First Line’s in-house classic clutch engineer offers some advice to workshops that are faced with the challenge of replacing an ‘A’ or ‘AS’ type Borg & Beck clutch on a classic vehicle.
Although a lot of work on classic cars is undertaken by competent owners, many repair jobs are still outsourced to an independent workshop. When presented with a classic, technicians should respect the originality of the vehicle and fit brands that were used in the vehicle’s original manufacture. When it comes to the clutch, a large proportion of British-built classic cars were originally fitted with Borg & Beck, so for the replacement items, original Borg & Beck really is a viable option.
The ‘A’ type is usually of a single dry plate design, comprising a cover assembly, driven plate assembly and release bearing, which utilises a pressure plate that is driven by the pressed steel cover via machined pressure plate lugs engaging into slots.
The ‘AS’ design features a pressure plate driven by the pressed steel cover via a number of tangentially disposed spring steel straps. These deflect during clutch operation, without disturbing the concentric position of the pressure plate. One end of each pair of straps is riveted to the cover flange, while the other end is bolted to the pressure plate. This design eliminates friction between the cover and pressure plate.
In the original Borg & Beck clutch service manuals, it was advised that the technician carry out a full inspection of the clutch system as part of the vehicle’s maintenance schedule, as outlined below.
Removal of the clutch assembly from the vehicle
Loosen each of the bolts securing the clutch to the flywheel, but to avoid distorting the cover flange, slacken them a turn at a time, diagonally, until the pressure of the clutch springs is relieved. Next, remove the bolts and the complete clutch from the flywheel, with all parts except the driven plate remaining assembled to the cover.
Inspect the flywheel. Scoring may occur on the face of the flywheel, in which case it must be re-ground or replaced as even slight scoring will cause excessive wear of the clutch facings. The complete dismantling of the clutch was also advised in the original schedule. However, this is not advised today. It is more viable to replace the whole unit rather than dismantle the ‘A’ and ‘AS’ type assemblies to service the individual components, as this can be both time consuming and dangerous if a technician has not opened one up before, as it is fully loaded with springs.
When fitting the clutch back onto the vehicle, the principles employed in the past still resonate today – i.e. you should use a driven plate alignment shaft – as misalignment is responsible for almost every case of rapid spline wear, broken drive plates, damaged transmission bearings and gears.
As always, ensure the gearbox is adequately supported and not permitted to hang on the clutch, as serious damage may result. When guiding the gearbox into the assembly position, get the first motion shaft in true alignment with the driven plate hub and turn the main output shaft each way slightly – with gearbox in gear – to ensure smooth engagement of the splined parts.
A light smear of grease should be placed on the shaft prior to installation of the gearbox. Once installed, check the clutch pedal adjustment – in accordance with the vehicle manufacturer’s instructions. Borg & Beck’s 60+ product line portfolio provides the solution for more than 200 classic applications, including such icons as the Aston Martin DB4, Jaguar E Type, Morris Minor and Triumph TR range.