Mazda G35M-R / G66M-R

Mazda's G-series manual transaxles — the five-speed G35M-R and six-speed G66M-R — in the Mazda3 and Mazda6.

The suffix is a size, not a generation. The two appear in the same models in the same years, chosen by the engine, and a listing that says only manual covers both — which matters because their ratios, their clutches and their parts differ.

Their recurring failure is the input shaft bearing, and it announces itself the way every manual in this catalogue does: a whine present in neutral with the clutch out, which goes quiet when the pedal is pressed. Pressing the pedal unloads that exact bearing.

Shift quality complaints are the linkage, not the gearbox: cables and bushings wear and produce a long, vague change for a fraction of the cost of anything inside.

A crunch into second on a fast cold change is that synchro; a crunch into every gear is the clutch not releasing, which is hydraulic and outside the gearbox.