Electrical

1934-1946 GMC Tail Lights

Thursday, February 11th, 2010

Early GMC Tail Light

Though items were shared between GMC and Chevrolet trucks between 1936 and 1946, General Motors made sure many parts remained very different.  The GMC dealers preferred very few things to be similar to Chevrolet.  Their customers needed to see an almost stand-alone truck with the higher price they were paying.

One very obvious difference is the change in tail lights.  There is no comparison.  The massive GMC stamped one piece steel bracket combined with a redesigned 5-inch tail light makes the pair a “one-of-a-kind”.  They do not interchange with Chevrolet during those year.

It was not until the new body style in mid 1947 that the two brands shared tail lights. When the larger GMC’s 5-inch light was discontinued on trucks in 1947, Chevrolet introduced it on their 1949 through 1952 station wagons and early GMC buses. It was placed in the center of the gate and was the only factory light on the vehicle.

Even though 1936-1946 taillight was used for so many years, it is becoming very difficult to find. Most GMC pickup restorers use the reproduced Chevrolet rectangular design and only a few GMC perfectionists are aware that there is a difference.

A shop in the US is attempting to remake this bracket; however, if this happens the tail light will be almost as big of a project to find.  It is not being reproduced.

The photo below shows the real GMC tail light and bracket of the early years 1936-46 GMC.

1934-1946 GMC Tail Lights 1934-1946 GMC Tail Lights

Early Ignition Wire Protection

Thursday, February 11th, 2010

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, a metal wrap was placed around this electrical wire. See attached photos from a 1941-46 GM truck. A metal cap even covers the connection on the top of the coil for protection. It unsnaps to disconnect the ignition wire from the coil.

The cable system was very good 60 years ago, however, today it can create much frustration. The cotton insulation on the inside wire has deteriorated and pieces can drop away. In time the hidden wire gets exposed and may touch the outer metal cable causing a dead short. The engine stops with no notice. It may occur only on a rough road or during a fast turn. The engine may run well at idle or not run at all. One can imagine how difficult locating the problem can be. Opening the two ends of the cable and replacing the original wire may be good insurance. A modern vinyl covered wire will never be seen inside the original metal wrap.

Early Ignition Wire Protection 1

Early Ignition Wire Protection

1941-1946 Horn Parts

Thursday, February 11th, 2010

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 currently reproduced, including the upper bearing, rubber bumper, cap assembly, steering wheel, mast jacket, 3 finger horn cap retainer, and internal cap spring.

Note: Added are the available part numbers from the Jim Carter Parts Catalog.

Horn Contact Parts

Speed Up 6 Volt Starting

Thursday, February 11th, 2010

One of the more common reasons for slow engine turnover using an original six volt system is under size battery cables. Most of today’s auto parts stores only stock the smaller diameter 12 volt design. Unknowing owners mistakenly replace their original worn cables with shinny new ones that are as much as half the diameter as needed. Two ground cables are also required: One from the battery to the frame and one from a starter mounting bolt to the frame.

Six volt starters require twice the electrical flow to operate properly. Don’t blame your six volt system for slow unacceptable starter motor speed! Many restorers go to the expense of changing their 6 volt system to 12 volts. They feel their original system was inferior and believe what they did was necessary. The problem could have been corrected with just adding the three proper cables.

Remember: Millions of cars and trucks were made with 6 volt electrical systems each year. If they had not operated correctly they would have been built with 12 volt systems!

Battery Cables 6 Volt

Buy Parts for 1934 to 1946 Trucks

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