The Odometer a Known Issues

Replace Odometer gears - The advantage of doing this repair as a preventative fix is you won’t have to fish around and find all the tiny gear fragments. This seems to be an age-related issue, eventually, every 964 & 993 owner will encounter it. Two of the plastic internal parts, a gear, and the larger pod it attaches to become brittle with age. An easy kitchen table project to do.

The gear sets are available at multiple online aftermarket Porsche suppliers or even eBay. Be aware there are slightly different gears & pods with different numbers of gear teeth depending on the market where your car was originally delivered.

For example, if your car is the USA-delivered 993 the gear set is for a 993 sold originally in the USA market. The other way to ensure you get the correct parts is to count the number of teeth on the original gear & pod and buy the replacement parts with the same number of teeth. Also, see “How to repair a broken odometer”  on p-car.com or similar tutorials such as this available on several other 993 enthusiast sites. 

The most challenging part is to release the bezel ring to remove the glass to gain access to the internals. It is not really difficult, but requires one to go slow and use some care bending the rear-facing bezel edge to get it loose as you move along its back edge with a small screwdriver. Even if the rear-facing part of the bezel exhibits creasing from removal, it doesn't show from the front upon reassembly and doesn't affect the bezel's function going forward.

Broken teeth:

When removing the old broken gear/pod count the number of broken teeth and make a count of any loose teeth you find in the mechanism to make sure the numbers of missing teeth matches the number of loose teeth found so a missed tooth doesn't jam the mechanism after it is reassembled..

Other causes of an inoperative odometer/speedometer can be:

• The UAF2115 chip is not
  
  sending a signal to the stepping motor of the odometer. It can be replaced.
• Replacing the capacitors can resolve issues with a sticky speedo, the needle not moving smoothly or consistently.

Here is a video covering the process to replace  the above pod assembly:
https://youtu.be/71MKmTKATgo