Retro Fit Overdrive System
With 45 years experience of maintaining Rolls-Royce and Bentley Motor Cars we first introduced an overdrive system for pre-war cars in the late 1980's.
Now, for all those considering a 'fifth gear' we have further refined the overdrive system which received such high acclaim from Lt. Col. Eric Barras, President of the Rolls-Royce Enthusiast Club, when it was first introduced.
Utilising the tried and tested Laycock Unit, suspended and self aligning from three flexible mounts on a substantial cross-member, the complete package including balanced prop-shafts, adapters, wiring loom, speedometer drive etc,. has been revised to appeal to the self-fit customer. Easily fitted and replacing the existing prop-shaft, there is no need for drilling, welding or the re-routing of One-shot pipes or the existing wiring harness. In addition the complete installation can be removed at any time, leaving absolutely no trace. Each Laycock Unit is produced to order with a matched speedometer drive ratio. The Overdrive is operated by the flick of a switch (supplied) whilst engagement is restricted, for design reasons, to top gear. A full 'Factory Fitting Service' is available and 'On Site' fitting can be arranged.
This overdrive system is suitable for all ladder frame chassis vehicles originally fitted with a prop-shaft. We are certain that it will be of interest to the true enthusiast, not least because the simplicity of the design provides a considerable financial saving when compared with similar systems.
Technical Information
The engagement of the Overdrive gear is hydro-electrical. An integral plunger pump, driven by the input shaft, provides the regulated hydraulic pressure, which is controlled by an electric solenoid valve, switch operated from the dashboard.
Because the efficiency of the plunger pump is directly proportional to the RPM of the gearbox output shaft, it is important that engagement of the overdrive is limited to top gear and an inhibitor switch is provided for this purpose.
The Overdrive is slung under a substantial cross member, which is bonded and clamped to the chassis. Three rubber mounts (silent blocks) are used, in a ‘tripod configuration’, configured to limit oscillation/vibration, to insulate the Overdrive and eliminate noise. The unit is self-aligning when fitted and the need to drill or weld the vehicle chassis is eliminated making self installation simple. However, a fitting and testing facility is available at our factory.
On The Road
For a given road speed, the Overdrive will reduce the engine revs by 22%:
Direct drive: 50mph, 2,500rpm
Overdrive engaged: 50mph, 1,960rpm
Conversely, and of interest to Motorway users and those considering touring, for a given engine speed the Overdrive will provide an additional 28% of road speed:
Direct drive: 50mph, 2500rpm
Overdrive engaged: 64mph, 2500rpm
Servicing
The use of standard approved gearbox oil is recommended for use in the Overdrive and that the oil should be drained and replenished at the same time as the gearbox oil.
To Order
Kindly measure your vehicle and enter the dimensions/information as appropriate.
Because each Overdrive Package is tailored to individual specifications, please enclose a deposit of £500.00 with your order. Factory lead time are usually two to three weeks.
Overdrive Package
Intermediate Shaft:
Suitable Gearbox Flange Adaptor
Shaft with Universal Joint & Connecting Flange
Overdrive Unit:
‘Laycock’ Late Type Retro-fit Overdrive Complete
Cross Member
‘Silent’ Mounting Blocks
Support Brackets & Clamps Etc
Chassis Clamp Adhesive
Rear Propshaft:
Suitable Diff Pinion Adaptor Flange
Standard Splined Sliding Joint, Universal Joint & Shaft
Speedometer Drive:
Gear Box Blanking Cover
Cable Adaptor Complete
Speedometer Extension Cable Complete
Electrical:
Manual Switch with Escutcheon
Inhibitor Switch and Bracket
Fuse Box
Relay
Complete Wiring Harness with Support Clips
Literature:
Fitting Instructions
Wiring Diagram
12 Months Warranty
:: Click here to download the brochure & price lists
For more information please contact us.