Bruce:
I found this in my file of list posts - Ross Mullen's tutorial on speedo drive
gears:
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 numbers
32703-78100 16
32703-78101 17
32703-78102 18
32703-78104 19
32707-78000 sleeve for 16-19
32707-66300 sleeve for 20-23 teeth
32703-78104 20
32703-86401 21
32703-86402 22
32703-86403 23
4 speed transmission F4C63L
32703-22000 16
32703-22001 17
32703-21100 18
32703-78600 19
32707-14600 sleeve for 16-19 tooth
32707-14810 sleeve for 20-23 tooth
32703-14816 20
32703-25031 21
32703-16715 22
32703-19910 23
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.
Mike Poorboy wrote:
> Bruce Dalrymple wrote:
>
> > Dennis....... sorry to hear about your lost wheel incident.
> >
> > I recently (last week) put a rebuilt transmission in my roadster that I
> > got from Dennis / Les @ CDM. It works great, my only problem is I think
> > my speedometer is off by 10 - 15 mph. My speedometer never worked
> > before , but I figured that 4k rpm = approxamately 80 mph. My
> > speedometer reads 95 mph at 4k rpm. Any ideals?
>
> Bruce,
> The formula for MPH, is the following MPH= rpm x tire diameter divided by
> (gear ratio x 336). Your gear ratio should be 3.90 in fourth gear with
> standard 1600 gearing.
>
> Mike
> 2 69 2000's
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