overdrive gearboxes

[Roger]

I have a Vitesse with a D type overdrive box that is playing up. I have been told that the J type box from a Dolomite 1850 will fit in place of the D type. Has anyone done this conversion & know whats involved. ??)

[Nick Jones]

Roger,

I would think that your first step should be to see if your D-type cannot be fixed.  Problems are often electrical and relatively easy to sort.  Perhaps a bit of detail on the 'playing up' will yield a suggestion from the forum.

Ultimately the J-type is stronger and more reliable.  As to being a straight swap -  depends whether you mean putting the J-type overdrive onto the back of your existing box or a complete box swap.

First thing to note is that there are two different gearboxes fitted to the 1850 Dolly (although many of the internals are interchangeable).

Early cars have a 3 rail box (like the Vitesse) with the J type OD.  They are the same overall length as the Vitesse box and can be swapped without too much bother - just swap bell housings and be prepared for some monkeying with the rear mounting.  This is also the box type you would need to source the both the overdrive and adaptor plate, were you considering converting your existing box BUT I'm pretty sure the splines are different on D and J type (perhaps someone can confirm or deny!) meaning you will need to change the mainshaft too which means a complete stripdown, so you might as well swap the whole box.

Later 1850s have a single rail gearbox.  These are about an inch longer than the Vitesse box (the adaptor plate is longer for some weird reason) and cannot accept a Vitesse bell  housing (1850 is completely different).  The only way to make use of these is strip them and build them into the 3 rail casing.  Even then you still have the extra length to contend with, which means a shortened propshaft and more hassle with the mounting and possibly a bit of floor and chassis rail trimming.  You will also need the Dolomite fine spline clutch plate.  Advantages of this route is that the box is a bit stronger and more plentiful.  Early 3 rail types are hard to find -  I took the latter route about 15 years ago because I couldn't find an early one!


Hope this helps a bit!

[martin]

is it possible to put a vitesse 1600 overdrive box in a 13/60 herald?

[Nick Jones]

Martin,

Anything is possible given enough time & money.  However this is not an easy conversion as the gearbox input shaft is different.

The easiest route is the Spitfire box, preferably the MK4 4 synchro either with D type or, more desirable but rarer, with J type.

You would also need a shorter propshaft (Vitesse non-overdrive is the right length I think), mounting plate and mounting itself plus a right angle speedo drive (may be a cable too) and a few other odds and ends.
It is possible to use the Spit 1500/Dolly 1500 but this needs a different clutch plate and a specially made shorter propshaft (and is very heavy).

Quite a bit of work but very worthwhile - really transforms the cars cruising ability.  Canley and others do conversion kits.

Hope this helps

[heraldcoupe]

The Spitfire 3-synchro D-type box requires a 46.5" propshaft. The one fitted to a non-overdrive Vitesse is 47" long, the same propshaft is used in both overdrive and non-overdrive Triumph 2000, so they are another source. There is some depate over whether the 0.5" difference is a problem, I have done this conversion more than once without problems, but there may be issues on some cars where the splined shft is right at the end of it's compression.
The 4-synchro MkIV Spitfire gearbox is 0.5" longer than the earlier 3-synchro types, which would seem to rule out the Vitesse/2000 propshaft. I don't know the length of the 3-rail J-type box as I've never got my hands on one,
Cheers,
Bill.

[martin]

thanks nick and bill,
it's just an idea as i have a 1600 vit o/d box spare and a 13/60 thats just passed it's MOT.

[heraldcoupe]

The 1600 Vitesse box is fairly scarce, maybe you could find someone who wants to swap?
Cheers,
Bill.

[martin]

bill i have 2, one good one useable but needs rebuild.
both of them came in 2 litre mk 2 vitesse?

i would swap but i really would like a proper o/d box for my 2litre vitesse.