional larger OEM radiator fan, a slight modification is necessary. The fan rivets will not clear the edge of the pulley hub. You must cut four notches in the hub for rivet clearance. Water pumps in the last five years appear to lack these notches. Note...

Sometimes overlooked by mechanics and restorers is a small vent in the rear axle housing. This part is necessary to keep internal pressure equal to the outside atmosphere. Thus, as the internal temperature of the differential warms during use, any expanding heated air is vented and no pressure occurs. This saves wheel and pinion seals from leaking. Check for this...

One series of the famous "drop out" GM differentials was used between 1946 and 1972 on 3/4 and 1 tons. The complete assembly (often called a pumpkin) will interchange during these years with no alteration. The highest gearing in this series is the 4.10 ratio and is found in most 1967-72 3/4 tons with automatic transmissions. Therefore, those "low gear...

Locating a pair of seat cushions for the 1939-46 truck has become very difficult in recent years. These early trucks increased popularity is the main reason for the shortage. Even when a pair of cushions are located the asking price often does not justify the purchase because of the age damage to the springs and frame of the lower cushion...

The introduction of factory sealed beam headlights came to the automotive industry in 1940. It was then necessary to create park light assemblies. (They could no longer be incorporated in the bulb and reflector style headlight as before). To some, the first 1940 GM assemblies were simply "add-ons", maybe a quick design due to the fast industry acceptance of the...

Jim Carter Truck Parts seat cover kits are produced with an emphasis on originality. The materials are top quality for many years’ service. Seams, ribbing, etc., are based on original seats. We recommend that installation be done by a professional upholstery company. However, if you wish to do it yourself, here are several important steps to follow: 1. Seat springs...

Two major changes occurred in 6 volt General Motors sealed beam bulbs (are actually not sealed beams) since they were first installed on vehicle assembly lines in 1940. The perfectionist restoring his truck to exact original specifications must have the correct headlights for his year. In very competitive judging, it’s these details that can make a difference. No doubt, replacement...

Four Speed Backup Light Switch - They Did Exist! The first design of the 4-speed synchronized truck transmission, introduced in 1948, was used through about 1965. About mid series, when the dealer installed backup light increased in popularity, a special switch was attached to the base of the floor shift lever. This was the only location possible as there is...

On most all early GM trucks their fuel line exited on the bottom of the tank. It was usually attached to a brass shut-off valve which threaded into the tank. In case of fuel pump or line repair, a person had to lay under the truck to turn the tank valve and stop fuel flow. No doubt, this design resulted...

What's this bad rap some people give the GM pickups with in-cab gas tanks? For 35 years GM protected these tanks from collisions by double wall reinforced cab metal, doors, and seat riser frames. The 1937-46 pickups even secured the tank under the seat and surrounded it on three sides by the welded to floor heavy gauge metal seat riser...

During 1941-46 a unique device was used in the front of both frame rails of Chevrolet/GMC trucks. It was designed to serve two purposes. This forged steel 'horn' was a spring hanger as well as a connection for front bumper braces. These horns are securely riveted into the end of the frame and were designed to last for the life...

During the 1930s and 1940s many auto and truck manufacturers protected the long ignition wire between the dash switch to the coil beside the engine. The technology of wire insulation wrap during these early years was a woven cotton covering and it was more susceptible to damage from oil and antifreeze in the engine compartment. For protection, the cloth covered...

  One of the more asked questions on the 1941-46 GM trucks is regarding horn contact parts. Most have been damaged over the years and new owners are unsure how they were originally assembled. Below, is a diagram from a 1940's GM Master Parts Catalog and gives an excellent view of the parts used in the assembly. Most items are...

The big news for GMC in 1936 was the introduction of their first 1/2 ton pickup. Though GMC shared cabs with Chevrolet trucks, the visual exterior differences were mostly noticeable in front of the hood. The GMC grill was totally redesigned and did not resemble the Chevrolet truck. This unique grill was modified little between 1936 through 1938 but the...

Shortages during this major war was the reason for many modifications of Chevrolet and GMC door handles. War demands for die cast material changed handle designs on military trucks as well as the few commercial vehicles bought by civilians. The attached photos show these war time designs. The exterior handles have a stamped steel outer cover. Their inner liner is...

The unusual side doors on these Suburban and Panel trucks will fit on the more common pickup cab, however, their looks will tell the observer that something is not correct. Across the top of the outer skin is a horizontal stamping or groove. This groove is a continuation of the stamping that runs the length of the body to help...

Many of the tech articles on this web site emphasis's the subtle ways that truck parts were made economically by GM. Truck often received Chevrolet car items that were used the year before. Sometimes even other GM brands sent their older items to be placed on assembly line trucks. Of all the ways GM saved money on truck parts, none...

Early GMC trucks changed their hood side emblems about as much as Chevrolet, however there is no similarity in appearance. The following shows the GMC changes over 14 years. 1935-36   Anodized silver aluminum with a semi-flat black background. (In 1936, GMC entered the light truck market and carried the emblem from larger trucks of earlier year) Right and left are the same...

The mystery of where to find and replace the rubber door bumper cushions on 1934-46 GM trucks is solved by the following data: During many restorations these bumpers are neglected or the owner doesn't even know where these small units are hidden. They cannot be seen unless the inner cab sheet metal panel at the rear door post is removed...

Companies outside the Chevrolet Motor Division have always produced replacement parts for the aftermarket industry. Manufacturers often begin reproducing non-original parts very soon after a new vehicle is introduced. A problem occurs on decorative trim such as hub caps. Here, Chevrolet (and other manufacturers), display their logo to attract positive attention. To reproduce a Chevrolet hub cap, non-GM companies have...

The two series of exterior door handles on GM trucks between the years 1934-46 are certainly different yet they share a few similar features of interest. One characteristic which seems strange today is that the handles lock the right doors only, not on the left. This occurs on GM trucks from the early 1920's to about 1959. At this time...

  Leaf spring width on 1/2 ton pickups remained at 1 3/4 inches until the introduction of the two inch width on the Task Force 1/2 tons in mid 1955. The early narrow springs worked well considering the engine horsepower and weight limitations of the 1/2 tons. The two inch springs became standard equipment on the rear of the 3/4...

The straight axle ½ ton GM pickups (1959 and older) were built tough! They served their purpose as the best in work vehicles for over 30 years. Other than an occasional kingpin replacement, they were almost 'bullet proof'. In today's world, the reasons for owning an older truck, has generally changed. Most have been retired from work responsibilities and have...

Early Shock Absorbers Trucks of the Advanced Design years were often exposed to the rough terrain of local gravel roads as well as the dirt ruts on the farm. Quality, long life shock absorbers were a necessity. Therefore, this series of trucks in 1947-49 continued with a proven design of shocks carried over from the earlier vehicles. The highly successful...

Mechanical components on trucks were usually kept for many years by GM. Unless an improvement was needed, there was no need to change a proven design. An excellent example of this is the rear ½ ton axle bumper. The design was used from 1929 through 1946 on Chevrolet and GMC ½ tons. A rubber bumper is held down on the...

With the US entry into World War II, trucks were quickly modified to be successful for military use. Pre-existing cabs, frames, and mechanical components were altered to be more usable when in everyday work duties or in battle.

During the war years, the US was plagued with a shortage of rubber. The Japanese occupied most of the islands that grew rubber producing plants. The majority of the rubber the U.S. could obtain was sent to the war effort.

Maybe the rubber was of lesser quality. Maybe the GM truck division was saving money. For some reason Chevrolet and GMC trucks were not designed for rubber brake and clutch pads.

The United States and its allies suffered from major rubber shortages during World War II as the Japanese had control of most Indonesian rubber tree plantations. To survive without this material, much of the world was forced to settle on a limited supply of synthetic rubber of lesser quality.

In designing the panel truck, engineers realized that this vehicle must have a bumper for body protection. This bumper however, created a slight problem! It held the person loading freight further away from the vehicle cargo floor. He was required to lean further forward to reach merchandise. To help solve this problem, GM modified the standard bumper to come closer...

Gauges in Chevrolet truck dash panels during the mid through late 1930’s are very similar and are spaced, from each other, almost the same. Even their smaller chrome gauge rings interchange. The 1934-35 gauges are in the middle of the dash and there is no glove box. The 1936-39 instruments are centered above the steering column with the glove box on the right side.

A unique feature on GM truck cabs became standard equipment between 1940 and 1946. Before and after this, truck cabs were very basic. As they were made for work, almost no extras were on them. The idea was to keep manufacturing cost very low. There was much competition with other makes trying to also keep their sale price as low as possible.

There is none! Truck cabs during these early years all came the same from the factory. Accessories were dealer installed. You picked the factory installed color and the dealership added requested extras such as heater or inside sunvisor.

Some beginners tend to place 1936-46 cabs in the same category. Don't do this! The 1936-38 and 1939-46 are a totally different design. Very little interchanges. The early style provided excellent building blocks for the new design 1939-46 trucks.

Did you ever wonder why the 1934-46 GM trucks show major rust on their horizontal flat sheet metal? The mystery is solved! These pictures show without a doubt what a wonderful home Chevy and GMC trucks provide for field mice. After the truck has been abandoned at the edge of a pasture, placed in a salvage yard, or just stored...

This early glove box lock assembly has a weak point that makes it difficult to find complete. Its die-cast vertical pointer is held in place by a small steel tension spring. After the truck sets outside abandon several years the spring rusts, breaks, or otherwise looses its tension. This allows the pointer to fall out and the glove box lid will no longer stay closed.

It is quite surprising to realize that for 20 years auto and truck makers did not make a simple needed change to their vehicle front fenders. Somehow major car and truck companies picked 1936 as the year it would be introduced. Did they all get together and make the decision, was it government encouragement, or ____? The addition was side...

It is so unusual to find an unmolested mid 30s truck! When this all original 21,000 mile 1937 GMC appeared at a recent New England truck show, we had to take notice having never seen the correct installation of the small 3/8” bead cab windlace on an early model. Our camera did some recording.

The rubber quality on Pre-World War II vehicles was fair at best. Its useful life was limited. Thus, GM engineers did not add rubber pedal pads to early trucks. They were aware of the heavy abuse so many commercial vehicles would receive.

Since the introduction of hydraulic brakes on trucks in 1936, Chevrolet and GMC had been using the Huck brake system. On light trucks and cars it can easily be identified by the existence of a pair of shoe adjusting holes in each backing plate.

Using a specialized gauge to show wear levels on brake drums is the best way to indicate wear, however there is a visual method.

The common practice of replacing the original differential with a newer high speed assembly usually brings up another question: How do I connect the late model brake cable to the original brake system?

In 1940, GM began offering a slightly wider bed on their Chevrolet pickups. This width increased from about 46 3/8" to 48 1/2".

Though Chevrolet and GMC were usually close in their construction during the 1940's, they were far apart in a few areas. GMC in particular advertised some of their major differences as being steps above the competition.

Prior to 1941 in GM pickups, the bed wood of choice was oak. The change to yellow pine occurred at this time and it was used until the end of the wood bed floors in 1987. This southern yellow pine is a hard wood and should not be confused with softer white pine.

During 1940-46 the Chevrolet GMC trucks came standard with an unusual interior paint. It added a little extra appearance with minimum extra expense. This has been referred to as "Hammered Paint". While drying this paint develops a fish eye appearance. This helped make up just a small amount for no cloth door panels or related extras found on GM cars. After...

In evaluating the available paint colors on 1946 and older GM commercial vehicles, one should keep in mind the general attitude toward pickups and large trucks during that era. Unlike today, customers bought and owned trucks for work! After five o'clock and on weekends most trucks were parked and the family sedan became the driver. This relates not only to...

After seventy years, authentic car and truck restorations are very difficult. With the limited survival of the 1936 GMC (the year of the company's first ½ ton) this truck is especially difficult to restore just right. Some literature has survived but what we see is usually in black and white. The question is the grill housing color of this rare...

Serious early truck restorers often ask 'What is the interior color of the original cab sheet metal parts, versus the exterior color?' The answer for the 1934-46 trucks is simple. The removable panels from the cab interior were always the inside color. If a component was welded in as part of the cab structure, it was sprayed the exterior color...

When observing un-restored GM trucks of the 1930-55 era, one will notice the majority of these vehicles were originally dark green. An explanation is simple. Green was their standard color! If you did not specify one of the other approximately eleven non-extra cost colors, your truck would be delivered green. The standard color of truck had been thought of as...

The following article used by permission of the writer: Robert Hensel, Technical Advisor Coordinator for the Vintage Chevrolet Club of America.  Bob passed away several years ago but his GM truck certainly lives on! I do not know of any book that gives the engine colors for all Chevrolets. I have found it here and there in many Chevrolet letters...