Mercedes Benz Model
(107) R107 - C107
280/300/350/380/420/450/500/560 SL's & SLC's
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Mercedes Benz Odometer Repair
Note: while this may
not be the same Mercedes model as yours, the procedures are relatively
Remove the hush panel
under the drivers side dash. There are 3 phillips screws on
the top and 2 plastic phillips
half turn locks, 1 on each lower side.
Reach under the dash
and gently pull the odometer cable an inch or 2 through the firewall.
give you a little more
room to get your hand behind the dash cluster when you loosen the
Also I like to push
on the dash cluster from behind to aid in removal.
This is much easier
than using the metal tools on the cluster which
can scratch the cluster
and tear the sealing gasket.
This is why you want
some slack on the speedo cable. The cluster can move forward
allowing you to get your hand behind.
Remove the oil supply to the gauge with a 10mm wrench.
Disconnect the speedo
cable and remove the clock connection, the seat belt and glow plug
connections, speedo electrical connection, and tach connection.
Disconnect the master
harness for the gauge cluster. It is usually quite tight so
just pull gently straight out, don't rock it side
to side. This is the whole harness for the cluster.
Take the cluster and
put on a clean towel in an area with good lighting. Then remove the 4 screws holding
the clock cluster.
Gently lift out the
clock cluster and set aside. Remove the 2 screws holding the
speedo to the cluster, but do not remove just yet.
Remove the 2 screws
holding the gauge cluster and the dimmer switch. If your dimmer
switch does not work, now would be a
great time to replace it.
Remove the speedo electrical
box. Then the 2 screws holding the rear of the speedo.
Gently lift the edge
of the gauge cluster closest to the speedo. Lift out the speedo
and pay close attention to the trip meter reset
arm, which is why we lifted up the gauge cluster. This makes
it much easier to get the speedo in and out of the cluster
without damaging the reset arm.
I like to leave the
speedo in the cluster for much of the work just because I can do
all the "rear" work without
it laying face down,
and possibly bending the speedo gauge needle. These 2 plastic
gears are a common place for failure
of the odo. They
will often strip. Inspect them carefully especially the gear
closest to the cable housing inlet.
These gears look just
fine. The brass gear that rides on the plastic gear can sometimes
slip on its shaft, so
gently test it with
your finger. The brass gear is ok also so there is one more
place to look for trouble.....
Ahhh we found the problem!
The pot metal gear that the screwdriver is pointing to should NOT
without the entire shaft
and numbers advancing. This gear in fact does "slip" on the
shaft, hence the numbers
will never advance.
This is the hardest of all the gears to replace, but will cost you
only your patience, some time
and some locktight.
Remove the speedo head set with these 2 small screws.
Lift straight up and
be careful to grab the vertical plastic gear and set aside.
Seen in next pic.
I recommend getting
some scotch tape and lay on the numbers so that they don't move.
Very gently remove the
pressed on collar that holds the numbers shaft. Actually
you can pry it off or just take some
needle nose pliers and pull. To reinstall just take your needle
nose pliers and slowly push back on.
It is not on with great force to begin with. Please make sure
when you reinstall that you leave
a little room so the shaft does not bind, ie some end play. With
the collar on slam tight it will prevent
the shaft from turning properly. I got a drill bit the same diameter as the shaft (7/64)
to slip in behind, as I was removing the shaft.
GO SLOW and
CAREFUL. Don't let the drill bit get too far behind the
shaft as you are removing, or the gears will get out of phase.
With the shaft removed
you can see the shinny spot where the pot metal gear was slipping
and spinning. Take a flat bladed screwdriver
and very hard rough up the area. This will give the gear something
to bite on.
This is by far the hardest
part! Putting the geared shaft back into the number set and
getting the pot metal gear back into position.
It took me about 1 hour to do it. There is very little clearance
and the shaft obviously must be out at the point
where is the gear is slid back in. This causes the other numbers
to move and often fall out. Don't loose focus.
It can be done but a steady hand is a must. Also the phase
gears you see next to the numbers riding on a
second shaft, must also line up in the grooves of the numbers.
I resorted to pulling
out the numbers and gave it a try on the towel. After you
do get all the gears in place then you must get a drop of locktite
on the gear without getting any of it on or between the other numbers.
If you do then they will be frozen.
Use a toothpick and
put a single drop on the shaft after all gears are on. The
locktite will wick inside the gear. But only do this after
all the assembly is in the speedo, not on the towel. The reason
is the shaft must be taken out again if done on the
towel. The 2nd pic shows me lightly separating the space between
the pot metal gear and speedo housing.
This space is where you must get 1 drop of locktite. Right
on the shaft where the pot metal gear rides.
The finished product
installed and working great!