<VV> EM, LM speedometer question - add'l info

[Dan & Synde]

Hi Andy,

Yes, it will work but you will need a ratio correction box in between the
wheel and speedo to correct it.  The early speedo require a 1000 revs/mile
whereas the late speedos require 800 revs/mile.  That's 20 % difference.
Tire size is also a factor.  Speedo cable square drive is the same size.
You'll need to cobble something together to allow for the addition of the
ratio correction box between the speedo and wheel.  I ran into that same
issue when fixing the speedo drive on our Ultravan.  It has the same style
front wheel speedo drive that feeds a Spyder speedo.  I bought a 20% ratio
correction box and two cables.  The problem with the ratio correction boxes
is that they all have a 7/8" female thread on the input and a 7/8" male
thread on the output as they are designed to connect directly to the side of
a transmission.  Think about it, the early Corvair drive off the
differential is 7/8" male.  The output of the ratio box is no problem as you
can get a standard cable with the correct 7/8" female on one end and the
5/8" male on the other.  I had to get creative with the input cable that
went between the wheel and the ratio box.  What I did was make a 7/8" male
to female adapter and used the transmission end of a cable as the input to
the box.  Another problem is that most of the ratio correction boxes are
setup for a "tang" drive instead of the "square" drive.  Luckily, the ratio
correction box I bought came with an insert to adapt the "tang" drive to
"square" drive....but it would only work for the output side.   With the
input side, it would have been to far recessed because of the 7/8" female to
7/8" male adapter I had to make.  I solved that problem by using a special
"tang" to "square" drive adapter made by MSD for their distributers with
tach drive.  The adapter is made specifically for using their tach drive
distributers on the old Corvettes.  Worked perfect for my needs.

Sounds like a pain doesn't it !!  It works great though despite the
discouraging words I received from several online speedo shops.  They told
me it would never work and I would have all kinds of needle bounce with what
I was trying to do.  They wanted to sell me a new speedo.  Nope, I'm into
the old stuff and wanted to keep it that way.  It is smooth as smooth can be
and very accurate now.

If you are interested in pursuing it, check out
http://www.transmissioncenter.net/speedometer_calibration_______va.htm

Best place I found, actually with the help of Jim Davis, a fellow
Ultravanner.  Good prices.

Let me know if you want the part #'s of the cables and MSD tach drive
adapter I used.  You'll need to play for the correct ratio box though.  You
can get real close if you know the exact tires you are using and know the
rev/mile advertised by the manufacturer assuming your speedometer hasn't
been fussed with.  

Good luck,

Dan Kling

1961 Greenbrier Deluxe, 4spd, 3.89  On the Road Again,  yeehaw :)
1963 Spyder, restored   4spd Saginaw
1967 Ultravan #299  Newest of the herd!! Almost killed me already!!


http://www.flickr.com/photos/81412237@N00/sets/
A few pictures of the Greenbrier, UltraVan, engine and tranny tear down with
more to come! 



Andy K. said

>Unfortunately, I failed to mention that my friend plans to use a LM
transaxle; thus he can't use the EM >speedo cable.  So, do you believe a LM
speedo cable will drive an EM speedometer?