Jeff McNeal wrote:
>
> Hi Kevin,
>
> I just bought one and have it sitting on my workbench, so I can help you with
> your question. The Mk3 (and MkIV) transmissions were both three-rail affairs,
> though the MkIV is really a different gearbox with full synchro in all forward
> gears, unlike the Mk3, which only had synchros in gears 2,3, and 4. The
> overdrive unit is clearly marked with a metal plate that identifies it as a
> Laycock de Normanville D Type. Later MkIV's switched from D-type overdrives
> to the more reliable J type, which was also adopted for the 1500 series and
> continued through the end of the Spitfire production run. The MkIV
> transmission with the D or especially J type O/D are considered to be one of
> the nicest bolt on enhancements to Mk3's, since you not only gain overdrive,
> but full synchro capabilities as well. Hope this helps.
>
>
I might add the following:
The MkIV gearbox is a little longer than the Mk3 owing to the extra
synchronizer in first gear. So if you use a full synchro 3-rail with OD, the
driveshaft will need to be a bit shorter than a stock Mk3 gearbox with
overdrive.
Joe
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