<VV> Speedometer problem on 63 Monza
cmckinley313 at cox.net
Fri Apr 23 15:49:56 EDT 2010
Revisiting this little problem - one of you suggested lubing the
oilite bushing at the back end of the speedo where the cable plugs in.
I tried that on the spare action I had on the bench, hooked up the
drive cable, and tested driving it with a variable speed drill, with
good results. That seemed to be the answer, so I tried applying it to
the "live" speedo in the car. Being the lazy doofus I am, rather than
pulling the cluster out of the dash where I could work on it sensibly,
I stuck the flexible hose from a bottle of turbine oil into the back
of the speedometer and gave it a good squirt. Since I couldn't see it,
I figured if one squirt is good, two are better, and I believe I
overdid it. The results are as follows: at low speed (less than 50 mph
by the tach) the speedo needle twitches off the rest and quivers in
the vicnity of 2-3 mph, and if I get to 50 or faster (by the tach), it
locks on an indicated 5 mph and stays there solidly until I slow down.
Here's my best guess: the speedometer action as far as I can tell is
pretty much like a galvanometer, with that little cup that rotates
against spring tension driven by the cable spinning a magnet, and I
have an idea that I managed to overload that cup with turbine oil so
that the rotational dynamics of the system are completely hosed up.
The good news is that the speedo no longer screeches, but obviously
it's useless as a speedometer. Does that analysis make sense? If so, I
can do either of two things,
1) pull the cluster and clean out the speedo cup, or
2) replace the speedo unit with my bench copy (which is actually the
one that came with the car originally).
I haven't tried either of these yet because it's just enough of a pain
to remove the cluster, I wanted to get a sanity check from VV first.
Please advise, and thanks in advance!
On Nov 4, 2009, at 8:44 AM, Charles McKinley wrote:
> The speedometer on my 63 Monza has had a problem ever since I got it
> in 1993, such that I've had to uncable it so that it doesn't work at
> all. Specifically, at speeds above about 40 mph, the drive cable
> screeches and the needle bounces between zero and the top peg.
> Before you suggest the obvious fixes, I've replaced the entire
> instrument cluster and tried several new drive cables (including a
> new cable housing), none of which helped. I have two speedometer
> movements, one in the car and one on the bench, and if I drive them
> externally (low-speed drill with a short cable), the movements work
> smoothly. I also discovered that if I loosen the collar on the end
> of the drive cable where it hooks up to the back of the speedometer
> unit, it works a little better, but still not as it should. This
> leads me to believe I might be missing some sort of a thrust washer
> between the end of the drive cable and the speedometer. Is there
> supposed to be such a thing? I don't have a complete shop manual
> that would show that level of detail. Or is it simply a case that
> the drive cable can't handle the ~270 degrees of twist between the
> trans and the speedometer without jamming somewhere? I've lubed the
> heck out of it numerous times to no avail.
> The only good side of this is that the Monza hasn't registered any
> miles in 15 years!
> Thanks for any advice,
> Chuck McKinley
More information about the VirtualVairs