Mitsubishi FM132 / FM145 / FM146

Mitsubishi's five-speed manual family, supplied to Ford for the first-generation Ranger and the Bronco II through the second half of the 1980s. All three members are five-speeds with a removable bellhousing and a twelve-bolt stamped steel bottom pan, which is how one is told apart from the Mazda M5OD that replaced it — that gearbox has an integral bellhousing.

They share one gear set: 3.769, 2.210, 1.516, 1.00 and 0.812. What separates them is drivetrain and case length.

• FM145 — the earliest, 1985 to 1987, four-wheel drive, behind the 2.8 and 2.9 V6 and the 2.3 Mitsubishi turbodiesel.
• FM146 — 1988 to 1992, four-wheel drive, a strengthened replacement for the FM145 behind the fuel-injected 2.9.
• FM132 — 1988 to 1992, two-wheel drive only, with the 2.9.

The FM145 and FM146 do not interchange, and the reason is an inch of case. The FM146's casting is roughly an inch longer. Fitting one where the other was means a different propshaft length and different transfer case linkage — so a used gearbox that bolts up is not the same thing as a used gearbox that fits.

They take heavy gear oil, which is worth stating plainly because the Toyo Kogyo units that preceded them in the same trucks and the Mazda unit that followed both take automatic transmission fluid. Three consecutive Ranger gearboxes, two fluid regimes — and getting it wrong is a slow, quiet failure rather than an obvious one.