V65 Gearbox replacement - help with ID number

[chrisk]

Hi, I'm looking at a replacement gearbox for my 1981/2 v65, the one I'm looking at is stamped D-002829

The guy says its from a v65, but it has marker pen  on it saying v50iii, v65/v75.  How do I know what it's actually from? I know that a v50iii and v65 have different ratios, not sure about a v75. Either way how can I tell what's it's from?

The was a post from MWRenn saying the following which probably means it's from a late v65???

" in 1983 MG updated the V65 and V65SP transmission gears and mainshaft with new parts, starting with number 2253. These are not interchangeable with transmissions before the update. Basically, the mainshaft is different, as well as 5th  4th, 2nd, and 1st gears on the mainshaft and layshaft"

Thanks

[wymple]

My son replaced the trans in his 84 V65 with one from a V50. There was a minor difference that I can't remember exactly. I will see him later today and get up to speed on what he did. It works fine.

[chrisk]

Ratios are definitely different between v50 and 65,  I checked I the manual...

[Antietam Classic Cycle]

"Early" input shaft has approx. 17 mm splines, "later" has 22 mm. Some V50 III and Monzas may have the 22 mm, but mostly it's found on V65 and V75/V7 'boxes. 

[SED]

Charlie does that mean you can adapt a 22mm spline 'box to a 17mm spline bike by swapping the clutch disc?

Thanks & Merry Christmas

[Antietam Classic Cycle]

Charlie does that mean you can adapt a 22mm spline 'box to a 17mm spline bike by swapping the clutch disc?

Thanks & Merry Christmas

I think that's all it would take. Not a small-block expert though. 

[SED]

Thanks Charlie! 

Also noticed this...

Ratios are definitely different between v50 and 65,  I checked I the manual...

This is true of the reduction ratio between the clutch and gearbox, but is it true of the gears themselves?

BTW pretty sure reduction ratio is the same for V65 and V50 Monza.

[Chuck in Indiana]

I think that's all it would take. Not a small-block expert though. 

Me, either, but I agree.
I put a Breva transmission in the Lario, and it was an easy swap. There are some differences, but nothing that will keep you from doing it. It has a *much* improved breather setup to boot.

[SED]

Me, either, but I agree.
I put a Breva transmission in the Lario, and it was an easy swap. There are some differences, but nothing that will keep you from doing it. It has a *much* improved breather setup to boot.

I remember that now!  Good to know.   

[Hymes Inc.]

My son replaced the trans in his 84 V65 with one from a V50. There was a minor difference that I can't remember exactly. I will see him later today and get up to speed on what he did. It works fine.

Dad is mistaken here. I bought a case section from a V50 because it looked similar but had a few small differences that made it not work. Ended up buying a complete transmission off ebay from a 1984 V65.