| In spring 1971, another serial sports car was presented with the 350_SL type, replacing the 280_SL, which had been built since January 1968. Technically, this model was a brand new development which had almost nothing in common with its predecessor. However, the same basic components had already been used in other Mercedes-Benz types: Front and rear wheel suspension was basically the same as that of the "dash-eight" models and the V8=engine was a familiar feature of the saloons, coupes and convertibles of the 280_SE_3.5 type.
With respect to the general concept the differences were less clear: Like its predecessor, the 350_SL was a two-seater with fully retractable roadster hood and removable hard top. However, the new models, represented a once and for all departure from the uncompromisingly hard sports car, - and, incidentally, even the pagoda-SLs, too, was not a true representation of that type - in fav0ur of a more comfortable yet powerful luxury two-seater.
The 350_SL_- with the internal code name R_107_- was equipped with numerous innovatory details, which were to result in increased passive and active safety and set the course for the future development of passenger cars. The fuel tank was no longer located in the rear of the car but had been transferred to a collision-proof position above the rear axle; In the passenger cabin, an upholstered dashpboard, flexible or retractable switches and buttons and the new four-spoked steering wheel with an in-built rebounding device and a broader uplholstered centre-piece provided a maximum of safety in case of collision.
New wind deflector profiles at the A=pillars, which served as drainage rails for dirt water in heavy rain and kept the windows clean even in poor weather conditions guaranteed very good vision. Further details, adding to the safety of the car, were clearly visible indicators as well as large taillights, which, thanks to their ribbed surface profile, were almost completely soil-repellent.
Half a year after the launch of the 350_SL a sister model was presented at the Paris Motoring Show; this was the 350_SLC type, a four-seated coupe with fixed roof, which technically and stylistically, closely resembled the roadster, but had a wheelbase, which was 360_mm wider.
In April 1973, both models, roadster as well as coupe, had also become available with a 4,5_litre V8 engine with increased cubic capacity. A low-compression 195_bhp version of this engine, which had been revised to comply with the US=legislation on emissions, had been available for exports since July 1971 and, with the North-American design of the 350_SLC, since July 1972.
In July 1974, the SL=Types programme was again extended: following the oil crisis in 1973, roadster and SLC=Coupe were now available with the 2,8_litre-dohc-injection engine, which had proven its worth for two years in the "dash-eight" product line and the S=class. This meant that the customer could now decide between three differently motorised SL=models which is nothing unusual today but was a complete novelty in the history of that class then. Only an experienced observer was able to distinguish these models from each other; whereas the 280_SL had narrow tyres, the 450_SL had an inconspicuous front spoiler, which was attached to the rear lower end of its front apron and served as an airing device for the radiator.
Between November 1975 and February 1976, all three engines were fitted with a new fuel injection system in order to comply with the stricter emission limits, which had been introduced in most European countries. The electronic "D=Jetronic" by bosch was replaced by a new mechanical "K=Jetronic", also by bosch. This step led in all three cases to a certain loss of power; in the 2,8_litre and 3,5_litre engines, compression had been slightly reduced. In order to facilitate maintenance, the two new V8=engines were fitted with a transistor ignition without contacts and hydraulic air gap compensation. In the 2,8_litre unit, compression was increased to its former value in 1978; with the help of some ancilliary measures the former driving performance was regained.
At the Geneva Motoring Show in March 1980, an uprated version of the roadster and coupe of product line 107 was presented; the equipment of the interior including the steering wheel had been brought up to the standard of the saloon cars of the S=class and the same happended with the technology. The former three-speed automatic converter was replaced by a 4=speed version. Moveover the light alloy engines of the S=class were built into many models of product line 107 in slightly modified form.
The new type 500_SL with its 5,0_litre V8 engine, which had been carried over from the 450_SLC_5.0 replaced the 450_SL. The 350_SL, too, was phased out after an production time of nine years; Their successor was the 380_SL which had a 3,8_litre light alloy unit that had been modelled on the five litre unit of the proven 3,5_ltr. V8 with gray cast iron block. Only the six cylinder engine of the 280_SLC remained in the programme in unchanged form. Regarding the exterior, there were only few differences compared to the predecessor models except for the type labels; all three SL=Types had a light alloy bonnet and were fitted with the inconspicuous front spoiler of the 450_SLC_5.0; Furthermore, the 500_SL was now fitted with a light alloy boot lid with black plastic tail spoiler, a feature that had been carried over from the five-litre coupe, too.
In autumn 1981 both V8=engines underwent profound revison in the context of the new "Daimler-Benz energy concept" in order to reduce fuel consumption and emissions. Apart from a higher compression, these measures included the insertion of a camshaft with changed control times, air-immersed injection valves and an electronic free wheel control. Following the adjustment of the camshaft, maximum torque was shifted to lower rev-counter values and in the case of the 3,8_litre engine, it was even increased. This unit had undergone dramatic changes: in order to achieve a better volume-to-surface ratio, boring had been reduced and cubic capacity had been augumented. The modified 3,8_litre=V8 engine now had a marginally increased cubic capacity. As compensation for these measures of economy, both eight cylinder engines had lost a little of their power. Rear axle transmission was adjusted in both cases to the new configuration of the engine.
These innovations however came too late for the SLC-coupes: Apart from the "Mercedes-Benz Engergy concept", the 380_SEC and 500_SEC types were presented at the International Automobile Fair in Frankfurt. they made the SLC-Models, which had been built for exactly ten years, effectively redundant.
It was clear, however, that time was not ripe yet for a replacement of the SL-Types, even after a production time of ten years. Four years after the presentation of the engergy concept, another comprehensive model revision package was applied, so that in september 1985, again at the Motoring Show in Frankfurt, a completely revised SL-Type programme was presented. Except for some minor face lifts, which affected primarily the front spoiler, the wheels and also resulted in an improved front wheel suspension, re-structuring of the engine range was the real point of the exercise.
A brand new 3,0_litre six cylinder engine, which nine months before had made its debut in the Intermediate class cars of product line W_124, replaced the well-tried 2,8_litre-dohc-engine, as had been the case with the S=class saloon. For the first time after 22_years there finally was a new sports car with the type name 300_SL. Another new engine was the 2_litre V8 engine, which had been created by boring open the 3,8_litre unit and which had replaced this engine in the SL, in the S=class saloon and in the SEC=coupe. The 5,0_litre engine had been modified, too; it was now fitted with electric ignition and the electro-mechanic injection system KE-Jetronic by Bosch, producing 245_bph.
The most spectacular innovation within the new range of engines was a 5,6_litre eight-cylinder engine, which had been developed from the 5,0_litre V8 by increasing its cubic capacity and now delivered 272_bhp. however, in this form, the new top engine was not used in the SL, but in the s=class saloons and coupes. The 560_SL was not available in Germany but was destined for export to the USA, Australia and japan; Emission legislation in these countries demanded the use of derated engines, which delivered only 230_SAE=bhp with a catalytic exhaust emission cleaning system. For many disappointed SL-fans in the "country of unlimited possibilities", the engine was still a revelation, as they had had to content themselves with the 157_SAE=bhp of the 380_SL model for years.
Production of the 300_SL_-_560_SL types ceased in august 1989, almost 18 years after serial production of the 350_SL had started; This meant that the SL=product line 107 had set a new record and it is highly unlikely, that this record will ever be broken: in the whole history of daimler-Benz there was no other product line, which continued over a similarly long time. In all, 237.287 cars were produced at Sindelfingen, a figure which clearly demonstrates the high popularity of product line 107.
These were succeeded by three SL=types of product line 129, which were unveiled to the public in March 1989. At that time, serial production had already been launched.
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