In January 1976 the W 114/115 series „Stroke Eight“ models were replaced by a totally reconstructed type range with the internal designation W 123. The model family ranged from the 2.0-liter 4-cylinder Diesel with 55 hp to the 2.8-liter 6-cylinder injection engine with 185 hp.
The new model range orientated itself to the S-Class which had been produced for three and a half years. Thus the new medium-size type was also provided with a semi-trailing arm rear axle which had already been introduced with the „Stroke Eight“ models. Furthermore it was equipped with a double-wishbone front suspension with zero steering-offset. The chassis sub-frame of the preceding models was not necessary any more. All other safety-related construction details realised for the first time in series 107 and 116 were of course transferred to the medium-size types. The most important improvements, in comparison to the preceding model range, was the even more stable security passenger cell with stiffened roof-frame structure, high-strength roof and door pillars as well as reinforced doors. The energy absorption of the front and rear deformation zone in the front and rear end was significantly increased by a controlled deformation capacity.
A technical novelty was the safety steering column, realised for the first time in series 123. Steering aggregate and steering column tube were linked together by a corrugated metal tube. In case of a crash, this corrugated metal tube could buckle to the side. This was a further step to reduce the danger of the column tube invading the interior of the car.
The various big round dual head lamps were a characteristic design of the new models. Next to the main head lamp, under a common lens, there was a smaller halogen fog lamp.