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Spitfire Spitfire Trans Swap...

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lilwetcowboy

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I have a 1969 Spitfire MK3 with overdrive. The current (original) transmission has no synchro into first gear so I was hoping to swap in a trans from a later model (1500?) but was wondering if it is just a bolt on job or do I need to change bell housing, drive shafts, mounts, etc?
 
What kind of propeller shaft (driveshaft) do you have? Does it have the sliding splines, or the straps, or ???? If it slides, it might adjust enough. I admit I don't know the size of the output flange on an original non-synchro-first, three-rail OD gearbox; it might be smaller than the output flange of either the three-rail (1971-74) or single-rail (1975-on) gearbox, unless said later gearbox also has OD.

Regardless, a non-OD gearbox will have a different rear mount plate and mounts. The bellhousing is the same, and the input shaft is the same if you stay with a later three-rail. It will require a different clutch driven plate if you use a single-rail, as the input shaft is different.

Unless you are planning on a later gearbox WITH the overdrive (and you can't just swap that over to the new gearbox without the correct mainshaft, etc.), I would advise against the change. Not having a synchro first gear is NOT the worst thing in the world; it is far easier and cheaper to either learn to double-clutch down to first, come to a stop before engaging first, or just relying on the torque of the engine to struggle a wee bit at very low speed in second gear!
 
I just put a later single rail gearbox with a J-type OD into a 69 Spit. I changed the flywheel to a later 1500 and used the clutch setup from a later 1500 too. The driveshaft (original non-OD 3 rail) needed to be shortened and I used the flange from a GT6 driveshaft on the front end of it to mate to the gearbox. The J-type rear mount worked with the original mount plate with slight modification. I feel that the single rail has a nicer shifter set up in addition to the synchro on 1st.


Erik Nygaard
Her Majesty's Auto Service
 
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