Speedo repair....

[mrvette]

No I didn't fart in my shorts......


BUT driving the '72 vette yesterday, on the freeway where I could not pull over, the stupid speedometer started raising hell, squeeling, and finally the needle went all the way around to the 6 oclock position and broke off.....

needle is in the housing, I assume....finally managed to get the damn thing unplugged from the trans.....

anyone any concept as to where to get parts for this???

[StaticCling]

Buy the cable from one of the Corvette parts houses, I believe I got mine from Paragon or Wilcox. Manual trans cars are one piece, autos are two piece. As far as repairing the speedo, I would send it to someone for overhaul, it's a few hundred bucks to get it done.

[Mike Mercury]

if it failed to the extent that the needle detached, you will need to send it to a speedometer repair shop; and replace the cable as mentioned above.

[mrvette]

HOW in hell can the cable cause the speedo to fail....if the cable fails, it snaps...NO??? and if not the readings can be erratic.....I would think, but enough to push the speedo into self destruction??? so that to lube the cable with....??? ASSuming there is anything left of the speedo to work with, like find the pointer and glue it back together.....

why the loud squeeling outta the speedo up top?? this was most obvious....

not been on the freeways for months now....and of course it had to get cold before I went......can't win.....

Lets ASSume I can get it fixed.....BUT I finally located a speedo place to be able to convert it to electronics.....supposedly same face....interesting....

but 250 bux.....

[MrPeabody]

No thanks to the OP for that brief flash of an image of him in a speedo that went through my mind. Thankfully, in a millisecond my brain realized this was a car forum and it mean speedometer.

[Mike Mercury]

Originally Posted by mrvette

Lets ASSume I can get it fixed.....BUT I finally located a speedo place to be able to convert it to electronics.....supposedly same face....interesting....

but 250 bux.....

I worked for a company that repaired speedometers, tachometers, and cruise controls... many - many years ago

Lets talk tachometers for the moment. At one time (many years later) I offered conversion of 1968-1974 Corvette mechanical tachs to electronic... using the same dial face and pointer. This side business started about 2000; but I no longer do it.

A C3 owner could just simply purchase a 1975 or newer tachometer... they were already electronic by then. So why send their tach to someone who converts them for $$$? Because I maintained the fading of the tachs surface by reusing the mechanical tachs dialface and pointer; and it didn't look any different than the same & faded speedometer sitting next to it. I was doing about 2 per month; and providing a wiring harness and tach filter.

IF YOU CONVERT YOUR SPEEDO to electronic.... it will take more work than just swapping out the instrument itself, as you will need to provide 12vdc to the electronic speedo... and somehow connect the electronic instrument to a source of pulses that are ground speed related.

On the tachometers, the RPM pulses were easy to tap in to; it was one of the terminals on the ignition coil.

ALL THAT THIS MEANS IS... converting a mechanical speedometer over to electronic - involves a lot more work that you might be anticipating.

Be careful out there.

[Jeff '79]

Pics of Speedo

[JRD77VET]

Originally Posted by Jeff '79

Pics of Speedo

[VITE1]

Originally Posted by Jeff '79

Pics of Speedo

[StaticCling]

Originally Posted by mrvette

HOW in hell can the cable cause the speedo to fail....if the cable fails, it snaps...NO??? and if not the readings can be erratic.....I would think, but enough to push the speedo into self destruction??? so that to lube the cable with....??? ASSuming there is anything left of the speedo to work with, like find the pointer and glue it back together.....

why the loud squeeling outta the speedo up top?? this was most obvious....

not been on the freeways for months now....and of course it had to get cold before I went......can't win.....

Lets ASSume I can get it fixed.....BUT I finally located a speedo place to be able to convert it to electronics.....supposedly same face....interesting....

but 250 bux.....

You can buy a new Mechanical Speedometer from one of the parts houses for around the same price. Check out North Hollywood Speedometer, it's an outfit out here in SOCAL, but they are well known for quality work. They may be able to give you a better price, or just ask around on C3 Tech or General at the other place, a lot of good info over there...

As far as cable lube, I have been told by multiple sources to use Powdered Graphite or something similar.

Before I yanked my engine on the '73, my speedometer failed and according to a respected person 'over there' my speedo was in need of overall. I bought a new cable, and voila, it worked. However, I still don't have any trip odometer function etc. So it really does need to be worked on. But I have no desire to yank the dash on that thing right now, monumental task.

[Mike Mercury]

speedo/tach cables can squeal if they lose their lube. The inner rotating cable can also "twist"... throwing them out of round - and they will wreck the bearings in the speedo or tach in short time.

One funny part of offering tachometer updates was the NCRS car owners wanting the conversion. They always asked:

* can it be detected - that the tach has been changed & no longer mechanical?

* won't the judges see the tachs drive cable missing from the transmission ?

By using the old tachs dialface and needle, you couldn't tell from the cockpit that it had been converted. Well... I could but I knew what to look for.

As far as the tach drive cable, I told them to leave the outer casing in place; just pull out the rotating center cable from within the cable outer jacket... and reconnect the (now empty) casing to the transmission.

I learned that the NCRS judges got wind of this, and if a car was in the Top Flight category (which means they crawl under or use a lift) that the judges were instructed to unscrew the nut holding in the mechanical tach cables outer casing from the transmission... and verify that it did indeed have the center (rotating) cable part inside.

[mrvette]

Originally Posted by Mike Mercury

speedo/tach cables can squeal if they lose their lube. The inner rotating cable can also "twist"... throwing them out of round - and they will wreck the bearings in the speedo or tach in short time.

One funny part of offering tachometer updates was the NCRS car owners wanting the conversion. They always asked:

* can it be detected - that the tach has been changed & no longer mechanical?

* won't the judges see the tachs drive cable missing from the transmission ?

By using the old tachs dialface and needle, you couldn't tell from the cockpit that it had been converted. Well... I could but I knew what to look for.

As far as the tach drive cable, I told them to leave the outer casing in place; just pull out the rotating center cable from within the cable outer jacket... and reconnect the (now empty) casing to the transmission.

I learned that the NCRS judges got wind of this, and if a car was in the Top Flight category (which means they crawl under or use a lift) that the judges were instructed to unscrew the nut holding in the mechanical tach cables outer casing from the transmission... and verify that it did indeed have the center (rotating) cable part inside.

WITCH means there is nothing to prove the other end of the cable was not cut off.......unless of course they flipped it and watched the speedo....
interesting information anyway....

but I have contacted and OLD friend I not seen in 20 years....still in business....Tony's Corvette shop in Gaithersburg Md......doing some 150 cars a MONTH all of them Corvettes......so he gave me a lead on a guy who rebuilds these things BUT that guy is coming out with an electronic speedometer for maybe 250 bux.......by April or so this year....

I maybe get feeling better and weather break a bit, get out in the garage, pull that gauge outta there and see WTF....but then to put it back so to have the tach to tell me the speed.....

[markids77]

Gene... if it costs $300 to pay someone to pull the gauge cluster... DO IT!!!! If you have yet to navigate the morass of wires and fiber optics back there be warned; unless it all gets routed exactly and tucked in with care it WILL NOT FIT and YOU WILL NOT be able to reinstall it without breaking something. Aside from reinstalling the driveshaft on my 77 (no lift and on ramps so unable to rotate things), doing the gauge cluster made me want to throw sh!t more than anything else in the build.

[m and t's77]

Originally Posted by markids77

Gene... if it costs $300 to pay someone to pull the gauge cluster... DO IT!!!! If you have yet to navigate the morass of wires and fiber optics back there be warned; unless it all gets routed exactly and tucked in with care it WILL NOT FIT and YOU WILL NOT be able to reinstall it without breaking something. Aside from reinstalling the driveshaft on my 77 (no lift and on ramps so unable to rotate things), doing the gauge cluster made me want to throw sh!t more than anything else in the build.

So glad someone changed over my interior to a '78 style.

[mrvette]

Guys, I have had that dash cluster in/out of there so many times, I finally cut off all the gray wires, tied them together and ran a wire to a molex plug along with all the rest of the color lighting wires, so all that crap is eliminated via one plug now, and just one ground plug to the frames as they are tied together now, plus the tach plug in back since it's electronic now....has been for ~21 years now.....BTW the lights are all green LED now with the white faces it looks GOOD at night....The only thing is the tach is a smooth face, while that old face on the speedo is raised numbers, so the plastic overlay shows them through of course, but it's not really noticed unless you look for it, just bugs me....I dunno if later faces are flat and more in tune for the overlay or not.....I going to wait for the electronic conversion, trick is how many pulses per rev is the sender need to give?? I THINK the one that sends the computer signal is 4 pulses per cable revolution.....so at 60 mph that is 4000 pulses.....I was told that at 60 mph the industry standard was 1000 rpm on the cable.....

[Dave]

Originally Posted by mrvette

No I didn't fart in my shorts......


BUT driving the '72 vette yesterday, on the freeway where I could not pull over, the stupid speedometer started raising hell, squeeling, and finally the needle went all the way around to the 6 oclock position and broke off.....

needle is in the housing, I assume....finally managed to get the damn thing unplugged from the trans.....

anyone any concept as to where to get parts for this???

The bold might be your problem. It's not supposed to do that.

This place is near me. Haven't dealt with them personally, but I understand they do spectacular work: Welcome to Bob's Speedometer