1971 Eldorado odometer - very strange

[Cadman-iac]

Yes, given its age, it's still very flexible. Even after all the heat and cool cycles it's been through.

[Cadman-iac]

Ok, sorry for the delay, I had to look at my odometer parts again. I have a rather large collection of parts from various vehicles that I have parted out or scrapped, but I only saved the rotating pieces, none of the housings, and that's making it difficult to describe how to put one together. I hadn't realized until today that depending on which vehicle you are looking at, the trip meter when it's reset can be wound forward or backwards. My Suburbans, both the 88 and the 90, wind the trip meter backwards from the normal rotation. But my 77 Sedan Deville winds it forward when you reset it.
So this makes it critical that you know which way the shaft sits in the housing, because if it's new enough to have the groove in it, it won't work correctly if you put it in backwards. It won't catch the spring rings that lock the number rolls when the shaft is rotated.
And it won't let the number rolls rotate while driving because they will catch the spring ring on the lip of the groove and lock the number roll to the shaft if the shaft is installed backwards.
So again,  it's critical that you know which way the shaft sits. Look at it before you remove the trip meter, and make a note of which edge of the groove is tapered and which one is squared.
  I've posted another picture of the shaft with the groove in it. Hopefully it's a good enough picture for you to see the details of the groove on the shaft.

[Cadman-iac]

So when you begin to assemble the odometer pieces, the first piece is the drive gear followed by an alignment segment, then the tenths number roll of course, followed by an alignment segment with the small gear. To make this as easy as possible, if you have the zero facing you, then the split tab on the alignment segment will be at the number 5 position, and the gear is at the number 7 position. The small gear will almost be engaged with the 2 teeth on the left side of the first number roll, and make sure that the side with the uneven height teeth is against the roll, or facing right.
The critical part of this is when you put the next number roll on. The right side of each number roll has teeth all the way around, and one tooth off will place it out of alignment by half a digit.
You will also have to keep each of the pieces from rotating while you are assembling it, or it's very easy to get one out of alignment, and then you will have to take it apart and realign the pieces again.

  There are small retainers, like a small brass washer, that are pressed or crimped on the shaft to keep the pieces in the proper place. These are removable if you are careful, and you will have to reuse them when you reassemble the odometer. I haven't found a good way to either get them off, or put them back that doesn't do a little bit of damage to them. They don't fit into a groove or slot, they're just a press fit. So if you should have to remove one, just be careful with it. I've found that if you grip it with a pair of needle nose pliers and turn it on the shaft, that it will usually come loose and slide off the shaft.
To reinstall it, the best way I can offer you that I have had luck with is to put a pair of vice grips on it when you get it in place and squeeze it gently to get it to stay there.
One other way I've tried with some success is to flatten the washer by hitting it lightly with a hammer so it narrows the hole, then I use a piece of 3/16" tubing about 3 or 4 inches long to drive the washer onto the shaft like a press fit of sorts. I don't know how the factory does it other than just a press fit. But this is all very difficult to do and keep everything in place at the same, so take your time, be careful. If you lay it down on something, be sure to protect the numbers from getting scratched. And don't try to clean the numbers off with anything but water. They are just printed on, and after years of being in the heat of a confined car, and baked by direct sunlight, they can be wiped right off in the worst of cases.


This first picture shows the drive gear and the retainer washer installed on the shaft.
The second one is a speedometer out of one of my trucks. You can see how the numbers are coming off after years in the desert sun. This is why I collect odometer pieces, to rebuild ones like this.

[Cadman-iac]

When you get all the pieces on the shaft and lined up, they should look like this picture. Once they are, you can check to see if they are in place correctly by trying to turn the left most number roll forward, like it's being rotated by the speedometer drive. It should be locked in place with all the other number rolls.
If you turn the right side this doesn't work. You can only check it with the left roll. The right roll will turn like it's supposed to.

[Cadman-iac]

  Once you have everything assembled, you can test it before you put it back in the car by using a drill to drive the speedometer with.  One of those "Robertson" screw drivers  with the square end on it fits perfectly into the speedometer.  It has the same shape as the speedometer cable end does. So run up a few miles and make sure that it rolls over the way it's supposed to,  and reset it to be sure that works as well.
I'm sorry I didn't get into more specifics on any one trip odometer, but there are so many different designs that it's impossible to describe them all. But the basics are the same, so hopefully this will help you make your repairs if you choose to try it.
If you have any questions, let me know and I'll try to answer them as best I can.

Rick

[79 Eldorado]

When I get the car out I'll take note of exactly what the trip OD is doing then I'll look back at this. As far as "fixing" since I never took any of the individual parts apart I suspect something might be worn. According to what you wrote I think I've got a better chance at screwing something up so it may stay the way it is.

Scott