page_title: Lotus Elan
section_title: Drive train
hierarchical_section_title: Lotus Elan / Lotus Elan 1500, 1600, S2, S3, S4, Sprint / Construction / Drive train
caption_attribution_description: English: Rotoflex drive coupling. Typical use: Automotive driveline (e.g. Ford GT40, Lotus Elan, Triumph GT6)
context_page_description: Lotus Elan is the name of two separate ranges of automobiles produced by Lotus Cars. The first series of cars was produced between 1962 and 1975 as a rear-wheel drive vehicle. The second series was produced between 1989 and 1995 as a front-wheel drive vehicle.
context_section_description: The engine, gearbox and differential were all sourced from Ford UK components. See below for details on the engine. The gearbox was a high volume unit used widely across the Ford range (Anglia, Cortina, etc.). Lotus offered regular and close ratio versions. The differential unit was also sourced from Ford but converted for independent rear suspension use (contemporary Ford cars used live rear axles). Three differential ratios were offered at various times during the production life of the vehicle: 3.55, 3.77 and 3.9. Most Elans were fitted with 3.77 differentials. 3.90 differentials, which provided the best acceleration, were often favored by purchasers of early cars, while 3.55 differentials became more common in later cars (especially the more powerful Sprints) to provide more relaxed cruising on newly built highways.
  The final drive used four Rotoflex couplings to connect the differential output shafts to the rear hubs. These "rubber doughnut" couplings were widely used at the time for road vehicles (e.g. Hillman Imp, Triumph GT6) and racing (e.g. Ford GT40, Lotus 21), prior to the availability of constant velocity (CV) joints. In the case of the Elan, which had exceptionally supple rear suspension that allowed significant vertical wheel travel, the deformation of the Rotoflexes in operation resulted in some "wind up" of the couplings. This could be readily detected by the driver, especially at takeoff and during gear changes, and was slightly disconcerting when driving an Elan for the first time. In practice drivers typically adjusted their clutch technique within a few minutes and no longer noticed it. In recent years the uncertain quality of replacement Rotoflex couplings, combined with the availability of half-shafts built with CV joints, has resulted in many Elans being converted from Rotoflex to CV joint drive.
  A notable feature of the drive train design was its use of standard, mass-produced components in combination with a minimal number of specialized aluminium castings to create a power unit and transmission suitable for a high performance sports car:
  The engine head and timing chest. Converted the Ford Kent pushrod engine into a twin overhead cam engine.
  The differential rear cover & carrier. Converted a live axle to independent suspension operation.
  The rear wheel hubs. Required for the Chapman Strut rear suspension.
  These three items were unique to the Elan (although the engine was subsequently used widely in other vehicles).
caption: Rotoflex drive coupling
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