I copy pasted the following from a recent post in the Paint and Body forum and did some editing too...
Differences include hood sheetmetal dimensions, engines, color variations, bed construction, electrical grounding, and frame front crossmembers:
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The cab is the same. But inside paint colors were different. The hood, grille, side curtains are different. fender extensions (upper fenders that transition to the grille and hood assembly) are the same. Chevy front and rear fenders same as GMC fenders.
Chevy hood is about 1.5 inches shorter. Has chrome horizontal bars on hood sides. GMC hood trim: chrome and black “General Motors Truck” hood spears.
Radiators have slight differences - each has its own radiator and surround. GMC mounting holes to radiator surround match the GMC radiator support. These are not the same as Chevy. Front grille lower gravel pans and lower bumper sheetmetal thingamabobs are different.
- GMC bed floors were steel. Chevy bed floors - southern yellow pine painted black. Tailgates are either Chevy or GMC script. Same with hubcaps.
(However, worth noting: 1939/40 rear fenders and running boards (whether Chevy or GMC) are wider. These will not fit.
1939/40 Cabs will fit however - the dash gauge clusters are different. Subtle difference with rear window mounting for the 1939-early 41 cabs. They have a steel window surround. Later version cabs have a rubber seal/gasket rear window installation.)
Dash gauge colors: dark brown for Chevy. Mustard yellow for GMC. Gauge bezel colors may be different.
Grilles: Art Deco horizontal grille bars for GMC. Vertical “waterfall “ Art Deco styling for Chevy.
GMC motors are about 1.5" longer than Chevy motors. Front crossmember's are also different between the two. Chevy crossmembers are flatter and GMC's have a more angular crossmember to fit the GMC radiator surround. This is more noticeable in the 47-54 trucks and more subtle in the 41-46.5 trucks.
Canadian manufactured GMC’s used Chevy 216’s and Chevy front crossmember frames. American manufacturing used GMC 228 engines with GMC front crossmember.
Front lights same but - they are different from the 1941 year to the 1946.5 years. I believe it has to do with the length or the upper light on these pods (can't remember
GMC’s 6 volt positive ground. Chevy 6V negative ground. (I may be corrected on this detail).
Heater badges delineated Chevy or GMC.
Bumpers: GMC front bumper does not have a center bumper bolt hole...Chevy bumper does.
Other than that load capacities, suspension systems are same. GVW’s maybe different due to steel bed floor for GMC trucks and variation in engine weight. . GM marketed the GMC line of trucks as a little more stout and sturdy than cousin Chevy.
GMC 228 engine design, pressure oiling and insert bearing systems was an improvement over splash oiling and Babbitt bearings in the Chevy engine.. Some would say the GMC head design was an improvement too. GMC engine color: olive green. Chevy 216 grey. Some GMC engines came from the factory with black paint too. It was the war years...I suspect material supplies became thin at various times.
Last edited by tom moore; 12/16/2020 7:58 AM.
