Wendy Dawes Posted August 25, 2022 Share Posted August 25, 2022 Hi All , I’m planning to fit a J type overdrive gearbox from spitfire Mk1V to my 12/50 Herald, in the near future. it currently has the standard 3 rail 3 synchro box and the original 1147 engine. The D type gearboxes are so difficult to find now but I believe it’s possible to fit a J type as I know a couple of people who have them in their Herald, although they are the 13/60 model. I have upgraded the clutch to the 13/60 diaphragm type and it has the 13/60 flywheel. what alterations and fabrications will this entail as it’s a new venture and something I have never had the opportunity to watch being done. thank you 😊 Quote Link to comment Share on other sites More sharing options...
Amy Wade Posted August 25, 2022 Share Posted August 25, 2022 There were some helpful hints in a similar post I had done not long ago, not sure how much will be relevant to your Herald but it should help you with what bits will be required. Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 25, 2022 Author Share Posted August 25, 2022 Thank you Amy, that is a help 👍😊 Quote Link to comment Share on other sites More sharing options...
glang Posted August 25, 2022 Share Posted August 25, 2022 Yes it looks like the Spitfire 3 rail J type gearbox will go straight in as its splines, length, gearlever position will all be the same. My only doubt would be with the new gearbox coupling matching the existing propshaft one... 1 Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 25, 2022 Author Share Posted August 25, 2022 Thank you all advice gratefully received, I believe that I may have to change the propshaft or the flange and UJ on my own and a thinner mounting plate 👍 thank you 😊 Quote Link to comment Share on other sites More sharing options...
RobPearce Posted August 25, 2022 Share Posted August 25, 2022 3 minutes ago, Wendy Dawes said: I believe that I may have to change the propshaft or the flange and UJ on my own and a thinner mounting plate You will need to change the propshaft for any change to overdrive as the OD unit adds about two inches to the length of the gearbox. The J-type vs. D-type difference is much less - perhaps half an inch. However, a J-type will almost certainly have the large flange that takes 3/8" bolts, whereas a D-type may have the smaller 5/16" bolt type like your existing propshaft. 1 Quote Link to comment Share on other sites More sharing options...
JohnD Posted August 25, 2022 Share Posted August 25, 2022 It should, I think, bolt on. But you will need a shorter propshaft. Do you have electrics, esp. the steering column switch? Or one of those fancy gear knob switches? I couldn't be bothered with those when I put an O/d on my Vitesse. Instead I put a 'push-on, push-off' switch on the steering wheel, on a length of 'curlywhirly' cable that doesn't tangle, with an LED to remind me tha the O/d is switched on. 1 Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 25, 2022 Author Share Posted August 25, 2022 (edited) I’m just in the process of buying the gearbox don’t have it yet and so don’t have the overdrive switch yet, will probably have column mounted one as it’s more original for my Herald Edited August 25, 2022 by Wendy Dawes Quote Link to comment Share on other sites More sharing options...
glang Posted August 25, 2022 Share Posted August 25, 2022 3 hours ago, glang said: Yes it looks like the Spitfire 3 rail J type gearbox will go straight in as its splines, length, gearlever position will all be the same. My only doubt would be with the new gearbox coupling matching the existing propshaft one... Ha, sorry yes I meant your new box will be the same length as a D type OD box but of course youre starting with a non OD so according to the Canley Classics page you will need a prop 3.5" shorter... Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 26, 2022 Author Share Posted August 26, 2022 Thank you I think it’s a Vitesse O/D prop that I’ll need ill ring Canley and ask Dave good call hadn’t thought of that 👍😊 Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 26, 2022 Author Share Posted August 26, 2022 12 hours ago, RobPearce said: You will need to change the propshaft for any change to overdrive as the OD unit adds about two inches to the length of the gearbox. The J-type vs. D-type difference is much less - perhaps half an inch. However, a J-type will almost certainly have the large flange that takes 3/8" bolts, whereas a D-type may have the smaller 5/16" bolt type like your existing propshaft. Thank you Rob 👍 all a new minefield for me So nice to have expert advice from everyone on the forum x Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 26, 2022 Author Share Posted August 26, 2022 12 hours ago, JohnD said: It should, I think, bolt on. But you will need a shorter propshaft. Do you have electrics, esp. the steering column switch? Or one of those fancy gear knob switches? I couldn't be bothered with those when I put an O/d on my Vitesse. Instead I put a 'push-on, push-off' switch on the steering wheel, on a length of 'curlywhirly' cable that doesn't tangle, with an LED to remind me tha the O/d is switched on. Thank you John, all advice points to definitely a shorter prop shaft, I’ll have to start looking 😊 Quote Link to comment Share on other sites More sharing options...
Clive Posted August 26, 2022 Share Posted August 26, 2022 13 minutes ago, Wendy Dawes said: Thank you John, all advice points to definitely a shorter prop shaft, I’ll have to start looking 😊 If a D type, a vitesse non OD is the (about) correct length. But one end will have he wrong flange fitted. Which means swapping, which means it will very likely go out of balance. Just changing a UJ will cause an issue. Best bet is to measure the required length once fitted. Then I would be inclined to get a very good prop shortened (with sliding joint) OR get a new one made. Canley classics have the prop lengths listed for just about all combinations. https://www.canleyclassics.com/?archive=propshaft-problems Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 26, 2022 Author Share Posted August 26, 2022 Hi Clive Thanks for the info. x I'm thinking J type as D type are very expensive and hard to find I will contact Canley classics many thanks for the link to their website x Quote Link to comment Share on other sites More sharing options...
RobPearce Posted August 26, 2022 Share Posted August 26, 2022 Even with a J-type on a 3-rail box, it's still the non-OD Vitesse prop you want, it just compresses the sliding joint near its limit. The OD version wouldn't reach. The OD one may be correct for a single rail, I'm not sure on the length of that. Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 26, 2022 Author Share Posted August 26, 2022 Thanks Rob, that makes it easier to find one so grateful for your advice and sharing your knowledge thank you 🙏 Quote Link to comment Share on other sites More sharing options...
Clive Posted August 26, 2022 Share Posted August 26, 2022 3 hours ago, Wendy Dawes said: Hi Clive Thanks for the info. x I'm thinking J type as D type are very expensive and hard to find I will contact Canley classics many thanks for the link to their website x Wendy, do you mean the single rail j type from a 1500? The 3 rail j types are very rare, I have a bare od box but no adapter plate, od or gear remote. I also know somebody who can build what you want. He has some reconditioned d type overdrive units. Quote Link to comment Share on other sites More sharing options...
RobPearce Posted August 26, 2022 Share Posted August 26, 2022 23 minutes ago, Clive said: The 3 rail j types are very rare They were if you are discussing original factory equipment, but all three of mine have 3-rail with J-type as they were a popular conversion in the '90s. 1 Quote Link to comment Share on other sites More sharing options...
Clive Posted August 26, 2022 Share Posted August 26, 2022 2 minutes ago, RobPearce said: They were if you are discussing original factory equipment, but all three of mine have 3-rail with J-type as they were a popular conversion in the '90s. Fair point. Mr Kipping had a production line IIRC Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 26, 2022 Author Share Posted August 26, 2022 (edited) I have one available when I’m ready for it thank you Clive a 3 rail spitfire j type but if it falls through I’ll be in touch x👍 Edited August 26, 2022 by Wendy Dawes Quote Link to comment Share on other sites More sharing options...
glang Posted August 26, 2022 Share Posted August 26, 2022 1 hour ago, RobPearce said: They were if you are discussing original factory equipment, but all three of mine have 3-rail with J-type as they were a popular conversion in the '90s. I think most useful is whats available now and I would say at a very rough guess for units Ive seen advertised over the last few years its one J type 3 rail for every twenty or more D types or single rails... 1 Quote Link to comment Share on other sites More sharing options...
mpbarrett Posted August 26, 2022 Share Posted August 26, 2022 I have a 3 rail J type OD in my 13/60 Herald (now 1500 engine). I originally used non OD Vitesse prop shaft but had balance problems so brought a new prop shaft from CC. mike 1 Quote Link to comment Share on other sites More sharing options...
Wendy Dawes Posted August 26, 2022 Author Share Posted August 26, 2022 The advice is priceless on this forum, I’ll look for a prop-shaft, think a few local CT members know of some locally I think 👍 Quote Link to comment Share on other sites More sharing options...
glang Posted August 26, 2022 Share Posted August 26, 2022 1 hour ago, mpbarrett said: I have a 3 rail J type OD in my 13/60 Herald (now 1500 engine). I originally used non OD Vitesse prop shaft but had balance problems so brought a new prop shaft from CC. mike I take it you just got the standard 3 rail OD propshaft from CC as they dont seem to differentiate between D or J types? Quote Link to comment Share on other sites More sharing options...
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