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GT-6 trans/OD


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I am restoring a 1967 GT-6. I would like to use my GT-6 MK III trans and Type J OD. The question concerts the main shaft. Please check the photo. This shows a GT-6 mail shaft and a Spitfire 1500 mains haft. I think a could use the spit shaft however the front is too large to fit into the GT-6 input shaft. I wonder : 1) Is there a spit mains haft with this smaller end 2) Cullen I machine down the 1500 shaft so it would fit

Any comments would be appreciated


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the gt6 small spigot already looks tired this is the weakest link in the gearboxes the 1500 has the 18mm spigot used also on dolomite 1850 

and has much more capacity,  you must not grind the 18mm  down to 0.5"  or you loose the case hardening.


if converting to a 1850 input shaft you need a rolled spline clutch disc to match or get a 10 cut spline input shaft from mike papworth who has some made., there are tooth profile changes about through the evolution and you cant mix them, unless you like a lot of whining.


i would avoid the small spigot shaft if you want to get some life expectancy out of the rebuild


do make sure you dont forget the oil pump woodruff key and the flat sprung anti clatter circlip thats on a groove in the shaft,  these get missed frequently.





just checked and 3 rail mainshaft is TKC923

single rail      mainshaft is      RKC767


from rouges gallery im sure the 1st 2nd hub spline is very different size as a single rail hub is a right sloppy fit on a 3 rail shaft

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Thanks for the info. I am a relative Newby to British cars.

I agree the small spigot GT-6 shaft looks worn, however the other larger input shaft I have has a different gear size.

I was afraid that machining the 1500 shaft would destroy the surface hardening.

I am unaware of "Rouge gallery". Are the shaft numbers you mentioned from this group?


Terry Thomas


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There are the two shafts , you cant run some of the hubs from a gt6 3rail on a single rail mainshaft

The hub splines are either too small or rattling good fit.


If the box is stripped do a test fit the 1st 2nd hub from the 3 rail onto the 1 rail shaft


Having built many a gearbox from little triumphs to 18speed trucks my last spigot failure got me up to mike papworth and had the 18mm spigot and deadicated input stem wheel fitted

, sold now but its the only upgrade that works unless you go for a ford type 9 conversion

or TR7 small box.

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