Mazda TK4 / TK5 (Toyo Kogyo)

The first manual gearboxes of the Ford Ranger, built by Toyo Kogyo — the name Mazda traded under until 1984, which is why a Ford truck of this era carries a marque nobody recognises stamped on its gearbox.

There are two of them and one is the other with a gear added. The TK4 is a fully synchronised four-speed with no overdrive, 1983 and 1984, in the 4×4 Rangers and the 1984 Bronco II: 3.96, 2.08, 1.39, 1.00. The TK5 uses the same four-speed core casting with an overdrive fifth assembly bolted to the back of the main case — 3.96, 2.07, 1.39, 1.00, 0.84 — and ran from 1983 to 1987 in both two- and four-wheel drive, and in the 1985–1987 Bronco II. The TK4 is the rare one.

Identify either by the bellhousing and the pan. The bellhousing is aluminium and cast as part of the case — it does not come off — and the bottom carries a ribbed, cast fourteen-bolt pan. The Mitsubishi FM units that followed have a removable bellhousing and a twelve-bolt stamped steel pan, which is the quickest way to tell which gearbox a first-generation Ranger actually has.

They take automatic transmission fluid — Mercon, or Type F on the TK4 — not gear oil. This is the single most consequential fact on the page. The Mitsubishi gearboxes that replaced them in the same truck take heavy gear oil, so the right fluid for a 1988 Ranger is the wrong fluid for a 1985 one, and both look identical from underneath.

The early cars used an external clutch slave cylinder, which is worth knowing before a non-releasing clutch is blamed on the gearbox.