1973 450SL interesting speedo/odometer behavior

[Keystoner16]

I am working on a 1973 450SL.
The original complaint was that the odometer was not working. I drove the car and confirmed that the speedo was functional, and the odometer was not.
Removed the instrument cluster from the vehicle and removed speedometer.
I then inspected the speedometer and did not find anything visually faulty.
Re assembled cluster and re installed in vehicle.
When removing cluster I noticed that the speedo cable was quite loose.
I tightened it firmly when the cluster was re installed.
After this the speedo was observed to be inoperative, however odometer was initially functional. ????
The odometer worked until it got to 9/10 of a mile then stopped working again. At this point speedo and odometer were both inoperative.


I have now removed the cluster again and separated the speedo.
The speedo is observed to be functional when spinning with a cable and drill on the work bench. Odometer inoperative.


Hoping someone will have some idea what idea as to what is causing this.


Thanks.

[Sugar Bear]

The odometer inop. would be bad gears, you can probably find them online and DIY.

The speedo inop intermittently may be the cable just wasn't seated well or the drive and driven gears at the transmission are wearing out. My guess is it was not seated completely. Whilst it is out of the car remove the cable from the housing, clean it, lube it LIGHTLY with white grease but DON'T lube the last 10" or so to prevent grease from going into the speedometer head.

Once it is back together and working well don't reset the trip odometer unless the car is completely stopped.

[Keystoner16]

Thanks.

It seems weird to me that the odometer worked for 9/10 of a mile with not speedo operation.

I thought one drove the other.

[tyl604]

Here is my thread; I replaced the odometer gears on my SD several years ago and have not had a problem since.

The thread has info on where to purchase the new gears and good bits of information about how to accomplish the task.

I do not think the odometer problem and speedometer problem are connected.

https://www.peachparts.com/shopforum/diesel-discussion/355932-odometer-stopped-working-1981-300sd-2.html

[Keystoner16]

Good stuff. Thank you.
I believe I have found the cause of the inoperative odometer.
It appears to be the pot metal gear that is slipping on the shaft. Will the speedometer apart, I was able to operate the brass gear with my finger. While doing this, I was able to watch the pot metal gear turn. The gear was catching the shaft enough to spin the 10ths up to 9 but when it tried to turn over the odometer to a mile, the gear started slipping.

The speedometer in the SL appears to be a slightly different configuration to the speedometer in the write. As seen here.


The pot metal gear is on the complete opposite side of the shaft from the brass gear.
It is unclear as to whether this will make repair easier or harder. I will be attempting to re affix the pot metal gear to the shaft using green loctite as in the write up.