Spitfire overdrive

[AndyCrews]

I'm sure this must have been covered before so apologies if I'm repeating stuff.

 

I'd like to fit an overdrive to my '78 Spitfire 1500 to give a more relaxed drive, currently anything over 55mph is a loud drone.

 

Is it just a case of changing the box for an OD unit along with the wiring, or are there more parts required?

 

The other question I have, is where would be the best place to source box. Any recommended suppliers or is it best to advertise or somewhere like the Spitfire Graveyard?

 

Any replies appreciated.

 

Andy

 

 

 

 

[Mjit]

Few more bits to it than that.  From memory:

• Different gearstick (with O/D switch).  If it doesn't come with the box you could mount the O/D switch anywhere/extend wiring to suit.
• O/D extension loom.  Just 2 wires to run from bulkhead to base of gearstick so can make this yourself.
• Speedo drive cable.  Drive it slightly further back than non-O/D so need slightly longer cable.
• Speedo angle drive.
• O/D prop. shaft.  O/D box is slightly longer so you need a slightly shorter prop.

Can't think of anything else.

[Jezza]

Different ratio rear diff?  I had the difficulty of finding a non-OD diff when needing to replace mine on my GT6, so I assume there is a different ratio for an OD box. Not sure if its the same story on a Spit though.

[Pete Lewis]

as a 1500  I guess you have a single rail box,  reverse is right gate and forwards ?? which was mated to a J type OD. 

 

if modifying your own box you need a mainshaft, adaptor casting, and  the remote needs to  to operate the inhibitor switch 

think Single rail + OD has a different remote and support  you need rear mount and chassis support plate 

 

if looking for a replacement box 3 rail and D type  will be easier, but you need a input shaft with a rolled spline,

 

if buying a OD  Unit ouright look at OD repairs sheffield or OD Spares Rugby 

 

if you need someone to do the full rebuild then from the Courier Mike Papworth   is the man 

 

024 76644499/07  will make up whatever you want 

 

even install it with photo's 

 

Pete

[clive]

Diff the same on all spitfires, only GT6 had the 2 ratios.

Gearbox rubber mount and plate are also on the "needed" list.

[clive]

I ought to clarify that^^

 

spitfires didn't change ratio depending on whether OD was fitted or not. But before anybody points out the bleeding obvious, MK 1-3 all had 4.11, MK4 3.89 and 1500 3.63!

[Pete Lewis]

A thought if its a loud drone maybe a change to the exhaust is the real problem to address

certainly easier

 

pete

[mishmosh]

Dont forget the gearbox mounting plate.

[AidanT]

If you are looking to purchase a refurbished unit to either fit yourself or get fully fitted then I can recommend Mike Papworth. Great guy and very helpful with aftercare . His details are in the Courier

 

Aidan

[AndyCrews]

Many thanks for the replies. Lots of info to consider.

 

Andy