CHEVY TRUCKS
BUILT TO STAY TOUGH
The Chevrolet Advance-Design Trucks Of 1947-1954, Part II

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taken from the Light Commercial Vehicle Association (LCVA) - Mar/Apr 1984

We began our story of Chevrolet’s all new Advance-Design truck line in the Jan-Feb issue with a detailed description of the 1947 models.  In Part II we will follow the styling changes and mechanical improvements in this series year by year through 1954.

For 1948 all of the 1947 models were continued and one new model added bringing the total to 107 models.  The new model was the model 3742, a forward control Delivery Chassis.  We will get into a more detailed description of the Delivery chassis later.

For 1948 there were no exterior changes in the Chevrolet truck lineup.  The three series were continued from 1947, the Thriftmaster, the Loadmaster and the Cab-Over-Engine Loadmaster. Forester Green continued to be the standard color for all models except the Carryall suburban, whose standard color continued to be a two tone of Fathom Green and Channel Green.  All of the optional colors were carried over unchanged. The big news in 1948 for buyers of 1/2 ton and 3/4 ton 3100 and 3600 trucks was the change which put the shift lever on the column, for three speed transmission only, and the foot-operated parking brake.  The removal of the hand brake and gearshift levels from the floor area of series 3100 and 3600 trucks makes it easy for the driver to enter or leave through the right hand door.  Additional space was now available in Panel models for packages that were carried on the floor, and there was also more foot room for the third passenger in cab and Carryall Suburban models.

I think it is amusing that Chevy, Ford and Dodge during this time period placed the door lock on what they called the “curb side”.  Obviously, this was for driver safety so that he did not step into the street in front of oncoming traffic.  When I drive my 1952 Dodge I find it very inconvenient to exit from the Left walk around to the right, step up reach across the seat to lock the curb’s side door, back out again and lock the right hand door from the outside.  In theory, of course, the driver was expected to lock his door, slide across to the right and exit.  Sounds good, but doesn't’t work that way in real life.  If you have packages or other items on the seat or floor they are in your way and normally other passengers will get out and slam the door in your face.  Certainly placing the three speed shift lever on the column makes the floor less cluttered but how about all those buyers who needed and purchased the four speed trany?

In 1948 Chevrolet was the first of the volume manufactures to offer a 4-speed synchro-mesh, helical gear transmission as regular equipment.  It was an extra cost option.  As a result of this complete redesign, the 4-speed transmission case was wider, higher, and longer.  It was still of the same rigid, box-like cast iron construction as before. So that the new 4-speed transmission could be mounted interchangeably with the 3-speed transmission it was necessary to increase the length of the 3-speed transmission case and main shaft.  Minor changes were made to the dash and tow panels in that a new seal was added to accommodate the steering column, gearshift, and the transmission cases. The new foot operated parking brake was moved to the extreme left side of the cab.  A hand release rod was located just below the instrument panel. The foot operated parking brake offered a couple of advantages, it was easier to apply because more pressure can be applied with the leg and it helped to provide smooth starts on hill by allowing the driver to simultaneously accelerate the engine, engage the clutch, and release the parking brake lever.  Only a slight amount of effort was needed to release the parking brake because of an 8 to 1 mechanical advantage. A new left-hand inner fender skirt was provided to allow space for the pedal mounting lever.

The 1948 Chevrolet truck engine had some of the most significant changes made for many years to improve it’s durability.  Chevrolet’s policy was to continually make sure that it’s truck engines were fully capable of handling the extra heavy duty loads without sacrificing performance or durability.       Five changes were made in the 1948 Loadmaster engine, and were carried over to the Thriftmaster engine because of Chevrolet’s policy of adapting improvements to its entire line of trucks and of designing parts so that they were interchangeable whenever possible.  In the first table on the right are the changes made for 1948.

All of the engine-changes were common to both engine series.  In addition to these changes, on the Loadmaster series only the camshaft gears were changed to a more durable aluminum alloy material with a bonded steel hub.  This change was made only in the heavier duty engine because the heavy duty trucks supposedly operated under higher loads, thus were driven more in lower gear ratios resulting in more camshaft revolutions per mile.  It was thought that aluminum would wear longer than the fiber composition material it replaced. Except for the 3100 series and COE series, the oil filter opening was now provided on the top and to the front of the valve cover.  The 3100 series continued to use the same oil filter as the Chevrolet passenger cars.

Several mid-year [1948] changes were made to the 1947 models some of which affected the light duty trucks and they are listed in the second table on the right.

All 1947 tire options were continued for 1948, and for the 3100 series was added the 6.70-15-6 PR tire.  This new tire was an extra-low pressure type requiring 30 pounds, had a larger tire section and provided a greatly improved, softer ride.

The only new vehicle for 1948 was the model 3742.  Forward Control Delivery Chassis, and it had a wheelbase of 125 ½ inches.  Buyers could choose from a number of body builders to supply their body needs in nine or ten foot lengths.  Prior to the model 3742, when such bodies were mounted on Chevrolet chassis, the body manufacturer had to revamp a conventional chassis, at considerable expense to the customer.

The combination of the 3742 chassis with a custom body offered many advantages to the customer.  A large package load or bulky merchandise could easily be accommodated, the forward controls permitted easy access to the load from the drivers compartment.  The driver could work faster, with less effort, since the height of the body permitted him to walk in or out of the load compartment through side doors or rear doors.  Visibility was great because the large glass area and the higher sitting position of the driver permitted him to see more road ahead and to the sides of the vehicle.  The truck was also easy to drive due to it’s short wheel base turning and parking was easier.

The model 3742 was constructed basically from the 3600 series frame, but, the frame was extended both at the front and at the rear.  A heavier front axle I-beam as used on the heavier trucks was used to bring the front thread out by 4 ½ inches and to give the front axle more capacity to support the greater weight requirement because the engine and load were shifted further forward than in a conventional chassis.

The turning angles were increased thus reducing the turning diameter about 6 feet.

The front springs had to be heavier so the front springs from a 1946 Cab-Over-Engine model were used.  In addition, double-acting shock absorbers and a ride stabilizer were added as regular equipment.

The 216.5 cu. in. Thriftmaster engine was used with several modifications.  The carburetor from the COE model was used as well as a specially shaped air cleaner and a special oil filler pipe.

Since this type of vehicle was used in door-to-door service, where it would frequently stand with the engine idling for long periods of time, the windstream-operated, suction type of ventilator was not effective, so a new vacuum-operated closed type of ventilator was designed to fit this models requirements.  This vacuum-operated crankcase breather protected against sludge formation and oil dilution.

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1948 3104 1/2-ton Pick-up

1946

1948 6103 2-ton Chassis & Cab

2 ton

 

 

Engine Changes made in 1948

  1. New, precision interchangeable, thin-wall babitt main bearings for increased durability.

  2. The front, front intermediate, and rear intermediate bearing caps were modified to reduce bearing deflection and to achieve longer bearing life and greater overall engine durability.

  3. New thin-wall Babbitt connecting rod bearings for increased durability.  Connecting rod bearing metal was now the same thickness as the main bearings.

  4. The crankshaft was made heavier for greater durability.  The greater rigidity prevented crankshaft distortion, which caused bearings to wear unevenly and was also conducive to better engine smoothness.

  5. Chevrolet developed a new Buna “N”, synthetic rubber valve stem oil seal.  The advantages of the new design were to reduce the total weight of the moving parts, reduce valve spring surge, noise attributed to the rattling of warn valve springs was no longer possible as the covers were eliminated.  Service was simplified because all caps and seals were now alike.

 

Mid-Year Changes - 1948

  1. The inner front cab mounting bolts were eliminated as they were found to be superfluous and not needed on the 3100 and 3800 series cabs.

  2. A new, heavier front spring with eight leaves, and a rate of 315 lbs. per inch was used for all 3100 models.  The heavier springs resulted in less tendency to “bump through” on a rough road, and wheel tramp was eliminated.

  3. On the 4000 series the optional 6.17:1 rear end was made standard and the original standard 5.43:1 ratio became the optional ratio.

  4. The rear springs on 4100 and 4400 were beefed up and the over load was eliminated.

  5. The non-overfill battery caps was discontinued.

  6. The 15 inch wheel on the 3600 series was offset ______ in. more to provide more tie rod clearance.  The spare tire was also eliminated as a standard feature on the 3600 series.  The 3100 series was the only series provided with a spare tire as standard.

  7. The hood, body, and wheel paint color was changed to Cream Medium from Savory Cream


1947

1948 3805 1-ton Panel

1948 6408 2-ton Platform (stake bed)




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