Triumph Repair: 1500 j type with over drive, Spitfire, herald

Question
I have got a gearbox from a 1500 spitfire its a laycock J type with overdrive on 3rd and 4Th gears, I want to fit it on to my 1360 triumph herald but i have been told its not that straight forward, I would be grateful if you could tell me how to go about this
          regards Geoff

Answer
Geoff,

As a swap it's usually easier to take the complete engine and trans as the flywheels and clutch setups did change over the years.

I'm not a Herald expert but I believe you have the small bearing 1296?   If so, you would have originally had the 3 rail gearbox.

The single rail J-type has a 20spline input shaft vs the 10 spline on the early cars.  Some of the specialty dealers used to offer a clutch disc in the correct diameter for the 1296 but with the 20 spline hole for the input shaft of the single rail gearbox.

If you can't find that particular clutch disk then you'll be forced to use the flywheel from the 1500 engine.  In order to fit a 1500 flywheel you'd either have to have the flywheel bolt holes in the crank oversized or use bushings designed allow the 1500 flywheel to be fitted to the 1296 crank.

You'll also need to shorted the Herald drive shaft and have a flange from a 1500 fitted to the transmission end.


Cheers,

Jim