1973 Cadillac Coupe Deville, Speedo works, odometer does not

[Kevin29972]

need advice on what to do with my instrument cluster, the speedometer works as intended, but the odometer has stop working.

[Dan LeBlanc]

It is likely the worm gear that drives the speedometer that has stripped.

Usually one of two things . . . old cruddy lubricant in the odometer drive, or trying to reset the trip odometer while the car is in motion.

Cluster has to come out, be disassembled, gear replaced, and re-installed.

I used Southern Electronics to recalibrate my speedometer in the 70.  All the other shops wanted to do a full restoration including cosmetics to the tune of $350+.  My speedometer looked and functioned fine but the reading was off.  These guys were $95.00 including prepaid shipping both ways and it works fine.  They were the only ones that would fix just the problem (exactly what I wanted).

www.instrumentclusters.com

[Kevin29972]

Thanks Dan, for the quick reply, I looked at their web site and it looks good. I will call them in the next few days as I work to remove the complete panel. Seems you are correct as I suspected something was stuck or stripped, I am already reviewing my shop manual instructions for removal!

[Kevin29972]

Update to my Speedometer repair,.
I spent one afternoon working to remove the instrument panel assembly, first removing right side a/c vent panel with clock, then glove box screws, then screws over instrument panel cover all to remove just the top cover. The the Auto temp sensor is removed, both dash speaker wires were soldered (had to cut them) to remove the top dash cover. next the lower panel on drivers side is removed , then the radio, and left side a/c duct is moved out of the way. Next are two screws on the back side of the instrument panel (difficult to get to) are removed, and last the Speedo cable and the wire Harness to the panel. Now the task of carefully maneuvering the panel to the right and up and out (finally) from the dash. UGH!!
i then researched who to send it to, and narrowed down to Bob's Speedometer, or Southern Instruments and after much review by me I decided on Southern Instruments. I had called and spoke to Eric (owner) and because they offered free shipping both ways , plus good reviews on yelp and the BBB off it went via UPS. it took then over two weeks to finally look at it, then the next day I got a call it was repaired. I was told that a metal disc fell off of the odometer gears, was re-attached and I am good to go for $95. They shipped it back and I installed it back to the car, test drove it and all was good. Except, Now I have a whirring, winding noise, up/down/up, and between 20 - 45 Mph. Now I did NOT have this before, just the odometer was not working. I am thinking it could be the cable. I have speed control so there are two cables(speedo cable to speed controller, then a cable to the trans.) Now , I am planning to remove the top dash cover and attempt to change the cable between the panel and speed controller. Meanwhile, I have calls in to Southern Instruments, have texted Erics Cell phone, all to No Replies so far. Such is Life!! Any suggestions you all may have are welcome!! Thanks for your ear!

[bcroe]

Likely the sound is related to the cables, which were disturbed in
the repair process. 

if the speedometer and odometer are in agreement, calibration
involves changing the transmission speedo drive gears, not
the head.  Bruce Roe

[Kevin29972]

Thanks Bruce for the tip! I have both Speedometer Cables new from RockAuto, and am intending to change the shorter one to the speedometer panel as I mentioned. As for the transmission cable, I would like to change that also. Problem is I need to learn more about the calibration process and changing the speedo drive gears. I have a shop manual and will be checking it for details on the gears, can you add any specific info that would help me with this?
Thanks,
Kevin

[bcroe]

I have a shop manual and will be checking it for details on the gears, can you add any specific info that would help me with this?  Thanks,    Kevin 

You can pull the speedo gears while the trans is in the car; best to
get the rear of the car high to avoid losing a lot of trans fluid.  The
driven gear comes out the side; its necessary to pull the driveshaft
to change the driving gear. 

The manual might recommend certain gears, probably to read high. 
There are formulas for calculating the gears which will come close:
if you know all the numbers and make no error, it will be close.  If
you want to get it exactly right, use measured roads, GPS, or your
favored method to determine the percentage error. Check the gears
and calculate the ratio; multiply by the error (like, 1.06:1) to get
the ratio you really want.  Then find a pair of gears close to the
new ratio and install.  Another way is attach an external gearbox
with the desired ratio to make the correction.  My speedo is an
order of magnitude more accurate than stock.  Bruce Roe

[Kevin29972]

Ok thanks Bruce, time for me to get studying the manual to get ready to begin repairs! if I come up with more questions, i will get back to you for advice. Hope you don't mind! I have my caddy in my garage, just need to set aside a day to get started soon.
Kevin