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Speedometer Bounce

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Blueghost

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'78 Midget. 107,000 miles. Chasing other fairly loud (I'm about half deaf anyway) clicking/ticking/ noise that is only audible at slow speed - best heard when coasting to a stop - clutch and gear selection seems to have no effect - getting louder over last few weeks or I'm more sensitive to it. Noise isn't my real question.

Speedometer, Smith 0 to 120 mph; small number on face at 6 o'clock position - SN 5234/00 1000. Hard to believe they actually put a serial number on face, so guessing this is a "series number" or something for ID. Has always seemed fairly accurate. While chasing noise I noticed speedometer has more bounce than I recalled - maybe 10/15 mph bounce up to 35mph and less the faster you go - by 60 it is still there but only 1 to 3 mph. Thought noise might be speedo cable. Pulled speedo. Pulled cable. Found slightly lubed all the way - added white lithium grease - reinstalled. Drove (without gauge) and observed cable rotation - looks and feels (light finger resistance) steady at all speeds. Put drive lug into speedo and used drill motor. Hard to control drill speed at slow mph, but looks fairly steady.

Question - Is there anything that should be done with speedo BEFORE reinstalling? I can tell this will be a real joy as my hands just don't fit up there. Almost easier to pull steering column. Glass comes off easy. Looks like back shell holds internal guts w/ 2 screws. Is it worth while opening, blowing out, spraying w/ slicone or some other lube, or am I asking for trouble? Thanks, Blueghost.
 
Additional, I've already checked U-joints, Xmsm output shaft play, and differential input play. Also checked all wheel brgs. only real play is in drive shaft slip joint and don't know what is acceptable here. However, with it being multi-splined, wouldn't expect it to be the noise. I was first sure it was a u-joint getting worse. As I said in original post, noise isn't real question - it will be easier to find when it gets worse. Just care about spedo now. Thanks, Blueghost.
 
Here is my best guess, the transmission end of the speedo cable isn't fitting tightly in the gear any longer. You will need to get the car on stands, the speedo cable goes into the drivers side of the transmission. It is held in place by a fork shaped flange and one bolt. When you take off the flange, the gear just comes right out. With mine, I went to a train hobby shop and bought a piece of square (hollow) brass stock. I cut off a short piece and made it fit over the square end of the cable - reinstall is reverse, and, Bob's your uncle.
 
JP, You may well have the answer. Is the Xmsm end of cable supposed to be square? Mine is definitely not square. It is more like two parentheses together - () or football shaped. The smashed portion looks like it was uniformly squeezed for about 3/4". This may explain the bounce. I get from your post that it "should" be square.

Also, any input on disassembly/cleaning/lube of speedometer? Thanks, Blueghost.
 
It should be square - Nothing to say about the lube of the Speedo, except that the cable looks to be $25 on Moss - and for $25 try that first and see if it solves the problem. Pulling the Speedo apart is likely unnecessary - and certain to cause pain. :smile:
 
The inner cable should slide out from the speedometer end. Its easy to inspect and lube once you get it out. I've bought new cables that were harder to turn than the old crusty one so I always try to save the original unless its too far gone.

Kurt
 
Bringing back an old thread.

I had Baby Blue out for a very long ride today -- nearly 90 miles non-stop, with much of it at highway speed. After about 30 miles of driving at 60+ mph, the speedometer began making HUGE vacillations between 40 to 80 mph. It's pretty obvious the cable needs some serious lubing. Do you need to disconnect the cable from the transmission end to lube it up?

I peeked under the hood and followed the cable to where it disappears down near the firewall. Fortunately, I have a spare tranny so I can see where the cable hooks in. It still looks like a pain in the butt to get to. Is that a fair statement?
 
With the AH100-4 I had it turned out to be due to chaffing of the speedometer cable (that I fixed by giving it a lube).
 
Last edited:
SaxMan said:
Bringing back an old thread.

I had Baby Blue out for a very long ride today -- nearly 90 miles non-stop, with much of it at highway speed. After about 30 miles of driving at 60+ mph, the speedometer began making HUGE vacillations between 40 to 80 mph. It's pretty obvious the cable needs some serious lubing. Do you need to disconnect the cable from the transmission end to lube it up?

I peeked under the hood and followed the cable to where it disappears down near the firewall. Fortunately, I have a spare tranny so I can see where the cable hooks in. It still looks like a pain in the butt to get to. Is that a fair statement?
Click to expand...

Yes it is a fair statement. Before you going ripping everything apart, check that there are no tight bends or kinks in the cable route. And, i will not rummage under the dash on mine any longer without taking out the seat. Four bolts removed makes life so much easier.
 
If the inner cable is intact it should just pull out without any great difficulty from the speedo end. When you slide it back in you may have to do a little josling to get the square lined up. Hope a lube job does it for you. Often by the time it affects your speedo readings other damage has occurred.

Kurt.
 
I've seen the same thing, took the speedo out and spun it with a drill and saw the same behavior. The speedo mechanism needed a little lube. I know some guys a religious about this, but I took a chance on cleaning and lubing the speedo guts my self and it came out fine.

While you have it out you can tweak the calibration if you have something of known speed to drive it, or even better if you an optical tach ($30 at harbor freight).
 
The low mileage speedo off of my white Midget [30K] has a major bounce to it. I took it apart and inspected it for any problem but couldn't find any. I've attributed it to the magnets being in only one position for over 30 years. I've got plenty of parts so i'm running another but I'm curious as to its problem. I'd like to have the car show its low mileage but since not much of it is stock anyway...

Kurt.
 
I did pull the cable tonight. I also pulled the driver's seat for the long overdue repair to the seat bladder. I had to move the radio box to get easier access to the cable. Slid the cable through the firewall and pulled the inner cable. It was intact, but very dry. I cleaned it, put a blob of grease in my hand and pulled the cable through. Also lubed up the instrument end with some light oil (I use ProGold -it's a chain lubricant for my bikes, but it has found a lot of non-bike applications in my house).

There's a turnscrew on the outside of the rear of the speedo. It kind of looked like something you'd attach a ground wire to. Is that anything important? If it's how you calibrate the speedo, then I probably screwed it up.
 
I put he cables in a 5 gallon pail with oil in the bottom and let them soak over night. That's after I clean them in solvent. Only screws that come to mind on mine are the ones that hold the speedo body to the housing.

Kurt.
 
I haven't had a chance to torture test the cable now that it's been regreased, but the results in my usual back road driving are very encouraging...just a little wiggle down at lower speeds, but then the needle steadies out.
 
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