I found the article on the 311s.org page:
I have a 68 1600 but have put the 5 spd trans. I have also put 195/60 15
Panasport wheels. Is there a formula that I can use to figure out which
pinion I need to purchase to get the correct speed with the change in the
above two changes? Does anyone know of a distributor that would have the
correct size?
Thanks
Chuck
311s SPEEDO-TRANNY-GEAR
reprinted with the author's permission
Ross Mullen of Sports Imports writes:
The 4 speed and 5 speed transmissions in roadsters drive the speedo cable by
the same method. A plastic toothed gear which is color coded and comes in
variations 16-23 teeth. Each tooth variation gives roughly a 10% change in
speedo readings. This gear is located at the transmission end of the speedo
cable and can be changed with transmission in car. It is best to drain the
oil before removing the gear which is held in place by a 10 mm bolt and
small tab. before removing, estimate the inaccuracy by having someone pace
you and measure what your gauge reads when they are doing 50 mph. If yours
reads 55 then you are out 10%( 50 x 2=100 5X 2=10%) Most 5 speeds come with
18 tooth gear normally yellow. Dropping or adding a tooth will compensate to
make your a speedometer a little closer to accurate.
5 speed transmission FS5C71A gear part numbers
32703-78100 16 tooth
32703-78101 17 tooth
32703-78102 18 tooth
32703-78103 19 tooth
32707-78000 sleeve for 16-19 tooth
32707-66300 sleeve for 20-23 teeth
32703-78104 20 tooth
32703-86401 21 tooth
32703-86402 22 tooth
32703-86403 23 tooth
4 speed transmission F4C63L gear part numbers
32703-22000 16 tooth
32703-22001 17 tooth
32703-21100 18 tooth
32703-78600 19 tooth
32707-14600 sleeve for 16-19 tooth
32707-14810 sleeve for 20-23 tooth
32703-14816 20 tooth
32703-25031 21 tooth
32703-16715 22 tooth
32703-19910 23 tooth
Increasing the tooth count on the pinion will decrease the MPH count. In
other words, a 10% off 55 MPH reading with an 18 tooth pinion gear can
correctly read 50 MPH by installing a 19 tooth pinion gear. Ross Mullen
sports imports.
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