michael pridham Posted May 19, 2020 Report Share Posted May 19, 2020 Hi Folks. I have a 74 Tr6 with a J type overdrive which works on 2nd gear as well as 3rd+4th would anybody be able to tell me why this is so, I thought it was only the A type which worked on 2nd gear. Thanks Michael Quote Link to post Share on other sites
Paul Hill Posted May 19, 2020 Report Share Posted May 19, 2020 You might have a A type and you don’t know it. Really I ain’t got a clue, but like you I thought only J type worked in 3 & 4 Quote Link to post Share on other sites
peejay4A Posted May 19, 2020 Report Share Posted May 19, 2020 Somebody has wired the inhibit switches to operate like an A type. As I have done on my 4A. Quote Link to post Share on other sites
Nigel A Posted May 19, 2020 Report Share Posted May 19, 2020 I have a J type, but had an extra hole drilled into the top cover to take another inhibit switch. this gives me overdrive in second which only gets used in traffic jams and driving in central London Nigel Quote Link to post Share on other sites
Mike C Posted May 19, 2020 Report Share Posted May 19, 2020 Just make sure the O/D doesn't engage in first or reverse. When I originally got my car it's O/D solenoid was wired with a feed directly from the battery - bypassing the inhibit switches. Quote Link to post Share on other sites
astontr6 Posted May 20, 2020 Report Share Posted May 20, 2020 22 hours ago, michael pridham said: Hi Folks. I have a 74 Tr6 with a J type overdrive which works on 2nd gear as well as 3rd+4th would anybody be able to tell me why this is so, I thought it was only the A type which worked on 2nd gear. Thanks Michael I have a 1973 TR6 with a J Type Over Drive and it has 2nd gear operation in overdrive. When my engine was rebuilt the gearbox plus O/D where sent to ORS for overhaul. I asked about J type units can they be converted to operate on 2nd? They said it is easy to do on yours as it was a very early 73 model as BL were still using up their old gear box extensions. All they had to do was to undo the blanking plug and screw in another switch! Otherwise a bit of drilling and tapping is required on the later ones? Bruce. Quote Link to post Share on other sites
DRD Posted May 20, 2020 Report Share Posted May 20, 2020 Mine does as well, I can only assume that it was done by a PO when the gearbox was rebuilt. Quote Link to post Share on other sites
super6al Posted May 20, 2020 Report Share Posted May 20, 2020 +1 Quote Link to post Share on other sites
Austin Branson Posted May 23, 2020 Report Share Posted May 23, 2020 I converted mine to operate in 2nd gear as well. I had a blanking plug, which I simply unscrewed, and screwed in a micro-switch. It’s a 1974 CF. It seems fine. I did this more than 10 years ago, though I am aware that the ability to handle high power in the J is suspect. Regards, Austin Quote Link to post Share on other sites
c.hydes Posted May 23, 2020 Report Share Posted May 23, 2020 My J-Type overdrive has a 2nd gear switch fitted, but not wired into the circuit, which is correct for my car. So what are the benefits of having 2nd gear overdrive enabled, and what are the "pitfalls" or dangers, like some practical experience from users here before wiring it to the circuit? Colin. Quote Link to post Share on other sites
Nigel A Posted May 23, 2020 Report Share Posted May 23, 2020 I only ever use o/d 2nd in very slow moving traffic and find it makes for relaxed driving. Quote Link to post Share on other sites
c.hydes Posted May 23, 2020 Report Share Posted May 23, 2020 So I assume it engages/disengages smoothly at low revs and no sudden "jecks" etc? C/ Quote Link to post Share on other sites
Nigel A Posted May 23, 2020 Report Share Posted May 23, 2020 You can feel it but no real jerk Nigel Quote Link to post Share on other sites
ntc Posted May 23, 2020 Report Share Posted May 23, 2020 1 hour ago, c.hydes said: My J-Type overdrive has a 2nd gear switch fitted, but not wired into the circuit, which is correct for my car. So what are the benefits of having 2nd gear overdrive enabled, and what are the "pitfalls" or dangers, like some practical experience from users here before wiring it to the circuit? Colin. Not wishing to upset some but not a good idea it will slip if pushed hard, that's why Triumph and others did not do it. Quote Link to post Share on other sites
Austin Branson Posted May 23, 2020 Report Share Posted May 23, 2020 1 hour ago, c.hydes said: My J-Type overdrive has a 2nd gear switch fitted, but not wired into the circuit, which is correct for my car. So what are the benefits of having 2nd gear overdrive enabled, and what are the "pitfalls" or dangers, like some practical experience from users here before wiring it to the circuit? Colin. There aren’t really any pitfalls. It’s a very useful gear, as the TR gearbox has quite a gap between 2nd and 3rd. If you engage/disengage at a steady, light throttle, it’s pretty smooth. Quote Link to post Share on other sites
astontr6 Posted May 24, 2020 Report Share Posted May 24, 2020 16 hours ago, ntc said: Not wishing to upset some but not a good idea it will slip if pushed hard, that's why Triumph and others did not do it. The J type was designed to slip on engagement as the Volvo boys did not like the wham bam engagement of the A type. Also Volvo were GKN's biggest customer for O/D, so they called the tune! The J type was also less likely to cause warranty claims on the driveline. Bruce. Quote Link to post Share on other sites
ntc Posted May 24, 2020 Report Share Posted May 24, 2020 2 hours ago, astontr6 said: The J type was designed to slip on engagement as the Volvo boys did not like the wham bam engagement of the A type. Also Volvo were GKN's biggest customer for O/D, so they called the tune! The J type was also less likely to cause warranty claims on the driveline. Bruce. Bruce The change to J type was based on cost, as you point out Volvo wanted a cheaper alternate and smaller in size. Quote Link to post Share on other sites
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