Yeah you got that right. I bought my 240D with a stopped Odometer. My 300SD was in great shape with 150K on the clock when I bought her but I soon found out the odometer was slipping at high speeds. I got a good price on the car because I had a 3-4 flare on the trans. I got the car up to 200K before the trans gave up. But still, I would have paid less had I known it had 10-20% more miles as I estimated by GPS measurement vs. the readout.

The car actually looks better now. New Tex. Clean paint. New window rubber. It's actually shocking how many 123s and 126s on Craigslist have less than 200K after 35 years. They don't of course. Bad odometers on them all at one point or another. There's no way that any of these cars have made it this far on their first odometer. I've owned three of these things and everyone had goofy odometers.

And I took my car out on the highway today. I didn't have my GPS but I swear the odometer still slips a bit at speeds over 70. It's fine at 60. Goes one mile in a minute. But the odometer seems to slow down as I get over 70. That is, I should be doing 0.1 miles in less than six seconds but it takes ten seconds to do so. Like it still slips at high speeds. So I hay have another issue besides gears. My speedo reads correctly so it is hard to image what else is wrong.

Oh well, I will continue to investigate.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles

I opened my odometer up again. I took the car out on the highway and used a gps odometer app on my iphone to check my odometer. The speedometer is spot on but the odometer was up to 20% off. If I went over 75mph it would just stop. No tenths clicking off on the trip odometer.

First off, I opened up the speedometer again and looked inside. Here is the reset mechanism. When you push the reset button, the big shaft of little pinions that turns the number wheels pulls away from the number wheels. This clearly disengages the drive cogs from the number wheels and allows the number wheels to be set back to 000.0 using some little finger like mechanisms.

The odometer mechanism:


Closeup of the trip odometer drive:


The second steel shaft in the upper part of the image has the little drive pinions on it. If you press the reset button, this shaft swings down and the dogs of the gears disengage from the dogs on the digits before the numbers get set to 000.0.

This is why I think you cannot bust your gears while pushing the button while driving. The moving pinions on the shaft are disconnected from the digit wheels and rolling the digits over puts no load on the gear train.

However...there is always a but. If the car is moving the dogs are being loaded. They may bind together if there is load on the gears and not separate completely before the digits are zeroed. Just a theory. But, I suspect there is something to all the stories about losing the odometer while doing a reset while the car is moving.

Porsche people complain, MB people complain. So there is prolly something to all of it. Anyhow, just thought I'd share how the thing actually works.

The good news is I fixed my slip problem in my odometer I was seeing at high speeds. I'll post up a separate thread since it really isn't about odometer swaps.

Thread is here:
Fixed 1982 300SD odometer slip at high speed

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles
97 C280 147k miles