Odometer/speedometer issue

[akessel56@gmail.com]

<sub>I recently had to replace the engine in my ‘71 280 SL with a remanufactured engine. All is good but now the odometer will not register and the speedometer is a bit jumpy up to 40 mph. Cit was fine before changing engines.

Any thoughts what it could be?

Thanks.</sub> 

[Jonny B]

How long was the engine out? If for a while you would want to try adding a bit of lubricant to the cable.

I think the tach might be of more concern. That is engaged by the oil pump gear and could signal an issue.

Try the search function to  learn more about the tach.

[akessel56@gmail.com]

That sounds like something to try.
The tachometer is fine.

[Jonny B]

Oops sorry about that, my reading skills were not up to speed yet...

[akessel56@gmail.com]

I know first things first, but if the lubricant doesn’t work - and noting that the new engine was not identical to the old one.  I bought the car used in 1988, and when I checked the engine number when trying to decide to rebuild same engine or just have them send me a rebuilt one, found the engine wasn’t original - is there something else to check while my mechanic is looking at your suggestion if need be.

thanks again, Andy

[MikeSimon]

I don't see why an engine exchange will have to do anything with the performance of the speedometer?? There is no connection between the two, really. Unless the mechanics who worked on the installation messed up something else.

[Cees Klumper]

It is possible that the speedo cable was not properly connected when the rebuilt engine was installed. Check the connection, it's somewhere at the transmission as I recall.

[akessel56@gmail.com]

Do everyone, While speedometer is a little jumpy at lower speeds, the odometer is the issue.
My understanding is that the odometer, works off the speedometer, and if it isn't registering, the problem is in the Speedometer itself and not the cable.
Correct?

It seems that this is just a coincidence that the engine was being replaced, and the car sat for many months, but besides removing the engine from the transmission they didn't touch that cable.

At least the engine seems to be good!

Reminder its a '71 280 SL

Any comments?

[Pinder]

not sure if your car is a stick shift or auto. Mine is a stick and the speedo connects to the gearbox and at the gearbox there is a locking nut that if it comes loose  a bit it will show a jumpy speedo needle and it will also not show the correct speed.  On mine I tightend that nut. it is locked in place with tabs but they come loose.

[akessel56@gmail.com]

Mine is an auto, connects at the Transmission.
It's less about the speedometer that concerns me, I'd like the odometer to work.
I'm planning on selling it soon, and I will of course disclose. 
It just stopped working, after sitting for six months.

I had the same problem and had it fixed around 8 years and 3000 miles ago,

Just seems a short time to have an issue again.  But I thought it was replacing the engine originally.

Andy

[MikeSimon]

The odometer drive is a finicky mechanism with small gears engaging in notches in the number wheels at a certain point, so the next wheel advances by one digit. The most common failure is on the axle shaft the wheels sit on. They can develop slight axial play and the gears do not engage anymore. Another failure cause can be the reset mechanism, which will prevent proper advancement.
If problem persists, the only remedy is having it addressed by a professional instrument service.

[akessel56@gmail.com]

That is what I am afraid of.  I've had the thing fixed twice in the last 35 years, most recently in 2014.  Just kind of bugs me!

Andy

[Benz Dr.]

As I remember it, the odometer is on a separate shaft and the drive gear will go loose over time. Common problem.