T-5

The five-speed manual behind a generation of rear-drive American cars and small trucks — the Mustang, Firebird, Mercury Cougar, Chevrolet S-10 and Blazer, GMC Sonoma, and the Holden Commodore.

It changed owners twice and the catalogue's own rows show it: some say Borg-Warner T-5, some BorgWarner, some Tremec T-5. Borg-Warner designed it and Tremec bought the business, so all three name the same gearbox and none of them is wrong.

The distinction that does matter is World Class. From the mid-1980s the T-5 gained tapered roller bearings and carbon-fibre-lined synchro rings, and the two versions share very few internal parts — so the useful question about any T-5 is not who built it but which side of that change it falls on.

It is a light-duty gearbox behind engines people enlarge. Its torque rating is modest by the standards of what gets fitted in front of it, and the failure is almost always third gear — the cluster and its synchro — under exactly the abuse a modified car gives it. A T-5 that grinds into third under load is at the end of its rating rather than badly maintained.