Several famous marques used A-type overdrives, including Jaguar, Aston Martin, Ferrari, Austin-Healey, Jensen, Bristol, AC and Armstrong Siddeley. The first unit to be created was the A-type overdrive, this was fitted to many sports cars during the 1950s. That is the history and I can confirm these units have been sold by their thousands and continue to work faultlessly in many applications (not just TR's) around the world, so now there is no need to go searching for components to build a device that may or may not work, it has all be designed for you and been field tested in thousands of cars for the last 30 years.The first production vehicle to feature the Laycock system was the 1948 Standard Vanguard Saloon. The 'N' and the 'P' in these part numbers indicates negative and positive earth variants. Two types of kits are available RTR1001K which is a basic unit suitable for both positive and negative earth and RTR1296NK, RTR1296PK which provide a facility to dim the indicator lamp independently for both day and night. And it is worth noting that both negative and positive earth devices are available. We recommend a light on the dash to identify the overdrive state. This applies to any gear change up or down the gearbox where the start point was an overdrive gear. If a fast change is required from say 2nd overdrive to non -overdrive 3rd, just move the gear lever to 3rd and the logic device will disengage overdrive for you as you pass through the gear shift gate. When a non-overdrive gear is required from an overdrive gear, flick the switch. When overdrive is required (in an overdrive enabled gear of course), flick the switch. The modus operandi is this: Whatever gear or state of overdrive the car is in when the ignition is turned off, the overdrive will be off when you turn on the ignition again. A flick switch is used to operate the system and in the case of TR4-6 the original switch can be modified to become a flick switch (Meaning momentary operation with self-return).
#Laycock overdrive j type full#
So how does it operate and how do you fit it? There is no need to remove the gearbox tunnel, the box of tricks and all the other fittings that come in the kit (which comes with full instructions), is wired into the existing wiring from the gearbox tunnel upwards to the switch and original relay (pre CF CR TR6 cars). I called this device a' Logic Overdrive device' (which has since become the generally accepted name for these devices)Initially the device was constructed of basic electrics but has since been redesigned and is now fully electronic. What is the background? Well, when Revington TR was called TR Spares Southwest in 1982 ish, I designed a device to allow me to change gear and overdrive at the same time specifically with racing in mind but obviously I found that the device was a fantastic improvement on all cars both road and competition.
#Laycock overdrive j type how to#
I have read with some amusement in magazines and on forums how owners of cars with electrically operated overdrives have wrestled with the concept of how to design and make such a device work, and I seemingly making it all sound desperately difficult. Logic overdrive devices: A note on the subject from Neil Revington Where the car is not fitted with an existing relay to operate the overdrive solenoid such as J type TR6 s, an additional relay must be fitted, full instructions for which are to be found in the kit. This device can be used on all electrically operated overdrives where inhibitor switches are employed on the gearbox to prevent the overdrive operating in certain low gears and reverse. We have a range of dash mounted momentary operation switches too which will suit TR2-3B and even TR4-6 should a dash mounted switch be acceptable. We can supply TR4-6 owners with a modified momentary column mounted switch RTR8207K, with the stalk extended to match the length of the original switch.
You can watch the You Tube video via the icon below. Watch out for the light on the dash inside the rim of the steering wheel coinciding with overdrive engagement.Ī momentary operation switch rather than the standard on/off switch operates the logic device.Revington TR have several solutions. Neil Revington reports that at his first outing to the Mdina GP in Malta, a fellow competitor questioned after practice if I had a sequential gearbox in my TR5! Our logic device can even impress onlookers. In this short video our customer Hamish explains how he uses this device HEREĮminent race and Rally driver, Jean Jacques Thuner was suitably impressed when he drove the works TR4 registered 6VC back in 1999. When changing gear with the overdrive left engaged, overdrive drops out automatically.įits all electrically operated overdrives and suits both positive and negative earth. Overdrive cannot be left in inadvertently, reducing strain on the overdrive. This clever device allows for fast and sequential overdrive operation.
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