Corvette Speedometers . . . . .
The exciting thing about all Corvette speedometers when you first sit behind the wheel of a Corvette, is how high the speedometers read. In most cases, 160 miles per hour. Like all Corvette gauges and clocks, speedometers are broken down into groups (see below). Corvette speedometers for the years we are considering were all mechanical units. All of these units are basically the same mechanically with cosmetic changes over the years. The speedo cable is hooked up to the back of the unit which turns a rotating magnet. There is not a solid connection between the magnet and the speedo pointer itself. The magnet field produced by the magnet rotates a speed cup which is attached to the pointer. When speedometers are rebuilt, the head of the speedo is calibrated by charging or discharging the rotating magnet. The calibration is done on a precision machine dedicated to this purpose. The calibration of the speedometer to a specific Corvette, taking into consideration the tire size, rear end ratio,etc., is taken care of by a nylon drive gear in the transmission. The number of teeth on the drive gear will determine final calibration A note of CAUTION here. If you ever find an excess amount of heavy oil/grease in the speedo head, it is probably due to a worn nylon transmission drive gear allowing transmission oil/grease to travel up the cable into the head.. This has to be taken care of or the speedo rebuild job that you just paid good money for will go bad just a few thousand miles down the road.
1953 to 1957 - A beautiful chrome trimmed unit that sits right in front of the drivers line of site. In this group of years the speedo registered up to 140 miles per hour. These speedometers have in inner plastic lens with the dots and an outer lens with the MPH numbers. The chrome bezel and lens are available as reproduction parts. The speedo needle is unique to these years.
1958 to 1962 - This speedometer makes the jump up to the 160 mph mark. Also changed was the chrome bezel and moving the unit up in the drivers line of site to allow for tachometer to be placed directly under the speedometer. The plastic dial faces were also changed for these years. In '58 there was still a two piece lens like the '57 but is is different to fit this new speedo design. The '58 outer lens is the same thru '62 containing the mph numbers. It is available as a reproduction. In '58 there is an inner lens for the dots. This is not available as a reproduction but is normally in good condition and can be buffed out. The '58 speedo needle is different than the '59 to '62, having a longer shaft. From ''59 to '62 there is an inner dial painted black with the tick marks for the mph numbers. In '59 these tick marks were white and from '60 to '62 they were a pale green color. A lot of little changes to try and keep track of. The '58 to '62 chrome bezel is available as a reproduction. All speedos in these years had a screw on speedo cable.
1963 to 1967 - With the production of the new Sting Ray Corvette, a complete face lift was given to the instrument cluster. The tachometer and the speedometer were now large, the same size, and placed side by side in the drivers line of site. The speedos in this series are basically the same with some small mechanical differences. The '63/'64 are in a group as is the '65 thru '67. The cosmetic differences are in the type of face and needle used. The 63/64 tachs had a cast metal face with a deep cone insert in each face. The '63 having a brushed aluminum cone and the '64 having a semi-flat black ribbed cone. Because of this cone, the speed cup has a shorter shaft for the needle. So some of the internal parts are not interchangeable. The speedo needle was unique for these two years as it had a "bent" shape. The speedo face for the 65 thru 67 was made of flat sheet metal and the needle was a straight pointer. All of these speedos had a range from 0 to 160 mph. All speedos in these years had a screw on speedo cable.
A special optional speedo could be ordered on the '67 Corvette with an adjustable speed warning pointer. Set a moveable pointer to the desired speed and an alarm would sound when the speed was reached.
A note is made of the odometer rollers used for these years. It is very common for these odometers not to work as these speedometers work very hard to turn over both the trip and total odometer. There is a cross gear that usually wears out. The original numbers were applied with a decal which dry out, get brittle and flake off. The replacement odometers have engraved numbers.
1968 to 1977 - The "Shark Style" Corvette again made big changes in the instrument layout. Speedo & Tach were still side by side but some cosmetic and slight mechanical changes were made. The speedo still read from 0 to 160 mph but was in raised letters. The '68 thru '71 were a pale green color and from '72 to '77 where white. The needle changed its shape. GM was still basically using the same mechanical head from previous years. In 1969 the attachment of the speedo cable changed from a screw on to a clip/snap on type of cable.
1978 to 1982 - The "Dash Cluster" on this series of Corvettes changed.