Odo works but not speedo

[JCochrane]

Hey all, I think I know the answer - "take it apart carefully and look for something that looks wrong and fix it" but wanted to ask in case someone knows before I dig in, and in case somebody else has the same issue at some point and likewise... (I searched)

Background: I took the binnacle off & speedometer apart to fix the trip reset shaft. When I put it back together, the reset would only roll to like 333.3 each time (I don't recall offhand). I could stop the press partway through to get it to stop on zero-ish, but that's obviously not good enough, so I took it back apart and checked for what I'd misaligned, figured it out and put it back together. Reset shaft works great - resets back to 000.0.

Then I go to drive it home, and find I have no speedometer. Ok, I've been here before - I must not have reinstalled the angle drive cable correctly when I reinstalled the binnacle. Take it apart, make sure the shaft is centered in the sleeve, tighten it back down. Still no speedo, but I noticed the odometer was ticking up a bit. Hmm. No time to diagnose, didn't have much option but to drive home, ~76.5mi. The odometer continued to tick up, including the trip odometer, so I kept with traffic and know pretty well my speed per gear/tach, so no issues on the way home. On the exact route I took, it was ~75.4 mi, and the trip odo clocked ~72.1mi, so... not that far off I think (~4%). (though the first three numbers are in the middle between 0/1,7/8,2/3, so maybe something's still not adjusted, or that's just how it goes).


So it seems the odometer works fine, thus the cursed angle drive (not original, but decades old) seems fine, so I clearly just mucked something up in the speedometer itself.

Any ideas exactly what I should look at? Possible the needle just isn't pressed all the way on or something silly like that?

[willisit]

I had the same thing and in my case it was the spring was in bits... but since you've had yours apart, I guess you'll know the status there. I, too, had ode, just no speedo.

[JCochrane]

I had the same thing and in my case it was the spring was in bits... but since you've had yours apart, I guess you'll know the status there. I, too, had ode, just no speedo.

If the spring is in bits (or otherwise nonfunctional), does that mean I need to replace the whole thing, or is it possible to get a replacement spring or repair it somehow? I suspect the specific spring tension is important...

[Rich]

A busted spring is fatal to the speedo as you've discovered.

You're right, you'll need to either rebuild it or replace it.

Replace: DMC offers them, including resetting the odo on the reproduction speedometer they'll sell you. At the moment they're out of stock. You can press the link on their listing to get notified when they have some in inventory. You can try to find a used one out of salvage via this forum or eBay/FBMarketplace. You'd need to take it to a shop to get the odometer set.

Rebuild: Find a local speedometer shop - yes that's really a thing - or find a speedo shop online to see what they can do for you. Broken analog speedometers are becoming a thing of the past but there are still plenty of shops. I don't know about how anybody sources or repairs the spring.

[Timeless]

Rebuild: Find a local speedometer shop - yes that's really a thing - or find a speedo shop online to see what they can do for you. Broken analog speedometers are becoming a thing of the past but there are still plenty of shops. I don't know about how anybody sources or repairs the spring.

My local tech referred me to Atlanta Speedometer for some gauge work on my 911. I'm 100% satisfied and turn around time was fast.

https://atlantaspeedometer.com/