Tremec T-56 / TR-6060

The six-speed manual behind almost every American performance car of the last thirty years — the Corvette, Camaro, Mustang, Viper, Challenger, the Cadillac CTS, ATS and CT5, and the Holden Commodore and Monaro.

The TR-6060 is the T-56's successor and is very widely referred to as a T-56, which is fair — it is the same architecture strengthened — but the two do not share their internals, so a parts listing that treats them as one gearbox will be wrong about ratios, synchros and the shifter.

Its characteristic complaints are about feel rather than failure. These gearboxes are notchy when cold and reluctant into second, which is normal; and they will refuse a fast 1–2 change on a light throttle because of skip-shift, a solenoid that forces first to fourth under gentle acceleration to meet an economy rule. That is a designed behaviour and not a fault, and it catches out a great many owners who go looking for a linkage problem.

When something does wear it is usually the shifter or the synchros, not the gears. A change that has gone vague is the isolator bushings; a crunch into third or fourth on a fast change is a synchro; a crunch in every gear is the clutch not releasing, which is a hydraulic problem outside the gearbox.