Honda S20 / S4C

Honda's five-speed manual transaxle codes — in the Civic of the 1990s and early 2000s.

Honda's transmission codes are stamped on the case and are the only reliable way to identify one, because the same model year offers several and the parts differ. S20, S4C, S40 and their relatives look identical from outside — and the S24A of the same cars is not a manual at all, but the four-speed automatic, which has its own page here. A listing that says only 5-speed manual on a Civic of these years settles nothing.

These gearboxes are durable and their faults are the faults of hard use. The third-gear synchro goes first on a car driven quickly, then the gear; and on the higher-output engines the differential and its bearings are what the torque finds.

A crunch into every gear is the clutch not releasing, which is hydraulic and outside the gearbox.

They take Honda's MTF, not a gear oil and not ATF, and a conventional 80W-90 makes one notchy when cold and hard into second. That symptom has now appeared on eight gearboxes across eight marques in this catalogue, and it is never the synchros.