OD compatability

[beamdream]

Hi all, looking for some collective wisdom on overdrives.

I have come across a Series 1 gearbox (non syncro 1st) complete with overdrive; in my shed I have a later all syncro non OD gearbox. Is it possible to install the OD unit on my all syncro box ?

I can cope with diff ratio, tail shaft length and the necessary electrics required, are there any other pitfalls that others have encountered ??

 

[gary1725]

Hi Beamdream,

Not easily is the short answer!

The output shaft on the OD gearboxes is different from Non OD cars - length is different and it has a cam on the shaft it to drive the overdrive pump. If however you can find a SV OD output shaft that matches your gearbox and swap them - then yes the OD will work.

I am not sure of the differences between SV boxes as far as "did they change the internals" that would prevent what I described - the other option of course is to rebuild and use the Early gearbox and OD - then the only changes will be swapping over the release fork and pedestal and shortening the drive shaft, finding a column switch and an OD relay.

Thanks
Gary

 

[pruyter]

Hi,

I don't like to write this, but this plan is going to fail. A few months ago I had exactly the same plan and I asked John Roseby, the well known Britisch expert in this field, if my plan was achievable and his answer was a clear "No". The reason for this are the different internals of both boxes.

Regards,

Peter

 

[RootesRacer]

You can however modify an early OD mainshaft to fit a later OD gearbox.

Not trivial though.

 

[beamdream]

Thanks RR, can you elaborate on the not trivial ?

And thanks Garry, yes I was considering the swap to include the S1 output shaft but Rootes may scuttle that for me.

 

[RootesRacer]

Thanks RR, can you elaborate on the not trivial ?

It involves some welding and machining to make the earlier shaft functional in a later box.

Having an non-sync OD mainshaft, an all-sinc non OD mainshaft together on a table (with micrometer and caliper) would let you see the dimensional differences to the extent that a machine shop could do the work.

Its my understanding this was a more common modification back in the day as the all-sync main shaft is quite a bit thinner in cross section and spirited driving (clutch dumps) could and did result in twisting the mainshaft on the later more fragile later mainshafts.

 

[Tom H]

Beamdream,

I think the practical solution is to choose either the all synchro box or the OD box. If you plan to do any fairly long drives, the OD is a great trade off against the synchro first gear.

And if you cannot find an original column switch and relay set for your OD you can probably find some reasonable substitutes.

Tom

 

[beamdream]

Thanks Tom, RR.

I do have an odd OD shaft sitting in a pile of bits, not sure what it came out of

Now that I see its not a straight swap I might dismantle the non syncro OD box and compare the two shafts, thanks RR, now that I know what to look for, with a bit of luck I may be able to cobble together a syncro OD unit.

Tom I think I will fall back to your suggestion of fitting the non sync OD box if the other exercise fails; the electrics I can cope with using substitutes.