Ron,
I think there is probably some information in the archives on this but the
summary of the causes of a bouncing speedometer can be two things:
1. the speedometer cable is kinked in some way causing it to repeatedly
stick, wind up and let go, then stick again, etc. The best way to check for
this is to completely withdraw the inner core and lay it on a clean flat
surface. Bring the ends almost together in a large loop. Carefully turn one
end while the cable is remaining completely flat on the table surface. Watch
to see if the other end is lifting and flopping at all at the end or
anywhere along its length. Ideally it should lie completely flat and turn
smoothly.
2. there is excessive lubricant that has travelled up the cable and entered
into the speedometer head. This is most commonly caused by oil escaping past
a worn seal in the brass sleeve that the 90 degree gear drive screws into on
the side of the overdrive unit. Most people don't realize that there is a
seal within the brass drive sleeve. When worn, gearbox oil can escape and
travel right up the cable like an auger, and enter the speedo, causing the
problem.
I deal only with Nissonger Instruments (long story). When they encounter
this oil contamination problem they clean and test the unit and return it
with a preprinted warranty label stating the problem and that it must be
fixed on the car or their cleaning repair warranty will not be honoured.
Rich
-----Original Message-----
From: healeys-bounces at autox.team.net [mailto:healeys-bounces at
autox.team.net]
On Behalf Of Ron Ray
Sent: 2011-05-01 9:52
To: 'healeylist'
Subject: [Healeys] Bouncing Speedometer
Folks,
Recently I replaced the angle drive on my 1959 3000 in hopes of eliminating
the factory optional bouncing speedometer.
While this did result in somewhat less bouncing, it is far from the results
I had hoped for.
The speedometer was rebuilt twice by MO MA a few years ago, after the
initial rebuild failed to correct problems with the odometer. The second
attempt by MO MA simply changed one odometer problem to another odometer
problem, so I gave up n MO MA.
The speedometer cable is relative new and the distance the cable extends
into the speedometer is correct per Norm Nock's book.
Any suggestions?
Thanks
Ron
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