RogerH Posted December 3, 2015 Report Share Posted December 3, 2015 Hi I started this on my engine rebuild thread but it is getting a bit confusing so I have re-started it here. The box was leaking like a sieve so along with the engine it came out of the car. Most of the leaking appears to be from the three selector shaft seals. The new O ring seals appear to be a loose fit probably work but I'm not happy) and do not fill the counterbore they sit in. I've tried a couple of lip seals - one, 13mm is also a bit loose *no worse than the O-ring), the other 12mm is a wee bit tight. More searching required. Or I could make my own. The other issue is the reverse light switch. I know where it goes. I now need to drill and tap a hole. On the other thread there was a lot of posting about the switch thread size - I know it is 5/8" diameter and is 13TPI (post on) This thread size is not standard (or so it would seem). There is only one known example in the universe (and I may need to scrounge it) M16 x 2mm is almost there but not quite - how perfect doe sit need to be. My thread gauge sits perfectly on the switch thread but rocks on the M16 tap. I have noted that the selector forks and shafts are not longer available new - Why????? The selector looks an easy enough casting to make more. The shafts are dead easy for any machine shop. The last point is the breather. The OD has a breather - so why is oil being forced out of the selectors!!! I shall introduce a new breather hole to the GB cover. Roger Quote Link to post Share on other sites
Rob Salisbury Posted December 3, 2015 Report Share Posted December 3, 2015 Hi Roger, The M16x2 thread works fine with the replacement reverse switch BAU1074A I got from Moss a couple of years ago, it needs careful shimming with fibre washers to work without leaving the shaft too stiff to move easily. Put the engineers hat away and go for it!! Cheers Rob Quote Link to post Share on other sites
RogerH Posted December 3, 2015 Author Report Share Posted December 3, 2015 Hi Rob, I'll do a test on a bit of gash material and see what happens. Roger Quote Link to post Share on other sites
Rob Salisbury Posted December 3, 2015 Report Share Posted December 3, 2015 Ah Ha, an experiment, a bit of Lab testing!!, I like it!! Quote Link to post Share on other sites
LGFromage Posted December 3, 2015 Report Share Posted December 3, 2015 Hi Roger, If you want O rings try these guys: http://www.barnwell.co.uk/pdf/Barnwell%20ORings.pdf as by checking the catalogue and for around £10 you can get a selection of sizes one of which may suit. Tim Quote Link to post Share on other sites
barkerwilliams Posted December 3, 2015 Report Share Posted December 3, 2015 And to link your threads ....... ........obviously used the wrong square ended spanner to remove the selector bolts. Alan Quote Link to post Share on other sites
RogerH Posted December 3, 2015 Author Report Share Posted December 3, 2015 I heard this whooshing sound - it was the previous post going straight over my head. Hi Alan, not sure what the point is. In fact I used an 8 point socket - but two of the little so and so's still broke, Roger Quote Link to post Share on other sites
AlanT Posted December 3, 2015 Report Share Posted December 3, 2015 (edited) You will want EPDM O-rings: http://www.chronos.ltd.uk/cgi-bin/sh000001.pl?WD=ring&PN=O_Rings.html#aESR_2e_2e_2e I've got 5/8in 14TPI Also 1/2in 13TPI for Helicoil. Edited December 3, 2015 by AlanT Quote Link to post Share on other sites
graeme Posted December 4, 2015 Report Share Posted December 4, 2015 I have noted that the selector forks and shafts are not longer available new - Why????? The selector looks an easy enough casting to make more. Roger Hi Roger, It may be a good idea for the 'Spares Development Fund' to get these made. Most gearboxes are going to need selector forks eventually. Cheers Graeme Quote Link to post Share on other sites
John L Posted December 4, 2015 Report Share Posted December 4, 2015 There is a breather in the top cover of the gearbox, its just a 1/16 hole, or may be even smaller, Its in the top cover, I think in the top left side, towards the front, but I may be wrong. If you clean the top cover I'm sure you will se it. John Quote Link to post Share on other sites
BlueTR3A-5EKT Posted December 4, 2015 Report Share Posted December 4, 2015 (edited) Roger, I have a tap to do the gearbox switch holes in the top cover somewhere if you get stuck. Peter W PS Sorry Roger, just looked and I have not found the tap. Peter W Edited December 4, 2015 by BlueTR3A-5EKT Quote Link to post Share on other sites
LGFromage Posted December 4, 2015 Report Share Posted December 4, 2015 You will want EPDM O-rings: http://www.chronos.ltd.uk/cgi-bin/sh000001.pl?WD=ring&PN=O_Rings.html#aESR_2e_2e_2e I've got 5/8in 14TPI Also 1/2in 13TPI for Helicoil. Not recommended for oils, kerosene etc. Tim Quote Link to post Share on other sites
RogerH Posted December 4, 2015 Author Report Share Posted December 4, 2015 Hi Folks, I have an M16x2mm tap and have been advised by previous explorers that it will work. I will do a test hole tomorrow. Roger Quote Link to post Share on other sites
Guest ntc Posted December 4, 2015 Report Share Posted December 4, 2015 Roger Good luck but rather than f it up take it to somebody that know s what they are doing. Quote Link to post Share on other sites
RogerH Posted December 4, 2015 Author Report Share Posted December 4, 2015 (edited) Hi Neil, wise words. I will still do an experiment. It is still baffling that this switch has a thread form that shouldn't exist. I appreciate that a tap does exist and I may have to take up the offer of borrowing it but how could ST possibly run a show with one non-standard tap. Roger Edited December 4, 2015 by RogerH Quote Link to post Share on other sites
stuart Posted December 5, 2015 Report Share Posted December 5, 2015 I think you will find its not just ST as the Jaguar Moss type gearbox and later all synchro boxes use the same switches. Stuart. Quote Link to post Share on other sites
RogerH Posted December 5, 2015 Author Report Share Posted December 5, 2015 Hi Stuart, quote so - where did this switch originate. Why design it with a thread form that doesn't exist (well, not common at least). It really is ahead scratcher. Roger Quote Link to post Share on other sites
AlanT Posted December 5, 2015 Report Share Posted December 5, 2015 Are you sure this isn't 5/8in 14 pipe-thread? This would be the obvious thing. Don't these switches have a bit of taper on them? Quote Link to post Share on other sites
RogerH Posted December 5, 2015 Author Report Share Posted December 5, 2015 Hi Alan, the O/D of the switch thread is 5/8". It is definitely 13TPI according to my thread gauge. M16 isn't quite there but should work - you can clearly see the difference between M16 and the switch. I do not think it is tapered. Roger Quote Link to post Share on other sites
mike3md Posted December 5, 2015 Report Share Posted December 5, 2015 Perhaps Joe Lucas is to blame for the odd size thread? I assume the switches all originally came from him? Quote Link to post Share on other sites
RogerH Posted December 8, 2015 Author Report Share Posted December 8, 2015 Hi Folks, had fun today. I started to do a trial assembly of the top cover. The reason for the rebuild was that it was leaking from the three O-rings. My first thoughts on the O-rings was to replace them with lip seals. This is not too easy as a 1/2" I/D seal needs to be significantly bigger than the seal counterbore that exists at present. The problem with the new O-rings is that they are a little slack on the shaft, similarly in the counterbore and also the counterbore is too deep. This allows the O-ring to floats back and forth, So I made my own O-rings using a slightly thicker gauge ring (from a kit) cutting the rubber to length and then supergluing it together. This now fits the counterbore better for diameter but is still too shallow. So I knocked up a 1mm shim washer to sit on top of the O-ring. See the pics. The seal plate holds everything in place. In the next few days I will drill/tap a hole for the reversing light switch. And then I can button it up Roger Quote Link to post Share on other sites
Revolution Posted December 8, 2015 Report Share Posted December 8, 2015 Hi Roger Looks a good job done! Notice in the first pic you have a tube of gel in the backgound.......is that for keeping your hair in place under your hat whilst you're at work??!!!! Cheers, Nick Quote Link to post Share on other sites
RogerH Posted December 8, 2015 Author Report Share Posted December 8, 2015 You cheeky monkey - that instant glue is required to stick rubber O rings to my fingers - it works to. Roger Quote Link to post Share on other sites
dingle Posted December 9, 2015 Report Share Posted December 9, 2015 I don't understand the quandary over the size of the isolator switch thread. The TR4 wsm calls it out as 16mmx2mm in the overdrive section. As far as why it is metric, my guess would be that Laycock(and a lot of other British manufactures) used an existing switch that had metric threads. Thanks for bringing up the o ring problem on the top cover. I have also found a large leak around the shift rods and agree that the available o rings don't fill the counterbore for the od and are a bit loose on the id. Berry Quote Link to post Share on other sites
RogerH Posted December 9, 2015 Author Report Share Posted December 9, 2015 Hi Berry, the WM may well state M16 but it isn't. It is nearly M16 but not quite. It is 5/8 x 13TPI - this is not M16. I simply can't understand why anybody would make a mass produced item using a non-standard thread form - it is not engineering, it is not sense. An M16 tap will not go down a inhibit switch threaded hole that TRiumph made in the 60's - it is not M16. Roger Quote Link to post Share on other sites
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