Speedo Works, Odo reads incorrect
 

1982 300sd

I am starting to wonder how this is possible.

The speedometer works and is accurate (verified by GPS)
The odometer reads off by a percentage of about 3 or so (60 mile trip reads 80 miles.

I do know that it is not the original instrument cluster, and there is the possibility of a transmission swap....but has anyone ever seen this kind of thing before?

-jim

Wondering the same thing, my '83 sd speedo is off .092 reads 9.2% fast
and the odo is off also, was thinking bigger tires but is there a calibration
to fine tune the speedo odo combo? using stock tire size

I've got the same problem with mine. My speedo is absolutely spot on (checked by GPS) but my speedometer reads 10% high. Mine is electronic (722.3x transmission) with the original cluster. I would have thought that the speedo and odo would be pretty linked. There is nothing strange with a different rear end, oversize tires or stuff like that.

So I'm hoping someone can explain what's going on.

By the way, if you're off 20 miles in 60 that's fully 33% high, not 3 high.

I'm betting you have a broken tooth in the odometer. These folks can help: Odometer Gears - Mercedes-Benz - 126 Chassis 79-91 Diesel

Speedo Works, Odo reads incorrect
 

My understanding is that the odometer gears begin to slip with age and at one point will fail completely. I know this is very common in the W123 cars and I would assume the W126 uses a similar odometer which will fail the same way. Do a search for diesel giant since there is a nice write up there for repairing the odometer.

But wouldn't slipping gears and missing teeth give a lower mile reading. Mine reads more miles than was driven...

I think slipping gears, or missing teeth would reduce the mileage indicated, not increase them...

sounds like something amiss with the cluster function.

I don't doubt that, but slipping exactly and precisely 10.0% for 15000 miles points to something else I would argue.

The 123 gears don`t fail, it is the Pot metal gear that slips on the shaft. easy fix.

The 126 gears as from what I have read, are made out of a different material and they break/crumble from age.


Checking the 240`s spedo against the GPS, and it registers slightly more miles from what the GPS indicates.

Checking the MPG, I like using the Spedo :D


Charlie

I get close to CraigsList numbers when I do mine that way. :D

Drove from Portland, Or to Lathrop Ca. GPS 618 miles, Spedo 628 miles, 10 mile difference.

80 240D, speed 55 - 60 all the way (hard to do) 38.74mpg vs 39.34mpg.
3:58 Diff and 150mph Spedo, w/4-spd.

Hello CL, this 240 gets 40mpg :D

Charlie

I had some of the teeth on a gear inside the cluster fail. I pulled one from the pick and pull and fixed it.