Nissan RS6F51A / RS6F51H

Nissan's six-speed front-drive manual transaxle — the RS6F51H behind the QR25DE in the Sentra SE-R Spec V, and the RS6F51A in the front-drive Maxima.

⚑ It is not the FS6R31A, and the two are told apart by one letter. Nissan's codes carry the layout in the fourth character — F for a front-drive transaxle, W or R for a rear-drive gearbox — so the RS6F51 is a transaxle and the FS6R31A in the 370Z and the Pathfinder is not. The third character is the ratio count, which is why both of these are sixes. A parts listing that quotes one for the other is quoting a gearbox that will not bolt to the car.

The H is the limited-slip one. The Spec V's carries a Torsen differential and the Maxima's A does not, so they are not interchangeable as a unit even though the casing and the ratios read alike.

What owners meet is third-gear synchro wear on a hard-driven Spec V, and it is the ordinary consequence of a quick shift rather than a design fault. The clutch hydraulics are outside the gearbox and a crunch into every gear is theirs, not the synchros'.