Triumph Repair: Spitfire Overdrive, overdive, gbox

Question
Jim, I have a good J type overdive on the back of a bad GT6 3 rail Gbox.   Can I take it off and fit it to my good 3 rail box currently in my MkIV Spit?   If so, what is required?

Answer
Russ,

The main difference between the overdrive/non-overdrive boxes is that the o/d gearbox has a shorter mainshaft, designed to slip into the o/d unit.

In theory you should be able to rebuild your Spitfire gearbox using a new mainshaft and the o/d should fit.  

You'll also need the wiring harness from the GT6 for the o/d controls.  Also you may need to use the trans mount plate from the GT6 as the o/d trans mount plate is almost flat whereas the stock mounting plate is bulged up where the trans mount is bolted in.


Cheers,

Jim