General Motors Powerglide

General Motors' Powerglide — a two-speed automatic, and the first one the company sold in volume.

⚑ Two speeds is the whole character. It starts in a tall first gear and changes once, which is why a Powerglide car feels slow to accelerate and unbothered at speed — and why a complaint of it will not change down is usually the design rather than a fault. A reader expecting three or four ratios will report a gearbox that is working correctly.

It is simple enough to be almost unbreakable, which is why it outlived its own obsolescence: drag racing still uses it, because two gears means one shift and one shift means less lost time. Most current material about it is racing material, and a search for a road-car question returns build advice.

There are two families and they share little — the cast-iron original and the later aluminium unit. Establish which before ordering anything.

It is entirely hydraulic. Nothing is electronic, nothing can be interrogated, and diagnosis is pressure, fluid condition and the governor.