Clarky Posted January 18, 2022 Report Share Posted January 18, 2022 Hello I am rewiring my 1973 TR6 which has a J type overdrive and was just wondering if it is necessary to have a relay in the circuit, there seems to bee contrasting views on this subject? If it is a requirement could anyone supply/point me in the direction of a wiring diagram for the relay. I have a basic idea but would like to confirm these details. Kind Regards Andrew Quote Link to post Share on other sites
RobH Posted January 18, 2022 Report Share Posted January 18, 2022 (edited) No need for a relay Andrew. The J type solenoid draws only around 2 Amps which is well within the capability of a normal switch. Are you intending to have a 'logic unit' ? Many users consider it worthwhile; as the name suggests it makes the operation rather more logical. There have been several alternative circuits posted in previous threads. Edited January 18, 2022 by RobH Quote Link to post Share on other sites
Clarky Posted January 18, 2022 Author Report Share Posted January 18, 2022 Hello and many thanks I've not really thought about a logic unit, can you point me in the direction of any information relating to this so I can understand its operation. All the best Andrew Quote Link to post Share on other sites
RobH Posted January 18, 2022 Report Share Posted January 18, 2022 Normally when you switch the overdrive on, it stays on even if you change gear (between 3rd and 4th on a J type). With it on you find yourself going from 2nd to 3rd OD to 4th OD changing up and from 4th OD to 3rd OD to 2nd when changing down. With a logic unit the overdrive is disconnected at each shift, so you go from 2nd to 3rd to 3rd OD to 4th to 4th OD - like having a closer ratio gearbox. On the down change you go from 4 OD to 3rd so you get greater acceleration. If you want overdrive you have to switch it on again after each gear change. Instead of the standard on-off overdrive switch you can use a 'momentary' one - a flick switch - some people fit a push-button on the gear knob. There are some (rather expensive) ready-made units available like the one from Revington, or if you are happy dabbling with electrics you can make your own using a few readily available bits at a fraction of the price. Here are a couple of earlier threads: https://www.tr-register.co.uk/forums/index.php?/topic/76663-over-drive-logic-revisited/ https://www.tr-register.co.uk/forums/index.php?/topic/78482-home-brew-overdrive-logic-controller/&tab=comments#comment-740865 Quote Link to post Share on other sites
Clarky Posted January 18, 2022 Author Report Share Posted January 18, 2022 Hello Lot’s to focus on here, sounds like it’s worth tackling myself. Many thanks for your time. Andrew Quote Link to post Share on other sites
ianc Posted January 19, 2022 Report Share Posted January 19, 2022 See my article in TR Action 203 (May 2005) for a description of Revington's offering. Members of the Register can view all copies of TR Action (and Newsletters) by logging in to the Register's website. Ian Cornish Quote Link to post Share on other sites
Clarky Posted January 19, 2022 Author Report Share Posted January 19, 2022 Ian Thanks I will take a look. Kind Regards Andrew Quote Link to post Share on other sites
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