Triumph Repair: Triumph differentials, triumph spitfire 1500, british car club

Question
Can I improve the speed of my Spitfire 1500 by changing the differential to a higher gear ratio? Is there a differential available to upgrade the speed of my Triumph Spitfire 1500?

Answer
Hi Benjamin,
Do you mean cruise speed? The Spitfire normally has to run at a high RPM to run on the US expressways so many look for higher gear ratios. For example, Moss Motors sells a "Non-US" ring and pinion for $438.95. It is 3.63 to 1 ratio which is a little higher than the US version at 3.89 to 1. By the time you pay for bearings and seals and labor, you may be better off searching for a used overdrive gearbox. Local British car club and possibly E-Bay would be places to check along with many Internet sites. I'm sure there were some higher ratios ring and pinions used in racing but they might be hard to find.
Howard