VCCA Home Forums TECHNICAL - GENERAL Trucks and Vans 1956-57 GMC Horn(s)

The horns that are on my 56 GMC 100 Deluxe Cab sure look like they were born there, but a lot can happen in 60 years, and it's looking more and more like they are not in fact original to the truck.

They are Delco Remy 759 and 760, and they are the sea shell type with the round dome backing just like my 54 and 55.1 trucks. The 56 GMC maintenance manual, and the 55-57 GMC Master Parts Book both only list the number of one horn, the low note, which is for 56-57 and it's a 305, and the cross- section illustration in the manual looks to be the later type horn that does not have the dome backing cover... I assume then that the correct high note to match would probably be a 306. Can anyone with a 56 or 57 with an original horn, or preferably dual horns, confirm what they have in terms of model number, and if possible snap a picture of how it/they are mounted and what the brackets look like?

The Chevrolet parts books shows the 1955 and 1956 cars and trucks used the 759 and 760 horns.
I see no mention of a 305 and 306.That is from the 1957 parts book.

The 1959 Chevrolet parts book shows a 303 and a 304.
They changed horn parts number frequently back them making the horn kind of universal and coming as a kit with a detachable bracket.

I don't have a parts book that covers Chevy trucks in 56, but I do see from the diagrams in the assembly manual that 759 and 760 were used.

For GMC, since 55 models retained 6 Volts in 6 cylinder models, the horns are 641 and I would guess 642. V8 trucks were 12V across the board, and in 55 used 303 and 304. 56-57 are listed as using 305, and I assume 306, since the April 1957 GMC Parts Book I have does not list the high note horns. From the drawings I seein the maintenance manual, the 305, 306 horns appear to be the externally adjusted type.