silverfox4 Posted March 8, 2018 Report Share Posted March 8, 2018 My 4A has A-Type OD but only has the two inhibitor switches and no reverse switch. I'm trying to understand how the OD could ever be engaged in reverse. With reverse engaged, both switches for 1st/2nd and 3rd/4th would be in the neutral position so the solenoid could not be activated. If running in 2nd OD and shifting across the gate, the OD drops out momentarily but will re-engage on selecting 3rd and same for 3rd to 4th as long as the column switch is "on" - this I follow. It's the logic "engaging OD in reverse issue" that I'm having trouble with. Cheers, Alf Quote Link to post Share on other sites
graeme Posted March 8, 2018 Report Share Posted March 8, 2018 Hi Alf, You can't engage OD in reverse unless the wiring is incorrect. What can happen is the the OD clutch can stick in OD and, even though you have switched OD off, it will allow you to select reverse while stuck in OD. This will destroy the OD I understand. Hope this clarifies it for you. Cheers Graeme Quote Link to post Share on other sites
lightningburns Posted March 8, 2018 Report Share Posted March 8, 2018 Hi Alf, If you think of the two switches not as inhibitor switches but as enabler switches i.e. if either one is operated then the circuit is made for the overdrive to operate. The switch (if you had one ) for reverse is used only for the reversing lights. As Graeme says the issues highlighted by him can cause the overdrive to operate. When I bought my TR there was a large sticker on the dash instructing the driver to make sure the overdrive switch was not operated when reverse was selected. Sure enough the overdrive solenoid would click in if you selected reverse ! It was a wiring issue, a prev owner had put an eth feed direct to the overdrive switch to enable the overdrive to work, the actual fault was one of the enabler switches not working. Regards, John Quote Link to post Share on other sites
RogerH Posted March 8, 2018 Report Share Posted March 8, 2018 Hi Alf, as per Graham/John's reples - but there are other mechanical problems that will hold OD in. I bought a replacement OD solenoid and the rubber boot on the plunger was so stiff and tight on the plunger that it would hold it up in the engaged position with the OD switch in the off position. Last summer I replaced the oD operating cam shaft 'O' rings. These were a fraction too tight and held the operating cam in position. Roger Quote Link to post Share on other sites
mjdearing Posted March 8, 2018 Report Share Posted March 8, 2018 +1 Roger, yep get the correct O rings from Sheffield OD services I made this same mistake and it took some solving. Martin Quote Link to post Share on other sites
Rob Salisbury Posted March 8, 2018 Report Share Posted March 8, 2018 Hi Alf, If you have a look at the wiring diagram for the overdrive you will see that the inhibitor switches are in the earth return path, so if there is a wiring fault at the column switch and it can switch directly to earth, bypassing the inhibitor switches, then you can get the overdrive solenoid energised in any gear (overdrive first is interesting!!), and if you forget to switch to off then you can get overdrive in reverse, not for very long, 'cause there is a loud bang and the unidirectional clutch disintegrates......... ask me how I know this!!!! Cheers Rob Quote Link to post Share on other sites
Steve Priest Posted March 8, 2018 Report Share Posted March 8, 2018 (edited) Hi Alf, If you have a look at the wiring diagram for the overdrive you will see that the inhibitor switches are in the earth return path, so if there is a wiring fault at the column switch and it can switch directly to earth, bypassing the inhibitor switches, then you can get the overdrive solenoid energised in any gear (overdrive first is interesting!!), and if you forget to switch to off then you can get overdrive in reverse, not for very long, 'cause there is a loud bang and the unidirectional clutch disintegrates......... ask me how I know this!!!! Cheers Rob Ah yes, Rob - I had this exact problem with a new O/D switch. I tested it with a DVM and found that one of the terminals was making connect with the switch casing. On closer inspection this was because the small fibre disk that insulates the spring/ball bearing from the contact plate was missing. I took the switch apart and found the disk stuck to the grease inside the switch! Steve Edited March 8, 2018 by Steve Priest Quote Link to post Share on other sites
Fireman049 Posted March 8, 2018 Report Share Posted March 8, 2018 Hi Alf ~ Here's the wiring diagram for the overdrive. Tom. Quote Link to post Share on other sites
Tom Fremont Posted March 8, 2018 Report Share Posted March 8, 2018 I didn't see it above, so another reason is improper adjustment as indicated by the lever across from the solenoid. I've played around with slight adjustments of these to effect rapid engagement and delayed disengagement ( allows gearshifts up without actually leaving O/D ) only to have them stay engaged. However, the moment I tried to back out of the garage to test the settings the engine would start to bog - and I knew better than to insist! So a light touch works well here. The one way clutch ensures the output shaft turns at the same rpm or faster than the input shaft, CW facing the car. This prevents the engine racing up when shifting under load prior to engaging. When the O/D is engaged the outer race of the clutch is locked to the housing, so forcing the rollers up the ramps in reverse breaks it up. Cheers, Tom Quote Link to post Share on other sites
silverfox4 Posted March 9, 2018 Author Report Share Posted March 9, 2018 Thanks All, So I was right then and the feared "engaged in reverse" situation is largely the result of a malfunction somewhere along the line from internal OD issues to phantom wiring, faulty switches, and maybe ambitious settings (Tom?) Here I am getting ready to install a reverse switch to conceive dastardly plan to make sure the OD cannot be engaged in reverse when there are more obtuse or peripheral things to worry about. I do have mine apart and it is in a very sorry state, but more on that later............ Again thanks for the valued input Quote Link to post Share on other sites
RogerH Posted March 9, 2018 Report Share Posted March 9, 2018 Hi Alf, do install the reverse switch but not for the OD - it really doesn't need it - but for reversing lights if ever, in the future, you decide to fit them. The Inhibit switches really do a very good job. If you do go for reversing lights try and be a little inventive. here are mine Roger Quote Link to post Share on other sites
Fireman049 Posted March 9, 2018 Report Share Posted March 9, 2018 Hi Roger ~ I think your reversing lights are really neat. Tom. Quote Link to post Share on other sites
pfenlon Posted March 9, 2018 Report Share Posted March 9, 2018 Hi Alf, do install the reverse switch but not for the OD - it really doesn't need it - but for reversing lights if ever, in the future, you decide to fit them. The Inhibit switches really do a very good job. If you do go for reversing lights try and be a little inventive. here are mine Roger P1030748a.jpg Oh that really is too Posh, signed Billy Envy. Quote Link to post Share on other sites
Lebro Posted March 9, 2018 Report Share Posted March 9, 2018 He's just showing off Quote Link to post Share on other sites
RogerH Posted March 9, 2018 Report Share Posted March 9, 2018 Yes. Quote Link to post Share on other sites
silverfox4 Posted March 9, 2018 Author Report Share Posted March 9, 2018 Hi Roger, I have just ordered the 16 mm x 2 mm tap and switch, so might as well have a go. Now those (presume 2) are some pretty fancy reversing lights! I notice you have orange signal lens. Was that UK spec - mine are red Cheers, Alf Quote Link to post Share on other sites
RogerH Posted March 9, 2018 Report Share Posted March 9, 2018 Hi Alf, UK flashers are orange. Roger Quote Link to post Share on other sites
silverfox4 Posted March 9, 2018 Author Report Share Posted March 9, 2018 hhmm, may consider changing mine in the future Alf Quote Link to post Share on other sites
stuart Posted March 10, 2018 Report Share Posted March 10, 2018 Hi Roger, I have just ordered the 16 mm x 2 mm tap and switch, so might as well have a go. Now those (presume 2) are some pretty fancy reversing lights! I notice you have orange signal lens. Was that UK spec - mine are red Cheers, Alf Except its not that size, we have had this discussion many times on here and although the metric on will work its not what Triumph used originally. Stuart. Quote Link to post Share on other sites
RogerH Posted March 10, 2018 Report Share Posted March 10, 2018 Except its not that size, we have had this discussion many times on here and although the metric on will work its not what Triumph used originally. Stuart. +1 The thread size is 5/8 x 13 TPI There is no thread size like this. The Holtz is close at 13.1 tpi but doesn't get the cigar What made ST go off in this direction - was it the French perhaps or maybe Brexit. A Stuart says the 16mm x2 will work Roger Quote Link to post Share on other sites
Rob Salisbury Posted March 10, 2018 Report Share Posted March 10, 2018 Did Triumph make the switch, or did they use a switch that was available (from Lucas presumably)? +another 1 for an M16x2 working, even though it's wrong. Cheers Rob Quote Link to post Share on other sites
RogerH Posted March 10, 2018 Report Share Posted March 10, 2018 Hi Rob, I don't know why but I have this feeling of a French connection somewhere. Did ST align with the French pre-war. Roger Quote Link to post Share on other sites
Rob Salisbury Posted March 10, 2018 Report Share Posted March 10, 2018 Hi Roger, Had a quick look through Wikiwhatsit and can't find any French connection, early on a connection to Germany, ........ no, I think it's a chicken or egg question, which came first, the hole with a screw thread, or a switch with a screw thread!!, maybe the thread has some electrical connections somewhere in it's past? Cheers Rob Quote Link to post Share on other sites
silverfox4 Posted March 10, 2018 Author Report Share Posted March 10, 2018 Now that's interesting, though the consensus is that the M16x2 is OK to use .(out of curiosity I must check for the 5/8-13). My take away on the reverse engagement issue is to now look into a dash light indication for solenoid engaged.. Cheers, Alf Quote Link to post Share on other sites
RogerH Posted March 10, 2018 Report Share Posted March 10, 2018 Hi Alf, you can get a 5/8 x 13tpi tap made but it does not exist as a standard thread form (anywhere in the known or unknown Universe). The 16mm x 2mm fits OK. Roger Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.