sorry it is a 79

It's no big deal, but thank you for the info. I can answer this one. Your car does use a cable. Checking it is fairly simple, but can be a little frustrating for some people.

Usually, the cable insert is indeed the weak link. Frequently, one that is about to die will cause a jerking, unstable speedometer needle, as even a noise, frequently a clicking that increases with speed.

Honestly, the best way to check them is to slide them out of the sheath. but it's not always possible to do so easily. By pulling it out, a complete inspection can be made from tip to tip, and it's the only way to be sure there are no fraying strands or kinks anywhere.

On my 300D, I actually removed the cable from both the cluster and the transmission, removed the cable from the sheath, and cleaned both completely with brake cleaner before applying lube and reassembling them. (Preventative maintenance, and very possibly overkill.) At least now I know that it's in perfect working order.

I suspect there may be a thread or two on here with great instructions for accessing the cable from both ends, which is important should it be broken in the middle somewhere. My memory is a bit fuzzy, as I did it months ago, or I'd attempt to walk you through the process. I'll see if I can find a link or two.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

Here's a recent one with a good photo that shows roughly where the cable is located at beneath the car where it attaches to the transmission. Hopefully, yours doesn't look like this. Speedometer cable pic


Here's a concept. Looking at the cable to see if it turns while driving... Brilliantly simple. Maybe worth a try.
Easy question about 300D speedometer


Warning, it appears there may be more than one style of cable. I didn't know that until just now. speedometer and odometer inop


So, Maybe try out driving with the cable disconnected and seeing if it turns would be a good place to start. I've never tried it, so I can't say how difficult it is to watch the cable end and drive at the same time, but it seems like a decent, quick test.

__________________
- K.C.Adams

'77 300D Euro Delivery
OM617 turbo / 4-speed swap
404 Milanbraun Metallic / 134 Dattel MB-Tex

Current status:
* Undergoing body work

My '77 300D progress thread

If you do pull the instrument cluster you can stick a small screwdriver or square drive bit in the socket where the cable fits on the speedo. Turn counterclockwise and watch for the odometer to move. You can see the how the gears mesh and activate the odometer mechanism. It's not too hard to see if they are turning or not. If you have a speedo cable insert handy chuck it in your reversible drill and crank it up counter clockwise. Start slow and build speed just like in the real world.

sweet i was planning on taking it apart in the morning when the snow stops and it will be easier to keep things open i shall try driving it test and see if it helps out at all. if not i have to wait for a week to get the cable to replace it.

i pulled the speedo cable off from the reader and drove it like suggested didnt watch the cable as i was driving home but held on to the end to feel if it spun.
the cable itself still works to the best of my knowledge as it spun in accordance tpo my driving the car. the pin on the end that is removed is my question it looks like it may have broken at the top
the speedo does not move with a small screw driver in the hole the speedo came from

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