Abstract: A gearbox drive that adapts the drive train ratios of vehicles to standard speedometers, including an input gear, an intermediate gear and an output gear rotatable about axes defining an equilateral triangle, arranged so that upon rotation of the input shaft in either direction, the reaction forces on the intermediate gear will be substantially balanced. The gears are supported in mating cup-shaped input and output gear cases with the input gear case member having an input gear bearing and two secondary bearings each of which selectively supports either the intermediate gear or the output gear. The output gear case member has an output gear bearing and two secondary bearings each of which selectively supports either the intermediate gear or the input gear.

Abstract: A vehicular instrument or gauge of the type that has a sealed housing filled with an inert gas and a pressure responsive drive assembly for an indicating element such as a needle pointer. The housing is provided with a pressure relief valve to relieve excessive pressure within the housing that includes an inwardly facing integral frusto-conical projection with a central aperture in the back of the housing that receives a valve member which is actually a rivet covered by a flexible adhesive such as silicone rubber. The amount of adhesive and the housing wall area covered by adhesive determine, with the diameter of the head of the rivet, the pressure at which the rivet will be blown from the housing relieving internal pressure.