Hi Derf,
You're right, the 1376 speedos were fitted to the cars with 1275 engines and
3.9 difs. along with 145-82 X 13 tires. These tires gave a wheel RPM of
about 930 + or - a few. The 4.22 dif cars had 1472 speedos.
The Brits had their own method of calibrating the speedos and used gearing
inside the speedo head to get the needle close enough to right and the
odometer sorta OK. The rest of the world was starting to standardize on the
1000 speed cable input and this method employed changes in the speedo worm
drive and sector in the transmission. The sector gear for cars that came
from the factory with same power trains but different tire sizes or dif
ratios typically had a sector colored differently, either by paint or dye in
nylon.
So the 1000 speedo you have is from cars that conformed to the rest of the
worlds standards as far as cable counts were concerned. If you want to use
it and get the proper reading in the Spridgets we play with, and the rib or
smooth case gearbox, you'll need an external cable gear box to reduce the
output to 1000.
Paul A
----- Original Message -----
From: "derf" <derf247@gmail.com>
To: "Spridgets" <spridgets@autox.team.net>
Sent: Wednesday, January 17, 2007 9:20 AM
Subject: Speedo Numbers
> What are the correct rear end/speedo ratio numbers?
> I've got a couple of 1376 speedos and a 1000. I have several different
rear
> end ratios around.
> The 1376s are from early 70s models so I figure that 1376 should match
with
> 3.9 diffs.
> Cheers,
> Derf
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