Slightly different broken odometer...
 

I have a 1970 911 and the odo broke in a new way...It rolled over from 39,999 to 39,000 and I fear it'll do it again. It has worked flawlessly for the last 3,000 miles, and continues to count miles (trip odo too), but now it's 1,000 miles off, and I suspect will get worse each thousand.

So. I've replaced that notorious gear before on an 80s car, but I've never had to mess with the cluster of numbers. Has anyone done this themselves? What am I in for? Last time the hard part was simply opening and closing up the speedo without damaging anything, but this time I fear what will be involved with the internals.

North Hollywood Speedometer wants about $400 to repair it, so Im inclined to at least investigate how involved this will be once I get it open...

https://youtu.be/pvm23fMcSEA
this vid helped give me confidence to fiddle around with the everything inside the speedo. i think i was more nervous about opening and ruining the bezels and bending the actual needle; but it wasnt as wild as i expected

That video is handy!

West Valley Speedometer quoted me $250, and I'm still waiting on Palo Alto Speedometer and Overseas Speedometer to get back to me, but that's a bit easier to swallow.

While I'm monkeying around, I might as well surface some useful info on this topic...Good info on DIY repair here:

http://forums.pelicanparts.com/porsche-911-technical-forum/196987-odometer-gear-replacement-electronic-speedometers-long.html

Some better shots of the numbers gears here:

http://forums.pelicanparts.com/porsche-911-technical-forum/1064442-odometer-gear-question.html

That's a great video for an electronic speedometer, but doesn't really help with the mechanical ones.

I've repaired a lot of speedometers/odometers and have never come across the issue you're seeing. Typically, with the mechanical speedometers it's the pot-metal gear that comes loose causing the odometer to stop working. In your case, my guess would be that you have either a broken number wheel (100's or 1000's position) or a broken little advance wheel between those 2 number wheels.

The mechanical speedos are a little more difficult to work on than the electronic ones. At least in my experience. They don't have the mechanical stops that allow you to twist the needle to losen it like the electronic ones. I have a process to disassemble them but it's more than I can type in a post. I'd be happy to help via email if you'd like. I also have a bunch of spare parts if you find something broken.

Or, if you want, I'll fix it for you. Probably $150-$175. I don't charge anything for the parts since I have a pile of speedos I use for parts.

I might take you up on that!

Another video of an earlier ('74) gauge:

https://www.youtube.com/watch?v=2OOFdHvFKbI&ab_channel=MTDesign

That's a good video as well. It's not brain surgery to fix these things. He did his repair without removing the needle and face. I've found it hard to work on these that way, but it looks like it's certainly possible.

Take a shot at it... I bet you can get it fixed. Happy to help if I can and if you find something broken just let me know and I'll find a replacement for you.

I'm in Anaheim.. Cheers

SmileWavy John did an awesome job fixing up my mechanical speedo trip and main odometer