Anything other than the gear that would prevent odometer from working?
 

The odometer stopped working on my 150mph speedo. Swapped it out with the 85mph unit that I have. Same thing, odo does not work. Is there anything else that would cause this, or do I have 2 broken odo's?

There's a "stepper motor" in there that works it.

John, not sure I understand. There is a stepper motor in the speedo? If so I assume I have 2 broken odometers? Or is the stepper motor somewhere else in the car that is affecting both?
Thanks

In the speedo.

Could possibly be the speedo pulse sensor mounted on the side of the transmission that feed the pulses to the stepper motor, or the wires leading to the speedo itself. Could explain why both speedos don't work.

John, after re-reading your post I got what you were saying.
uwanna, is there a way to test the pulse sensor?
What would you do in my situation, send one out for repair assuming both are bad? I'm open to suggestions.

Follow the procedure in this post below. With a multimeter set to the ohms setting, test
between the two wires (disconnected) that come from the sensor puck and enter the body just below where the shifter shaft does. They run thru a small rubber tube, and have two connections you can disconnect. As you spin the right rear wheel by hand (jack it up)you should see the needle deflect as the reed switch in the sensor is opened and closed 8 times per revolution.

http://forums.pelicanparts.com/porsche-911-technical-forum/333215-1986-speedometer.html#post3134698

Thank you sir, been 24 degrees in the garage these past few day, 43 on Thursday, will try it out then.

If you're speedo is working then the sensor is fine. Sensor drives both speedo and odometer
As John said the stepper motor is probably bad

My apologies to the OP, misread his post as speedo not working, when in fact he said
odometer. the above statement is correct.

uwanna, I just read the link you attached and was going to ask about that. Yes the speedo is working on both, it's the odometers that don't work. I haven't taken them apart so either way it's the units themselves that need repair and not some sensor in the car I take it.
North Hollywood I guess is what's recommended here from what I've found, correct?

North Hollywood is fine, so is Palo Alto.
As long as you're sending it out I would ask them to calibrate the speedo, unless it has already been done. Stock speedo can read as much as 5% high

Your problem is most likely the dreaded crumbled plastic drive gear problem. If you are handy with tools and "fiddily" stuff, there's a somewhat detailed fix, but it can be done with much patience! You just take apart the speedo and replace the little plastic gear. If you feel like tackling it, you'll save yourself $100 or so. Here's a very good,detailed procedure.
PP sells the replacement gear, you'll need the 20x30 gear:
1980 Porsche 911 SC Coupe - Gauges & Miscellaneous - Page 3

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

I used Nichols speedometer and instrument (NSI) repair service in Greensboro NC. They are an authorized VDO repair shop. They repaired and calibrated mine for a reasonable price. A year later the odometer crapped out. Called NSI they asked me to return the speedo. John is correct, Stepper Motor was bad. NSI repaired it at cost ($80.00) no labor charge. Very pleased with their service and turnaround time. They don't do custom work like Palo Alto or north holiday, but they're on the East coast, closer to me.

Thanks Bob, I'm also on the east coast and North Hollywood has not responded to my e-mails. I'll give them a look.