The Fiat 66 series was a smaller and more affordable alternative to the 80 series. The external dimensions were significantly more compact, but there was hardly any compromise on the technology. The lifting capacity and hydraulic output were on par with the more expensive series, the brakes were oil-immersed, and the four-wheel drive model featured hydrostatic steering. The transmission was fully synchronized, even before the smallest models of the 80 series, and a 1000 rpm speed was also available on the power take-off. The cab was simple, but according to the factory, the noise level did not exceed 82 decibels. An optional sun canopy was available for the cab.

Initially, the transmission was 12+4 or, with crawling gears, 20+8. From 1984 onwards, a 12+12 shuttle shift transmission was also available. The 466 model was also available with a partially synchronized 12+3 transmission. The four-wheel drive option included a central axle, but a differential lock on the front axle was standard only on the 666. The technical relatives of the 66 series were similarly powered models from Agrifull, acquired by Fiat.

In 1984, the 766 was introduced with the engine from the 780, featuring a lifting capacity of 3580 kg.

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