A brass or composite friction ring assembly inside a manual transmission that brings the speed of a free-wheeling gear to match the speed of the output shaft before the dog teeth engage. By applying friction ahead of mechanical engagement, it prevents the gears from grinding and allows for smooth, clash-free shifting without the need to double-clutch.
The transmission grinds going into third gear, which means the third gear synchronizer is worn out and we've to rebuild the box.
Using the wrong transmission fluid, especially one with friction modifiers meant for limited-slip differentials, can make synchronizers too slippery to grab, causing harsh shifting and rapid wear.
Also heard as
- synchro
- synchronizer ring
- baulk ring
Related terms
Manual transmission
A gearbox requiring the driver to manually select gear ratios using a shift lever and a clutch.
Gear shift
The lever and linkage assembly used by a driver to select transmission ratios.
Double-declutch
A manual shifting technique where the clutch is engaged in neutral between gears to match transmission speeds.
Clutch
The mechanical assembly that connects and disconnects the engine from the transmission.