Triumph Repair: Spitfire Differential, bolt flange, bolt holes

Question
Hi Scott, I hope all of this makes sense. I have a Lotus Locost that is built on a 1971 left hand drive spitfire frame, drive train and engine. Last weekend all kinds of things went wrong around the axles and differential.Everywhere when there was a 4 bolt flange that bolted into another 4 bolt flange leading to the differential, they sheared (these are circular flanges with 4 bolts that connect at various times to the axle, leading to the differential). It did not look to serious until I saw that it sheared the bolts (allen bolts?)on the flange that bolts to the differential. The some of the bolts are broken in the differential housing, or the the bolt holes could be damaged.

I hope to be able to remove the sheared bolts that are now in the differential housing. If I can't I have to get another differential. If this happens I have a couple of questions:1) Are left hand drive and right hand drive differentials different? 2) Are all the Spitfire differentials the same, or do I have to buy one from a Mark IV ?

Thanks for your help.

Scott B.

There is a 4 bolt flange at the end of the axle that bolts onto the splined flange that goes into the differential.

Answer
All spitfire differentials have the same mountings to the frame.  The early spits and GT6 differentials were "fixed" spring, and had 6 mounting studs for the spring.  The later spits had 4 mounting studs for the "swing" spring.  Early MkI & MkII spits may have had squared, smaller flanges for the drive shaft.

The rear diff cover, which houses the stub axles and the spring mounting, can be replaced, and the gearset with pinion retained.

I'm not aware of a difference in LH vs. RD drive differentials.   Your easiest replacement would be to find another 3.89 late model differential, which will likely be a bolt up.  If you buy an earlier 4.11, you may have to change the pinion flange.