1947-55 Tech Talk

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...

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...

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...

With the introduction of the Advance Design panel truck in mid 1947, it was soon evident that a serious safety hazard existed with a few companies, some night deliveries required the rear double doors to be open. This prevented the taillight from being seen! No doubt this caused some accidents particularly with a fast vehicle coming from behind, with dim...

  Beginning in 1951, the rear bumper became an option on both Chevrolet and GMC pickups. This required a change in the standard left tail light bracket. The tail light assembly was now unprotected without the bumper. GM created a new bracket design that brought the tail light slightly ahead of the rear edge of the stake pocket. In this...

  The Chevrolet and GMC left commercial taillight used during 1947-1953 is an excellent example of GM's conservative thinking towards trucks. The number one purpose for trucks was work! Therefore, if a part had been very successful on a prior body design, it just might be adapted later as a part in some new styling. Savings were in production costs...

A redesigned parklight assembly was started with the introduction of the 1947 GMC advanced body style. It was placed in the front fender 3-1/2 inches below the headlight ring. A 2-5/8 inch diameter bezel held a domed glass lens to its housing by two barrel screws. The unit was not meant to be a combination turn signal and parklight assembly...

  When viewing older GM cars and trucks we see both colors of park light lenses. There seems to be no consistency that gives us the proof of what is actually correct, however, it is easy as remembering a year. Beginning in 1963, the Department of Transportation new regulations required park lights to show an amber color, to be seen...

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...

  When observing restored 1947-1953 Advanced Design trucks, we rarely see the removable dash parts painted correctly. Though at least half the owners paint these parts to their personal taste, many truck restorers want the dash appearance as original. Surprisingly, we rarely see two alike even on trucks that are said to be restored just like they left the factory...

Between 1954 and 1959 the dash cluster of GMC trucks were given a circular opening for a dealer installed clock or tachometer. These trucks left the factory with a blank-out plate to fill this opening. With most GMC's this plate always remained in place as an option was rarely added. The enclosed photo shows both plates used during the period...

  Among the many updates in the new Advance Design body style in 1947, one that certainly stands out, is the change in gas tank positioning. For the first time since 1936 it was placed outside the cab and under the bed. The dimensions of this 16 gallon tank were based on the limited space between the right frame-rail and...

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...

  To help prevent metal to metal contact when 1/2 and 3/4 tons are overloaded or have weak shock absorbers, truck manufacturers used a rubber devise. This cushion prevents the axle from making direct contact with the frame rails. On the rear of the 1947-1953 GM pickups, it attaches directly to the underside of the hump in the frame. It...

  These are some very rare photos. It is quite unusual to find 1947-1953 Chevrolet and GMC 1/2 ton bare frames together. Here, you can compare the differences in the front cross members. As the GMC six cylinder is a few inches longer than the Chevrolet, engineers designed two different front engine cross members. In building the truck frame for...

  During the Advance Design years no less than four different Chevrolet hood side emblems were used on 1/2 tons. Each of their two mounting pins are in the same place so the punched hood holes were unchanged during these years. All were chromed die cast even during the 1952-1953 Korean war chrome shortage. The following pictures show the correct...

  As with many other items on the Advance Design Series trucks, there were also changes in the ignition switches. Both Chevrolet and GMC shared their several switch changes during the seven year series. In the beginning (1947-1948) a unique three position ignition cylinder and housing was introduced. This was a first for GM trucks. It related to a country...

  Both Chevrolet and GMC used the same steering wheel during the 1947-1953 Advance Design years. To keep the two makes just a little different the horn buttons had a separate design. Thus, the driver was always given a close view of the name of the truck he was driving. Chevrolet: Horn cap is chrome and then painted with steering...

During the 1947-1955 years, no less than four different front hood emblems were used during regular production on the Chevrolet 3000 series trucks. Though all can be made to interchange during this 7 1/2 year series; for the perfectionist, there are only certain types for certain years. In 1947, the 1/2, 3/4, and 1 ton Chevrolet trucks began production by displaying a...

Some trivia from Jim Carter Truck Parts: On the Advanced Design Pickups and larger trucks, the battery was under the passenger side of the cab floor. To protect the battery from road debris (gravel, sand and ice) it was important that it be protected from this coming from the right front tire. Designers of the Chevrolet and GMC installed the...

  These chrome hood ornaments were exclusively tooled for GMC trucks and have no similarity to the Chevrolet style. They are made up of three attached die cast pieces to create the finished product. Their slim base secures to the center of the hood divider strip. These were dealer installed GMC accessories. As trucks at that time were mostly for...

  By 1954, the Korean War shortages were history. More trim and chrome plating began to show up in trucks and cars. The Chevrolet and GMC truck divisions both introduced a deluxe model for their pickups during mid-year 1954. Hopes were to appeal to the emerging buyers with more disposable income. The deluxe model of these two trucks shared most...

  In the 1953 Chevrolet truck accessory book, there is a charging bull head displayed as an optional hood ornament. During my past 40 plus years in this hobby, I have heard reference toward this 1953 Chevrolet truck accessory hood ornament and have never seen an example or heard of another person seeing one. Does any reader have one? Has...

Between 1947-1953 the Chevrolet 1/2, 3/4, and 1 ton grilles were made from the same tooling. However, the paint colors and some with chrome plating made a difference. For the perfectionist, the following data will help you build a correct grille during your restoration. Painted Grilles 1947-1948 The standard grille has inner and outer bars the body color. Horizontally, a...

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...

  Installing the door weather seal on 1947-1955 G.M. trucks is not difficult, however some extra knowledge is required. Gluing it to the door edge incorrectly will limit its ability to seal drafts and add to wind noise. It is just as easy to attach this seal correctly. The design of correct weather seal is square on the bottom that...

  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...

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...

  During all of the 1947-1955 series, the five window cab, often referred to as the Deluxe cab, was available as an extra cost option. Their two corner windows helped in visibility especially when backing. Cabs made during the same year are identical except for these corner window options. Some buyers in the southern states rejected this option. They felt...

  An original drawing of a 1949 Chevrolet Suburban from their sales brochure. Shown with its rated seven passengers. NOTE: The lady driver emphasizes that it does not drive like a truck! (The hotel employee is probably wondering how he will place the suit cases and golf clubs in the space behind the third seat) Suburban Seating With the increased...

Yes, rubber pedal pads from 1947 through 1959 look the same when installed. However, because of the design of the metal pedal below them, they are different on their backside. Some suppliers market them as one item but the attached pictures will show this as not true.

  Over the years we have been asked 'Where can we locate the chassis frame for a Suburban or panel truck?' The answer is not complicated. To save much money General Motors used a modified frame from a pickup. The difference is four right angle brackets riveted to the frame. These provide an attaching point for the large single unit...

The very practical panel truck produced from the early 1920's through 1970 was an excellent cargo vehicle. Merchandise was protected from the weather and equally important from easy theft. Being a freight hauler, its cargo floor is like the pickup truck. Hard yellow pine and cross sills support the weight and merchandise slides on the metal strips.

Beginning in 1950, GM introduced an improvement in the cargo area of the panel truck and Canopy Express. It now followed the example of the Suburban by using a one piece, 5 ply floor. This replaced the planks that were always used in the pickup.

  Since their beginning in 1935, the Chevrolet Suburban was always the “people hauler” of General Motors commercial fleet of trucks. They were designed to carry more weight on rough roads than was the passenger car station wagon. While trucks were carrying freight from the time of their purchase, Suburban’s were reserved for passengers! It became an immediate success with...

A GM mistake on the 1947 Advance Design cab is the lack of a water drain on the top of the cowl. Heavy rains allowed water to run under the hood and down the firewall. No doubt some water damage would occur to the voltage regulator and the cloth covered wiring harness.

In 1952 GM made a simple change to the accelerator linkage that made a major reduction in engine noise in the cab. This was definitely an improvement when older engines had developed excessive valve train noise.

When your 1947-1955 GM truck needs rear cab corners and you prefer original US made replacement parts, there is an alternative.

Big Truck Deluxe Cab During the early Advance Design years of 1947-1950 (without wing vents) it is usually considered that a 5 window cab is all deluxe from the factory. The extras included stainless around the windshield and side windows, chrome grille, lower body color wheels with pinstripe, and right sunvisor and armrest. This is true on the 3000 series trucks; 1/2, 3/4, and 1 ton. An exception occurs on the 1 1/2 ton and 2 ton trucks. Though the cabs are the same as the smaller trucks, these deluxe cabs consisted of only the two corner windows. The Salesman's Data Book shows no reference to a chrome grille or window stainless. As money was tight and big trucks were all for work duties, it is assumed GM decided that the trim option would not be a good marketing item on the large vehicles. The corner windows were definitely a sellable extra. Visibility from these two additional windows helped much in backing. The lower photo is from an untouched 1947 Chevy 1 1/2 ton. The corner window cabs have no trim! Deluxe Small Truck (above) Deluxe Big Truck (above)

With the introduction of GM's new truck body design in mid 1947, a delivered package became available on both Chevrolet and GMC. World War II was in the past, employment was high, and many American truck buyers were willing to pay a little extra for more options on their new vehicle purchase.

During the first year of the Advance Design 1/2 and 3/4 ton pickup, the standard three speed transmission was a carryover from 1946. Its top loader shift lever extended directly from the transmission through the removable floor pan.

  The Chevrolet "Advance Design" gauge cluster looks much the same between 1947 and 1953, however a few differences do exist. For the perfectionist, these changes are important. In 1947-1948 the gauge needles are short (5/8 inches) and painted red. Between 1949-1953 the needles become longer (3/4 inches) and are white to match the change in the new speedometer needle...

  When looking closely at the black 1954 Chevrolet speedometer face, a small 1/8 inch diameter round hole will be noticed at the top and bottom. Owners of 1954 trucks will always be acquainted with the top hole. This emits red light to notify the driver that the high beams are on. Most are not even aware of the existence...

On first glance, most people assume that both Chevy and GMC gauge clusters are fully interchangeable and are the same except for perhaps the minor difference with Chevy oil gauges topping out at 30 psi versus GMC gauges maxing out at 60 psi. But that's quite a bit short of what the actual differences were originally! There are actually no...

  One of the numerous differences in the new 1947 Advance Design trucks is the different position of the mounting tabs on the speedometer. Reasons for doing this on both Chevrolet and GMC are as follows: with the introduction of this body style in mid-1947, both 3 and 4 speed transmissions were the floor shift design. However, in 1948 with...

Due to the abuse given trucks when they once considered only for work, many body components today are damaged beyond repair. During the restoration of your 1947-1955, if you would rather not use a running board splash apron from a parts supplier, there is an alternative. Locate a piece of new flat metal the correct gauge and size of your...

  The differences found on the cab during the beginning of the Advance Design years are subtle, yet on close study soon become quite evident. It probably exists on all vehicles when a body style is first introduced. Lab tests on a vehicle tend to overlook a few problems that later surface when it is in the hands of the...

From 1941 through 1953 the GM pickup bed sides are the same, however, a major design change began in 1954. This new bed side design with very few modifications continued to the end of the true step beds in 1987. The unique feature of only the 1954 through 1955 mid series bed sides is the flowing grooves that fit the...

During the Advance Design years the rear bumper braces on the 1/2 ton pickup are the same. Their cross section height is 1.75” and thickness is .35”. These units are designed with a rolling drop angle to lower the bumper to the proper level below the tailgate and rear cross sill.

During the early years of the Advance Design trucks there were many complaints by new owners about the rear bumper. They didn't want it as standard equipment. Farmers and businesses could not get close to a dock with a bumper and they removed them soon after the truck purchase.

During the 1947-1955 years, pickup's front and rear bumpers are different due to the shape of the body. Unfortunately, the front can be fit on the rear during restorations.

In 1954, GM introduced their new deeper improved stepbed. With this design the optional rear bumper required the license to be moved to the center. This eliminated clearance problems between the bumper and the left side mounted license plate.

The following article was released by GM on May 15, 1948. It was sent to all Chevrolet and GMC dealers and was to correct a problem with the location of the 1948 Brake release handle.

  Without the rubber covering over the metal running boards like GM cars, trucks immediately show scratches from the driver's shoes. This is frustrating to the restorer who has placed so much effort in repairing and painting these boards to pristine condition. Fortunately, a solution exists! The original running board safety treads have been reproduced. These treads were a GM...

  During the 1947-1955 Advance Design years three different stock running boards on pickups and panel trucks were produced. Features such as width, number of ribs, thickness of metal, and length of under-braces are the same. When placed together, a difference in length is obvious. The longest unit was used on the 1 ton pickup and panel trucks with 134...

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.

  One of the most unusual and rare options for the 1947-1955 1/2 tons are 'wide running boards'. The adjacent picture is from the 1949 Chevrolet Salesman's Data Book. The photos below are of used original boards recently found at an Oklahoma swap meet. They consist of 'short' running boards as used on all flatbed ¾ and 1 ton trucks...

In upgrading the Advance Design 1947-1953 cab for 1954, GM engineers created a totally different dash assembly. It required that the radio be much smaller. With better electronic technology and no push buttons, the new 6 volt radio could be placed into the smaller space. They even placed a cardboard sheet above the '54 radio to protect it from settling...

All 1954-1955 Chevrolet/GMC trucks came from the factory with a blank-out plate to cover where the radio would be installed. As this accessory was dealer installed the plate could be removed (probably thrown away) and the new radio added.   This blank-out plate and its two special clips has become very rare in recent years. They are not being reproduced...

  As more restorers become interested in the 1954-1955 Chevrolet truck, the demand for the correct factory accessories has increased demand. Trucks during these early years were used mostly for work and many owners ordered no accessories. Even the heater was often added later. Though locating a restored or restorable factory radio is a difficult task, there is another source...

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?

Stainless steel bedstrips are always a nice extra when you give your bedwood a clear finish. Not only do the strips look good but they retain this attractive appearance despite long term bad weather conditions.

During the Advance Design truck era, 1947-1955, most all spare tire assemblies were under the bed. Though not always convenient, this kept the extra tire away from the bed box and out of the way.

  For the Perfectionist During the first half of the Advance Design years (1947-1955), GM offered a special panel truck as an option. This deluxe model was designed for a company wanting to give a more upscale appearance to their retail customers. During the era of one car families, the lady of the house looked more toward home deliveries for...

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 the beginning of the Advance Design years (1947-1949) new Chevrolet Suburbans were sold in one color combination; Channel Green (light) on the lower body and Fathom green (dark) on the upper. Unless the customer paid extra for a specific paint such as for school bus use or a commercial paint color for a company, the two tone green was...

Since the introduction of GMC's first 1/2 ton pickup in 1936, there has always been a sharing of most sheet metal parts with Chevrolet trucks. This was done mostly for economic reasons. However, when possible, each of the two brands tried to make inexpensive changes to be different than the other. Some specific examples of this occurred during the Advance...

When observing un-restored GM trucks of the 1947-1955 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 trucks had been thought of as...

Purchasing a 1947-1955 optional cigarette lighter assembly from many vendors provides you a reproduction that is far from correct. It appears an overseas manufacturer decided to offer a lighter assembly made with the currently available 12 volt base and joining it to a 1947-1953 headlight knob.

  If you ever wondered about the color of the primer used by GM before the initial paint, these photos give the answer. This 1957 Chevy 1/2 ton had been polished through the paint in most areas. Of course, our question is: Why didn't they stop polishing when the primer first appeared.

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...