The Allis-Chalmers WD replaced the preceding WC model in 1948. It looked almost the same, but there were many improvements. The engine's compression ratio and RPM were increased. The power was rated at 36 hp in the USA, but only 27.5 hp in Europe. Alongside the gasoline version, versions running on kerosene and liquefied petroleum gas were offered. The dual clutch was quite advanced technology at this stage and made operation easier since the power take-off and hydraulics operated independently of the driving clutch. The power take-off clutch was oil-bath type and was operated by a hand lever. The brakes were now pedal-operated. The hydraulic lift was equipped with draft sensing. A special feature was the Power-shift rims, where the track width could be adjusted without lifting the tractor or turning the center disc, using curved rails welded to the rim. In 1952, a new constant mesh gearbox was introduced.

145,000 WD units were produced in six years. About twenty of these ended up in Finland. In 1953, a redesigned model, the WD45, was introduced. The displacement of the gasoline engine increased to 3.7 liters by lengthening the stroke. Power was also increased by raising the compression ratio from 4.5 to 6.45. A quick-attachment device, which became standard equipment, allowed the implement to be connected while sitting on the tractor seat.

In the early 1950s, Allis began looking for a diesel engine for its tractors. It ended up purchasing the Buda engine manufacturer in 1953. The WD45 Diesel was brought to market in the fall of 1954. The engine was a 3.8-liter 6-cylinder. The electrical system was 6 volts, but the diesel model had two batteries. The diesel model cost 40% more, and only 8% of WD45 buyers chose it. In 1956, power steering became an optional extra on the WD45. Over 90,000 WD45 units were sold.

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