Rear Final Drive

Final Drive Ratios:

4.11:1Spitfire Mk1-3 (Mk3’s had two different input shafts during production run) (GA case #)
3.89:1Non-US Spitfire Mk4
3.89:1US Spitfire Mk4 (1971)
4:11:1US Spitfire Mk4 (1972)
3.89:1US Spitfire (73-74)
4.11:1US Spitfire Mk4
3.63:1Non-US Spitfire 1500
3.89:1US Spitfire 1500 (75-79)
3.27:1Swiss Spitfire 1500 (1980)
3.89:1GT6 with overdrive
3.27:1German GT6 with overdrive

3.89:1 Spitfire diffs have an FH prefix, 3.63:1’s have FR

4.875:1948cc Herald Saloon (G case #) (not interchangeable with 4:55:1)
4.55:1948cc Herald Coupe, Convertible and twin carb Saloon (Y case #) & Marina Van
3.63:1Dolomite 1850 (early) & Marina 1800
4.11:1Herald 1200 (had two different input shafts during production run) (GA case #)
4.11:1Vitesse 1600 (HB case #) & Toledo 1300 & Dolomite 1300
3.89:1Vitesse 2-liter & Toledo 1500
3.63:1TR7 (non-overdrive)
3.27:1TR7 auto (early)

Final Drive Lubricants:

Above 32 degrees F (0 degress C)SAE 90 Hypoid
Below 32 degrees F (0 degress C)SAE 80 Hypoid

It is essential to use an EP (extreme pressure) oil to GL4 spec only for the diff and overdrive. DO NOT USE GL5. Virtually all oils now sold are to GL5 spec and will “melt” the copper washers in the diff.

Final Drive Lubricant Capacity:

1.2 pints (0.6 quarts)1.0 Imperial pint0.57 liters

Driveshaft/Diff Flanges

Early Differential (up thru Mk3) have the smaller flanges that mate with the small flanges on the axles and Drive Shaft.

Early Gearbox (up through the Mk3) have the smaller flange to mate with the original smaller flange on the drive shaft.

Later Differential MkIV on have larger flange that mates with an equal sized driveshaft and axles.

Later Gearboxes MkIV on have the larger flange to mate with the same size flange on the drive shaft.

All GT6’s have the same size flanges as the later Spitfires on the Differential and gearbox.

Other Diff Numbers

SS sufix to the Diff Number – (Factory) Supplied Spare/replacement or “Special Systems”
SS designation mean the original item was changed before leaving the factory. I have seen many engines with this code but only a few rear ends.

Related Links

Diff Factory Service Manual page
The service manual for Triumph to use to service and rebuild differentials on early Spitfires, Heralds, and Vittese.