JSPM Close Ratio Gearset for TR4-TR6 gearbox

JSPM Close Ratio Gearset for Triumph TR4 - TR6 gearbox. (gearbox not inlcuded)

• Using an early (pre-1973) gearbox: 1st:  3.14 / 2nd: 1.63 / 3rd: 1.24 / 4th: 1
• Using a late (1973-on) gearbox: 1st: 2.99 / 2nd: 1.71 / 3rd: 1.29 / 4th: 1
• First gear ratio remains as stock, making it much easier to move around the paddock and grid vs the tall first gear that was used in the “Sprint” gearset.
• Subtle changes to the 1st / 2nd / 3rd ratios can be made if an early or late gearbox is used as the starting point.
• The second gear is designed to use the late, one piece steel top hat bushing, along with the thicker, less failure prone 2nd gear thrust washer.
• On the synchro mating surface, I have reduced the undercut at the gear, and also reduced the end chamfer.  This increases the contact area to the synchro ring, for maximum friction. 
• With the increased diameter of 2nd gear (on the laygear), a small amount of material must be removed from the support bridge for the reverse idler shaft to allow for clearance.
• A small amount of thickness has been added to the layshaft gears to simplify the process of adjusting the laygear endfloat to the minimum spec. 
  • In the past, a custom distance piece was required in some cases to achieve endfloat at the minimum end of spec. 
  • With this new design, the standard distance piece will need to be machined shorter during setup to adjust endfloat. 
  • This is a simple manual lathe operation.  For anyone who does not have access to this capability, we could easily handle this by mail.