Drive and RestoreThe Alfa Romeo transaxle explained: Alfetta, GTV6 and 75
From 1972 to the early 1990s, Alfa Romeo’s rear-wheel-drive saloons and coupés had an unusual layout: the engine at the front, but the gearbox, clutch and differential at the back. It is a big part of why those cars handle so well, and it brings a few specific maintenance points. Here is how the Alfa transaxle works.
The layout
In a conventional front-engined car the gearbox is bolted to the engine. In Alfa’s transaxle cars:
- the engine sits at the front;
- the clutch, gearbox and differential form one unit at the rear, the transaxle;
- a propshaft connects them, running at engine speed;
- the rear axle is a De Dion tube located by a Watt’s linkage, with inboard rear brakes mounted next to the differential;
- the front uses torsion-bar suspension.
Why Alfa did it
Moving the heavy gearbox to the rear brings the weight distribution close to 50/50, lowers the polar moment of inertia, and takes weight off the front wheels. The De Dion axle keeps the rear wheels upright and parallel while keeping the heavy differential and brakes off the moving suspension, reducing unsprung weight. Contemporary testers praised these cars as some of the best-handling saloons and coupés of their day.
The models
The layout arrived in 1972 with the Alfetta saloon, and the Alfetta GT coupé followed in 1974. It went on to underpin:
- the Alfetta GT, GTV and GTV6 coupés;
- the Giulietta of 1977 (type 116);
- the Alfa 90;
- the 75 (sold as the Milano in the USA), the last of the line, plus its derivatives.
The weak points
Because the propshaft spins at engine speed, a lot depends on it running true:
- Rubber couplings (“donuts”). The propshaft is split into sections joined by flexible rubber couplings. They age, crack and tear. A perished coupling causes vibration and, if it fails, can damage the propshaft or the transaxle. Inspect them regularly and replace them as a set.
- Propshaft alignment and support bearing. Vibration at speed often comes from worn couplings, a tired centre support or a propshaft out of alignment or balance.
- Gear linkage. The gearlever sits far from the gearbox, so the linkage is long. Worn bushes and joints give a vague, sloppy shift.
- Second-gear synchromesh. A commonly reported weak point, especially if the car is shifted quickly when cold. Warm the gearbox oil up before driving hard.
- Inboard rear brakes. Because they sit next to the differential, they are harder to reach than ordinary rear brakes. Discs, pads, calipers and the handbrake mechanism need attention that is often skipped.
- Leaks. Oil leaks from the transaxle seals can contaminate the inboard brakes, so fix them promptly.
Restoring a transaxle Alfa
When you work on the driveline, treat it as a system: couplings, centre support, propshaft balance and gearbox mounts all interact. Many “mysterious” vibrations on Alfettas, GTV6s and 75s disappear once all the rubber in the driveline has been renewed with correct parts.
Sources
- Wikipedia: Alfa Romeo Alfetta
- HotCars: the Alfa Romeo transaxle explained