It was possible to change gears on ZIM much less often than on other domestic cars.


The large seven-seater sedan GAZ-12 was produced in 1950–1959. The car had a pre-war six-cylinder engine with a displacement of 3485 cmz and a capacity of 90 liters. with. (a similar one was mounted on the Emka modification and the GAZ-51 truck). By design, the ZIM was close to Victory, but an additional unit appeared in its transmission - a fluid coupling.

Instead of the usual flywheel, there was a drive or pump wheel on the engine crankshaft - half of a hollow ring with 48 blades. Driven - a turbine ring with 44 blades was mounted on the power transmission shaft. The host was integral with the hydraulic clutch cover, which was welded to the hub attached to the crankshaft flange. The clearance between the wheels was 3-4 mm. The power transmission shaft connected to the turbine wheel was sealed with an oil seal. To start the engine, a ring gear pressed onto the coupling casing was used.

The principle of operation was very simple. Imagine standing next to the included electric fan and the second impeller freely fixed on the axis - the latter will rotate the air flow. Similarly, the design of ZIM worked. Through a special hole, the casing was filled with turbine oil. Discarded by the pump wheel, it transmitted rotation to the turbine wheel. Between the clutch and gearbox was a conventional friction clutch. It was impossible to do without it, because the hydraulic system did not provide complete separation of the drive and driven shafts.

On ZIM it was easy to start from second gear, to ride in third - direct in a very wide speed range. Touching and shifting gears, the driver did not disturb passengers. Even the novice driver, thanks to the fluid coupling, threw the clutch without risking turning off the engine or causing the heavy sedan to jump. In this sense, the GAZ-12 was an ideal training car.

Of course, energy losses in the fluid coupling were inevitable. The turbine wheel always spun slower than the pump wheel, especially at a low crankshaft speed. However, at 3000 rpm, its speed was only 2–2.5% lower than that of the leader.

The fluid coupling rarely let drivers down. At many ZIMs, she has been working properly for more than a dozen years. This year, one of the surviving GAZ-12s of the 1950 edition successfully performed in the rally “2000 km in Germany” (ZR, 1999, No. 11).