qim Posted March 22, 2017 Report Share Posted March 22, 2017 Any ideas about where I should start looking? Thanks Quote Link to post Share on other sites
Lebro Posted March 22, 2017 Report Share Posted March 22, 2017 Top of gearbox - isolating switches - wiring & adjustment. Bob. Quote Link to post Share on other sites
qim Posted March 22, 2017 Author Report Share Posted March 22, 2017 Top of gearbox - isolating switches - wiring & adjustment. Bob. I'll get the electrician to have a look at it. What sort of adjustment can you do there? On 3rd and 4th I usually get a jerk when I engage overdrive Quote Link to post Share on other sites
RogerH Posted March 22, 2017 Report Share Posted March 22, 2017 Hi Qim, have got a good wiring diagram http://www.advanceautowire.com/tr24a.pdf Start at the beginning. With the GB in 4th gear and ignition ON, does the dashboard switch make the relay click. If YES, does the relay supply 12V to the solenoid If NO, are the inhibit switches functioning one or the other should be shorted out. If you are getting 12V to the solenoid is the GB earthed. Apply a separate 12V and earth to the solenoid. Roger Quote Link to post Share on other sites
RogerH Posted March 22, 2017 Report Share Posted March 22, 2017 I'll get the electrician to have a look at it. What sort of adjustment can you do there? On 3rd and 4th I usually get a jerk when I engage overdrive Hi Qim, you do not really want the OD/GB to jerk when engaging OD this can cause things to break. Try to match the engine revs for a smooth engagement. Comin gout of OD is important to do it smoothly. Roger Quote Link to post Share on other sites
qim Posted March 22, 2017 Author Report Share Posted March 22, 2017 (edited) Try to match the engine revs for a smooth engagement. Hi Roger What do you mean by that? Controlling revs before engaging O/D, or adjusting the "valve" on top of the gearbox Thank you for the wiring diagram. In fact, I have been looking for a thread that included a picture of the top of the gearbox marking where 2nd, 3rd, and 4th valves were positioned, but can't find it! Help... Edited March 22, 2017 by qim Quote Link to post Share on other sites
Rod1883 Posted March 22, 2017 Report Share Posted March 22, 2017 (edited) Qim - you may not have a switch for second gear o/d? Found this picture on line, may help - link Edited March 22, 2017 by Rod1883 Quote Link to post Share on other sites
qim Posted March 22, 2017 Author Report Share Posted March 22, 2017 (edited) Qim - you may not have a switch for second gear o/d? Found this picture on line, may help - link 000_3497-500x375.jpg Hi Rod I do! I have THREE of those valves; I saw them. Ok I found the picture (Roger's), which is attached. I also found another diagram to go along with Roger's. Will it confuse the electrician? is it for a 3A? Edited March 22, 2017 by qim Quote Link to post Share on other sites
Rod1883 Posted March 22, 2017 Report Share Posted March 22, 2017 I was going to say that one of those switches is for the reversing light, then saw you had added a picture. As Lebro above says, it is probably the switch that is faulty, or a poor/faulty connection to it, or its adjustment that is preventing the ball inside dropping to make contact. Quote Link to post Share on other sites
peejay4A Posted March 22, 2017 Report Share Posted March 22, 2017 (edited) As Roger's picture shows, the third switch is for a reversing light. Edit: as above^^^ Edited March 22, 2017 by peejay4A Quote Link to post Share on other sites
qim Posted March 22, 2017 Author Report Share Posted March 22, 2017 It looks like that the reason the 2nd is not working is becuase there is no wire coming out of the valve for the 2nd gear.... Although I am sure that my electrician can work out the diagrams, could you tell me basically what he has to do? 1- put a wire to the 2nd gear valve 2- ??? 3- ??? where does the wire go from the 2nd gear valve? Thanks Quote Link to post Share on other sites
peejay4A Posted March 22, 2017 Report Share Posted March 22, 2017 Both the inhibit switches are connected in parallel as Roger's diagram shows. Quote Link to post Share on other sites
TR 2100 Posted March 22, 2017 Report Share Posted March 22, 2017 Top of gearbox - isolating switches - wiring & adjustment. Bob. qim - Really cannot see it being anything else. The isolator switches in the gearbox top cover are no more than switches to earth. Thus, the overdrive cannot engage unless 2nd, 3rd or 4th gears are selected. Selecting overdrive in 1st puts too much torque through the gearbox. Selecting overdrive in reverse will k-nacker the gearbox Adjustment of the switches is height only - adjusted by removal of fibre waskers under the isolator switch. As it's hassle removing the tyrim and gearbox cover, you can check if it's the 2nd gear isolator switch by taking the earth from the overdrive switch directly to earth. It should now operate in ALL gears - thus you can check that it will operate in 2nd - but make very very sure you don't drive it like that. It's easy to forget overdrive is engaged and select reverse! Expensive problem. AlanR Quote Link to post Share on other sites
qim Posted March 22, 2017 Author Report Share Posted March 22, 2017 It's easy to forget overdrive is engaged and select reverse! So, why in the picture that I posted (provided by Roger) is there a connection to reverse?!!! Quote Link to post Share on other sites
Rod1883 Posted March 22, 2017 Report Share Posted March 22, 2017 So, why in the picture that I posted (provided by Roger) is there a connection to reverse?!!! There isn't, it's a separately wired switch for the reversing light, not overdrive Quote Link to post Share on other sites
Guest Posted March 22, 2017 Report Share Posted March 22, 2017 So, why in the picture that I posted (provided by Roger) is there a connection to reverse?!!! reverse light switch. Common on certain saloons and later TRs Quote Link to post Share on other sites
RogerH Posted March 22, 2017 Report Share Posted March 22, 2017 Hi Qim, this is important - the switch marked reverse is to power the reversing lights upon gear selection. It has nothing to do with OverDrive in reverse gear. Two switches allow OD - in 2nd (one switch) & 3rd/4th (another switch does both) The switches are simply in parallel - either switch will allow overdrive to energise. As for matching the engine revs. When travelling at 60KPH in 4th OD - the engine revs will be 2500 for example. If you disengage OD the road wheels will try to increase the engine revs (because it should be 3000 without OD (example) and that causes a sudden bang in the OD - NOT good. So, when disengaging OD increase the engine revs with the throttle so that the engine, if anything, will be revving slightly higher than the road speed requires. It is worse disengaging OD than engaging OD but higher revs is always better. You could also depress the clutch as if changing gear. Roger Quote Link to post Share on other sites
Rod1883 Posted March 22, 2017 Report Share Posted March 22, 2017 ...another comment I would make is that I have not connected the switch for second gear on my car (TR2) - I see little point in overdrive on second gear to be honest. Quote Link to post Share on other sites
mike3md Posted March 22, 2017 Report Share Posted March 22, 2017 Hi Qim, I notice that you refer to the switches on the top of the 'box as valves - they are NOT valves, but simple plunger type switches, which operate on the selector rods to allow the o/d to work - as per Roger's description. Mike Quote Link to post Share on other sites
qim Posted March 22, 2017 Author Report Share Posted March 22, 2017 (edited) So, when disengaging OD increase the engine revs with the throttle so that the engine, if anything, will be revving slightly higher than the road speed requires. Hi Roger Well, that's a problem, as I tend to disengage the OD to help me brake... and been doing that for 40 years... Edited March 22, 2017 by qim Quote Link to post Share on other sites
peejay4A Posted March 22, 2017 Report Share Posted March 22, 2017 You will learn how to allow the overdrive to engage and disengage relatively smoothly by adjusting the throttle as you operate the overdrive switch. I wouldn't worry about it. Personally I pay more attention to pointing the car in the right direction than agonising over how smoothly the overdrive is going to work. I've had A type and J type and they have their differences but they're both difficult to break under normal driving conditions. Just drive it. Quote Link to post Share on other sites
qim Posted March 22, 2017 Author Report Share Posted March 22, 2017 I think that before messing with the OD I should have ready whatever I need to adjust the switches. What is it that you need? from an earlier post it is about the height, so do I need some spacers, washers, whatever? Quote Link to post Share on other sites
TR 2100 Posted March 22, 2017 Report Share Posted March 22, 2017 Hi Roger Well, that's a problem, as I tend to disengage the OD to help me brake... and been doing that for 40 years... Well, it's your car so you are free to use it NOT as intended ! AlanR Quote Link to post Share on other sites
TR 2100 Posted March 22, 2017 Report Share Posted March 22, 2017 I think that before messing with the OD I should have ready whatever I need to adjust the switches. What is it that you need? from an earlier post it is about the height, so do I need some spacers, washers, whatever? If anything, you will need to remove/reduce spacers, so nothing extra required. AlanR Quote Link to post Share on other sites
Guest Posted March 22, 2017 Report Share Posted March 22, 2017 Hi Roger Well, that's a problem, as I tend to disengage the OD to help me brake... and been doing that for 40 years... I would NOT recommand this procedure with a TR's overdrive... last time I looked brake pads were a lot cheaper than an OD rebuild... Quote Link to post Share on other sites
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