Mk3 spitffire overdrive conversion

[phillip ridley]

Hello advice needed I would like to convert my mk3 Spitty to overdrive is there more than one type off gear box and witch one would be the best to try and find thanks .phill

[Nick Moore]

I think Mk3 Spitfires had the '3 rail' box with no synchro on first. If so, overdrive versions had a D Type overdrive. Later on, Triumph introduced the 'single rail' box with synchro on all forward gears. I'm not sure if these had D or J type overdrives - perhaps both?

As to which you should fit, I kinda like the three rail boxes and so if your car had one of those, I'd fit a three rail with D type box. They're strong enough.

It's possible to add an overdrive to a gearbox, but you need the adapter casting, and a different gearbox output shaft. Complete gearboxes are out there, but the trick is being sure you've found a good one.

[DanM]

You can use an early 3 syncro with d type overdrive or the later mk4 with 4 syncro which mainly came with a dtype but the very last had a jtype. You could also use the 1500 single rail but this would need a different clutch plate. You will also need the od propshaft and if you get a mk4 box and prop the rear flange needs swapping. (standard 1500 prop is the same length I think), mounting plate and switch (you could use the stick mounted mk4/1500 or get a column switch)

[phillip ridley]

Quoted from Nick Moore

I think Mk3 Spitfires had the '3 rail' box with no synchro on first. If so, overdrive versions had a D Type overdrive. Later on, Triumph introduced the 'single rail' box with synchro on all forward gears. I'm not sure if these had D or J type overdrives - perhaps both?

As to which you should fit, I kinda like the three rail boxes and so if your car had one of those, I'd fit a three rail with D type box. They're strong enough.

It's possible to add an overdrive to a gearbox, but you need the adapter casting, and a different gearbox output shaft. Complete gearboxes are out there, but the trick is being sure you've found a good one.

thanks for the help a lot to take in many thanks .phill

[phillip ridley]

Quoted from DanM

You can use an early 3 syncro with d type overdrive or the later mk4 with 4 syncro which mainly came with a dtype but the very last had a jtype. You could also use the 1500 single rail but this would need a different clutch plate. You will also need the od propshaft and if you get a mk4 box and prop the rear flange needs swapping. (standard 1500 prop is the same length I think), mounting plate and switch (you could use the stick mounted mk4/1500 or get a column switch)

Thanks for that a lot to take in cheer.phill

[hollidaysc]

if you do go for a Mk4 3 rail dtype OD box you'll lose the whinning first gear (no good if you have hooligan tendencies), which I miss since converting my Mk3

[Dogsbody47uk]

I have a 13/60 saloon J reg, big crank GK engine. I have fitted a 1500 Spit flywheel, clutch and overdrive gearbox. It's great. It needed the od box, 1500 flywheel, bolt sleeves to fit the flywheel to the crankshaft (from Rimmers), 1500 clutch, larger than 13/60 original ( no bad thing) , modified propshaft from Canley Classics, appropriate rear gearbox mounting, and od switching mechanism. I use the switch in the gear lever method but you can use the column mounted switch as per the Vitesse if you prefer. The advantages are a higher first gear and lower revs at cruising speed, so less noise and better fuel consumption, typically 35 to 36mpg for my 13/60. I tend to thrash her.

[phillip ridley]

Quoted from hollidaysc

if you do go for a Mk4 3 rail dtype OD box you'll lose the whinning first gear (no good if you have hooligan tendencies), which I miss since converting my Mk3

Thanks for that I am a bit heavy footed when wife's not in the passenger seat so would need one that could take the strain cheers phill

[phillip ridley]

Quoted from Dogsbody47uk

I have a 13/60 saloon J reg, big crank GK engine. I have fitted a 1500 Spit flywheel, clutch and overdrive gearbox. It's great. It needed the od box, 1500 flywheel, bolt sleeves to fit the flywheel to the crankshaft (from Rimmers), 1500 clutch, larger than 13/60 original ( no bad thing) , modified propshaft from Canley Classics, appropriate rear gearbox mounting, and od switching mechanism. I use the switch in the gear lever method but you can use the column mounted switch as per the Vitesse if you prefer. The advantages are a higher first gear and lower revs at cruising speed, so less noise and better fuel consumption, typically 35 to 36mpg for my 13/60. I tend to thrash her.

Thanks for the info I will this to hand when find the right direction to go and get my round  thanks.phill