General Motors 4T60-E / 4T65-E

General Motors' transverse four-speed automatic — behind almost every front-wheel-drive GM car of the 1990s and 2000s, from the Century and Regal to the Impala, Malibu, Monte Carlo, Grand Prix, Aztek and the minivans.

Its ubiquity is why it carries the reputation. When people say a GM car of that period had transmission trouble, this is very often the unit they mean — not because it is unusually weak, but because there were so many of them and they were fitted to cars that were kept a long time.

The failure most owners meet is the 3–4 clutch pack. It wears, and the symptom is a slip or a flare on the change into overdrive that comes and goes with temperature before it becomes permanent. A 4T65-E that slips only when warm is that clutch pack, and catching it early is the difference between a rebuild and a replacement.

The pressure control solenoid and the input speed sensor account for most of the rest, and both produce symptoms far more alarming than their cost — harsh shifts, a limp mode locked in third, or a speedometer that drops out with the gearchange.

The 4T80-E is not a bigger 4T65-E. It was built for the Northstar V8 and shares neither parts nor procedures, so a listing that says only GM 4-speed automatic covers two units that do not interchange.