In prototype form, as shown at the Earls Court Show in September 1974, the 400 tractor unit was powered by a Cummins NTC-335 but that power unit was not included in the engine options when production commenced, although some were built to customers’ special order. The show tractor was a special left-hand drive sleeper-cabbed unit, underlining Seddon Atkinson’s determination to expand its European sales. The company clearly had hopes of achieving greater market penetration promised by Britain’s EU membership.
When the range finally entered full production in the spring of 1975 the specifications were geared more to the UK market. Tractor units had design gross weights from 30 tons up to 37.4 tons, limited of course to (Seddon Atkinson 13-ton Hub Reduction) ‘Group’ axle. Instead, it had the Eaton 19220 two-speed 10-ton unit. At first the Eaton axle was released as an option to the Group axle but was soon made standard fitment.
