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[dpinkous]

I recently bought a 1971 spitfire with a 4 speed transmission. If I remember right, the guy told me that the 5spd/overdrive tranny he gave me was the original, which I would like to install. how would I tell what the original was? can anyone tell me what differences there are btwn the 4spd and 5spd(in drive shaft length, bolt arrangement, etc.) and what to look for in order to swap it out?

[herald948]

First, and to clarify, an original gearbox with overdrive is still a four-speed, although the overdrive unit essentially adds two additional ratios (one between 3rd and 4th and the other "beyond" 4th). Whether or not there is an overdrive unit attached to said gearbox, an original MkIV Spitfire gearbox should have an "FH" serial number prefix, and that serial number can be found on the top "face" of the main case, near the edge of the top cover. The "main" ratios of the gearbox are the same regardless.

If overdrive was original to the car, it should have a relay and some associated wiring in place. Note that the "on-off" switch, again if original to this car, would be a switch in the gear lever knob.

Otherwise, yes, the driveshaft would be a bit shorter on an OD-equipped car, and the rear mount setup is quite different. That's pretty much it, though.

[jrgambony]

A way to tell if the car HAD an overdrive originally is to look at the Commission # (typically used in the US as the "VIN" on your title).

If it ends in an "O" or an "OU" (US spec) then the car originally had an o/d from the factory.

If not.. then the o/d was something the previous owner picked up loose.


Cheers,

Jim
Dallas