aknight123456 Posted January 13, 2021 Share Posted January 13, 2021 Morning all, I've got myself a donor herald which has a MK3 spitfire engine with a 1500 single rail gearbox and J type overdrive already fitted. The herald is a wreck so I want to remove the engine and gearbox to put them in my MK3 spitfire. Obviously the propshaft will not be the right size in the herald at the moment. I've found online the various lengths of propshaft for different Mks of spitfire but I haven't found any dimensions so you can mix and match. Can anyone confirm what size propshaft I'd need? I assume the difference of length is down to the single rail box being a bit bigger than the 3 rail so using a 1500 overdrive propshaft should work but I don't know if anything else factors into this. Cheers for your help! Quote Link to comment Share on other sites More sharing options...
glang Posted January 13, 2021 Share Posted January 13, 2021 This site has some useful info: https://www.canleyclassics.com/?archive=propshaft-problems Quote Link to comment Share on other sites More sharing options...
aknight123456 Posted January 13, 2021 Author Share Posted January 13, 2021 Hi Tight wad, I've seen the stuff on canleys website but I was looking for clarification that the difference in size of the propshaft is down to the size of the gearbox+overdrive and not some other factor that was changed between the mk1-4 and the 1500. Cheers Quote Link to comment Share on other sites More sharing options...
glang Posted January 13, 2021 Share Posted January 13, 2021 Well according to that info the early Spitfires with 3 rail OD boxes had a propshaft 1" longer than the later ones fitted with the single rail unit. The Herald data also confirms a 1" length difference between these two types of gearboxes hence there isnt be any other factor involved... Quote Link to comment Share on other sites More sharing options...
aknight123456 Posted January 13, 2021 Author Share Posted January 13, 2021 Oh excellent thank you, I hadn't actually clocked the herald figures so hadn't put two and two together! Hopefully that'll be the answer then. Many thanks. Quote Link to comment Share on other sites More sharing options...
Clive Posted January 14, 2021 Share Posted January 14, 2021 Quoted from aknight123456- Morning all, I've got myself a donor herald which has a MK3 spitfire engine with a 1500 single rail gearbox and J type overdrive already fitted. The herald is a wreck so I want to remove the engine and gearbox to put them in my MK3 spitfire. Obviously the propshaft will not be the right size in the herald at the moment. I've found online the various lengths of propshaft for different Mks of spitfire but I haven't found any dimensions so you can mix and match. Can anyone confirm what size propshaft I'd need? I assume the difference of length is down to the single rail box being a bit bigger than the 3 rail so using a 1500 overdrive propshaft should work but I don't know if anything else factors into this. Cheers for your help! You need spitfire 1500 od length prop, but (assuming you have the mk3 diff, squarish front flange, 1/2" spanner bolts) you need the mk3 type rear flange on the prop. In all honesty, I would buy new for a propshaft. An out of balance prop makes life miserable, and swapping UJs let alone a flange can put it out (real experience) and a 45 year old prop with a CV joint will probably be beyond its best. Get it in the car, measure, then call Dave Mac.... Quote Link to comment Share on other sites More sharing options...
aknight123456 Posted January 15, 2021 Author Share Posted January 15, 2021 Thanks for the info Clive! Yeah I'm definitely getting a new propshaft, hadn't thought about the flange though! Just curious...who's Dave Mac? 😅 Quote Link to comment Share on other sites More sharing options...
glang Posted January 16, 2021 Share Posted January 16, 2021 Dave Mac propshafts who manufacture and overhaul propshafts in Coventry. As a guide James Paddock does new 1500 OD props for 110 +vat and then of course, as Clive says, youd have to change over the rear flange. However an alternative to this would be to swop to a higher ratio 3.89 diff from another Triumph model as these have the same case but with a 1500 flange. This would only worth doing if you want to reduce your engine revs for cruising and its probably best to get advice from others as to the suitability... Quote Link to comment Share on other sites More sharing options...
thescrapman Posted January 24, 2021 Share Posted January 24, 2021 Changing to a 3.89 doesn't make much difference to revs as the change from the original cross-ply tyres to modern radials will have lowered gearing slightly, so you are just compensating slightly Quote Link to comment Share on other sites More sharing options...
Clive Posted January 24, 2021 Share Posted January 24, 2021 Quoted from glang- Dave Mac propshafts who manufacture and overhaul propshafts in Coventry. As a guide James Paddock does new 1500 OD props for 110 +vat and then of course, as Clive says, youd have to change over the rear flange. However an alternative to this would be to swop to a higher ratio 3.89 diff from another Triumph model as these have the same case but with a 1500 flange. This would only worth doing if you want to reduce your engine revs for cruising and its probably best to get advice from others as to the suitability... Don't swap a flange on a prop, it will put it out of balance (changing a UJ can do it, these cars are very sensitive) Hence getting it made with the correct flanges in the first place. I have seen the "round flange" diffs with extra drillings in teh flange so they will take the prop from a mk3 spit/herald etc. Not sure if a prop can be done in the same way though. Quote Link to comment Share on other sites More sharing options...
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