Need 1956 speedo cluster rebuilding advice

[lts70]

I'm about to jump into a speedometer rebuild for a 1956 3100. I changed the speedometer cable that ran from the turbo 350 transmission and although the needle moves now, it is very erratic and has a fairly loud knocking noise from inside the cluster. I was hoping for advice from those who have encountered a problem similar to this. Or any other advice in shining one of these old clusters up. thhings to do or not to do.

I have rebuilt many 67 – 72 instrument clusters. But I have so many spares that when something doesn't work I just swap parts. Don't have the luxury here only one cluster to work with
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[Gator Alum]

Subscribed! I'm about to tear into mine. Along with Its70, would love any and all advice.
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[1project2many]

There are many, many things I'll do myself but I had no hesitation about sending the speedometer out. The speedo works with magnets on a disc that spin inside a drum. As the magnets are spun by the speedo cable they "pull" the drum causing it to turn. A very small clockspring attached to the drum resists the effects of the magnets. It's a balancing act and when calibrated properly the speedometer needle will register 60mph when the disc spins 1,000 times per minute. The calibration is so sensitive that you can have problems with changes in temperature as the viscosity of your lubricant changes. Additionally, replacements for damaged clocksprings, worn bushings, and bent shafts can be very difficult to locate outside the speedometer repair industry.

With that said, erratic needle operation on an old speedo is often caused by dry or "sticky" grease. Cleaning it out with a good cleaner is the first step to curing the problem. Once the old grease and accumulated dirt is removed the next step is to get the parts properly lubricated. I have a tube of "Darmex grease" which was once available through GM that is about the best lube I've found for speedometer heads and cables. It was actually called out by part number in some old service manuals and was the recommended lube for automatic front hubs used in the early to mid-80s. Ford specs a Darmex grease for their auto hubs as well... unsure if it's the same product though.

After the speedo is lubed you'll need to check calibration. 1000 rpm of the cable should be 60mph. You'll need to come up with a way to drive the speedo at 1000 rpm though. Calibration can be as simple as turning a screw or as tricky as loosening a pinch clamp and stretching the clockspring slightly. Of course you should check at several cable speeds in case the spring rate is not correct. It would suck to get a ticket because your speedo is off at 30 mph.

[Gator Alum]

1project2many-where did you end up sending your speedo off to? Do you mind sharing how much a refurb was?

[sqrlnts]

You could also tear into it yourself.....
Instructions here.

[oldcouple]

Mine was okay until it hit 50mph,then it was good +- 5 mph with the bounce. replaced the cable and housing and the sender in the trans that was missing a tooth. But never trusted it in school zones, so switched to aftermarket.

[1project2many]

I sent mine to united speedometer and instrument in CA. According to the receipt, it cost me $37 to have it lubed and calibrated in 1997.

[sweet70beast]

All of mine that used to bounce ended up needing the cable lubed. If your is like my 53 Sub then you would undo both ends of the speedo cable and pull the part that spins inside of it out, it only comes out one way usually on the cluster side. You could clean it and I use white lithium grease to lube it. I put a bunch of grease in my palm and slid the inner cable through the grease and spin it as I am pushing it back into the outer cable. This may or may not fix your problem but it is a good idea to do.

[lts70]

Are these the guys you used to calibrate your speedometer?

http://www.automd.com/shops/united-s...nt-inc_414616/
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[1project2many]

That might be the old address. They've moved. Here's the web page:
http://www.speedometershop.com/

[_Ogre]

it was $189 to have mine rebuilt, i bought a new one from brothers on sale for $99
it was nice to have the new speedo indicate zero miles to show the miles on my rebuilt truk

[1project2many]

It's not too hard to turn the odometer back but it looks nicer when none of the digits have that "I've been staring at the sun too long" look.