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in motor vehicles, a device for the unstressed and noiseless meshing of gears in the transmission of passenger automobiles and trucks. The action of a synchro-mesh is based on the prior equalization of the angular speeds of the transmission’s driven shaft and the gears attached to the driving shaft by means of friction between the engaged parts. A synchromesh consists of a carrier that slides along splines on the driven shaft and a sleeve connecting two friction rings with conical inner surfaces. The friction between the conical surfaces of the gear and the friction ring of the clutch equalizes the rotational speeds, after which the transmission is engaged without clashing.
The use of synchromesh for all speeds in a transmission (with the exception of reverse) provides easy engagement of the gears, eliminates the danger of chipping gear teeth, and lengthens the operating life of the transmission.