Speedometer/odometer issue - frustrated

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68original

68original

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A little over a year ago I sent my 68 Barracuda 150 mph speedo out for repair because needle was bouncing all over the place, came back and installed. Needle still bounces a little, but manageable for a 50 year old mechanical POS gauge.

So tonight I take the 68 out for a cruise since I just changed 3rd member and needed to mix up the sure grip additive in the rear end. While I am out I figured I would do a quick check on the odometer accuracy. This speedo has the trip odometer also.

I changed the speedo gear in trans to match rear-end ratio as close as I could get. It's within 2 mph at 60. The odometer is reading half the mileage it should, so I am like, WTF!! I go 1 mile and the odometer changes .5 miles.

How can the odometer be that far off? Clicks through the tenths ok, doesn't stop anywhere, just way too slow. Any ideas? I am soooooo tired of taking the dash bezel out for lights not working, gauges not working, etc.
 
I hear ya!

New or fairly new cable?

Mine would bounce and click back and forth until I pulled the cluster for new gauges this past winter. I pulled the clips and removed the mileage rollers to lube it all. Hardest part was re-assembly to but it back to the miles it was, 28 something k. It is smooth and quiet now. I hate having to pull the cluster!

Sounds like the issue if the speedo will actually read the correct speed like mine did! I dropped gears 2 winters ago and going from 4.56 to 3.55 with a speedo pinion change helped as long as I drove it alot. But when I pulled the cluster this winter it was clear that the shaft the indicators are on needed addressing. After disassembly I dressed the shaft with fine emery paper the re-assembled using white lithium grease.
 
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The cable is brand new. When the speedo was done, I was told they had to use parts that were 67 style with the threads, so I sent the cable to the repair shop so they could put the threaded end on the speedo end of cable.
I may try disassembly and lube, as the speedometer isn't original to the car so mileage showing is irrelevant. Either that, or put a spare 120 mph speedo in and see what happens.
Sucks that I sent this to a shop that supposedly knew what they were doing , and I still have issues.
 
the odometer is gear driven but some of that is plastic. If I had to guess, going by details you provided, the tenths wheel is worn out. That one indirectly carries every other digit wheel. Historically, many of these spools died at max load point, roll over 99999 to 00000, or shortly thereafter. Much like the slant 6 tossing the #5 rod. Just nature of the mechanical beast. They all die eventually. Back to that tenths wheel...
The plastic teeth in its I.D. wear away, its bore becomes egg shaped, etc... Sad part, its physically different from all other digit wheels ( more than the color difference ), and not interchangeable. Speedo and odo are 2 separate instruments in the same house. They can operate without one another. The same cable drives both though so resistance in odo can feed back to the cable effecting speedo operation.
Only positive note... Once the speedo is on the workbench, swapping in another digit spool isn't so difficult. Wish I could be more helpful. Good luck with it.
 
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I am just curious as to how you are testing the odometer? meaning how are you driving 1 mile and knowing it is one mile? I only ask because now I want to test mine to see how accurate it is.

I too, sent in my speedometer to a rebuild shop, charged me $175 to basically cut out my housing and install it onto another working unit. My needle is still bouncy from 0 - 15, then it smoothes out. I have tried lubing the cable and it makes no difference. Sort of a downer.
 
Thanks Ben.
I just bench tested my 120 speedo, needle stays pretty constant so that one is going in. My drill will get speedo to read constant at 58 MPH, and that took about 63 seconds to turn a mile so that also seems accurate. It is showing just over 74k on odometer, so I have 26k left before rollover. That's a lifetime for the Formula S it's going into! It's the 68 style, so maybe I can find a trade on here for the cable swap.

One quick question on the tenths gear - is the tenths gear on the odometer the same as the tenths gear on the trip odometer?
Since the 120 is reading good I probably won't tear into it, just wondering for further and/or other members reference.

To answer gdizzle's question - I live in rural South Dakota where there are roads at every mile section so very easy. As suggested though, interstate markings work, speedometer on cell phone with distance traveled, etc. Various ways to check.

Thanks all.
 
68original said:
Thanks Ben.
One quick question on the tenths gear - is the tenths gear on the odometer the same as the tenths gear on the trip odometer?
Since the 120 is reading good I probably won't tear into it, just wondering for further and/or other members reference.
Thanks all.
Click to expand...
I'm sorry but my memory is not that good. I would have to go look at. Here's a tip... when this instrument is loose lay it on the table and it rests on the input shaft. If that sight pressure lifts the needle ( new wouldn't move the needle at all ) there is questionable wear there. More than 5 mph needle lift, I wont install it.
That shaft is about 1/4 O.D. and 1.5 inches long. This to make rigid but, pressures coming from the speedo cable do wear this bore. Best we can do is route the cable into the instrument as straight as possible, minimal left/right or lengthwise force, and hope for the best. Do clean that square cable drive hole so the cable doesn't push into old hardened contaminated grease.
 
I love my Speedhut GPS Speedo, took all that crap out. But if you still want something mechanical...

Speedometers GPS Speedometers.png
 
Thanks.
GPS will be my next step if/when my 120 speedo goes out, and also probably the four-in-one companion for the other gauges.
If it wasn't a numbers matching car I would've gone this route already, but trying to keep it original looking.
Can you post pics of your dash setup?
Would like to see how your gauge(s) look installed.
 
68original said:
Thanks.
GPS will be my next step if/when my 120 speedo goes out, and also probably the four-in-one companion for the other gauges.
If it wasn't a numbers matching car I would've gone this route already, but trying to keep it original looking.
Can you post pics of your dash setup?
Would like to see how your gauge(s) look installed.
Click to expand...

My setup isn't stock. This is my Duster...

20170507_142122.jpg


20170423_213737.jpg
 
I have a '67 Barracuda. For now I'm using a Speedhut GPS speedo / tach dual gauge. I will be redoing the stock gauges, Speedhut says they can duplicate my stock setup look with their technology gauges.

20160830_162559.jpg
 
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