The Stovebolt Site Forums The Shop Area General Truck Talk How Fast Was I Going Officer?

Here’s today’s question (I did try a search first, but didn’t find this same question): The speedo needle in my ’63 C20 waves constantly. That is, is works like a metronome, wavering in a perfect 10 mile per hour “range.” I believe my speed is the mid-point of the arc. For example, if I think I’m traveling at 50 mph, the needle waves between 45 and 55 mph on the dial. The wave doesn’t get faster or slower with the truck’s speed, nor does the length of the wave change with increases or decreases in actual speed. It is just a nice consistent wavering back and forth in a 10 mph range.

Since it is my daily driver again, I’d like to fix it when the weather warms up.

My questions are:
1) What might be going on?
2) Is this something I can fix? My mechanical skills are only OK. I can fix most things, but only with written instructions – I can’t just diagnose and fix stuff from memory. About the only way I tackle anything mechanical is if it is in my Haynes Manual.

Please type s l o w l y. I’m not too smart about much of anything related to the driveline.

Additional Info (Don't know if it matters): I'm running a 70s (Nova?) 305 Engine with the stock 4 on the floor.

Thanks guys!

I had the same problem on my 57, in my case a new cable fixed it. I'm sure it could be other things also.

I agree it'll prolly be the cable, but if that doesn't cure it, gummy guts in the speedo is the next possibility

Bill

Rather than replace it can you try putting some type of lube into it first to see if that frees it up?? I thought I'd read somewhere here about the best type of stuff to use.... WD-40 maybe??

My speedo doesn't work and recently, here in our small town when one of the cops stopped into the store it was "suggested" that I was going a little faster then I should have been the other day... I told them that I was pleased to know that my old bolt could go that fast!

As others have mentioned, try lubing the cable. Also, make sure the cable and its outer jacket aren't kinked or bent around a sharp corner somewhere. You can actually remove the cable jacket from the speedometer and from the transmission. Put the assembly on your bench and carefully slide the cable out of the jacket. Clean any gunk then relube it. Light oil, light grease. Whatever you prefer. I'd use a light grease.

does it get better after it is warmed up?

As stated, cable lube is usually the problem. When the lube gets stiff, the needle starts wagging the dog. If you were in the south, I would agree with soft grease. Instead, use speedometer cable lube, it contains a lot of graphite and doesn't get as stiff when it's cold. You can get it at an auto parts store.

You can remove the cable from the housing by disconnecting the housing at the tranny. Carefully grasp the end with pliers and pull. When you put it back in you need to turn it so the square drive will slip back into the speedometer head.

I usually go ahead and replace the cable and housing. Don't know if you can still buy the kit locally for your truck. They also sell a generic cable that you cut to fit and crimp on an end. Last one I bought had lube with the new cable.

Thanks for the help guys. This sounds do-able enough. Now I have an excuse to go parts shopping!

FredT - thanks for the specific instructions. That's exactly the kind of help I need!

Joker, it doesn't change after it warms up. I drove it to town and back twice today (about 30 miles each time). I did get it up to the 65+ mph range (I almost never drive that fast), and it seemed to have a little more "range" - about 12 mph swing each way when it was at highway speed.

You cannot pull the cable out of the housing from the trany end. You must pull it out at the speedo end. Grease it good & slip it back in. If that doesn,t cure it sometimes the cable is too long. You can trim a little off the trans end.

when mine is cold it will flop around, after it warms up,, it will show the correct speed,, serious,,no joking on this one...so I thought that might be the problem....Fred

Kim, I agree, sounds like you need to lube the cable.

After you get it loose at the speedo end it will slide out of the housing.

Wear some work gloves because that cable will be nasty with old black lube and it is very hard to get off your hands.

Hobert

"Did yo know you know you were speeding, Sir?"

"Yes, and so were you, Officer!"

I had the same problem. Lubricating the cable helped a lot - now it only happens when it's really cold, and only for the first km or so. I used white lithium grease.

Johannes

What ever you do don't use WD-40 to lube the cable it will attract every speck of dust and gum the cable up quickly. The WD stands for water displacement formula 40. A dry lube like graphite is the best. It is also not effected by the cold. Not that I worry too much here in So. Calif. but in N. Dakota it could be a problem. Best of luck.

One alternative: I haven't had a working speedo on my truck, ever. I have a tach and I rode with a GPS and marked down the RPMs for speed and have a plastic covered card hanging from the headlight knob with the speeds in gears. I can now do it by engine sound! Which is good because I burned up the tach! DOH! Fortunately I got another one waitin to go in. That is, if the weather every clears... :rolleyes:

If all the excellent advice above does not work, you might look at the speedometer gear/bushing assembly in the transmission. I had one do the errattic needle jump and just lived with it until it didn't move. The "fix" was a new speed-o gear in the transmission. It seems the little bushing in the speed-o gear was "egged" out and was only connecting on the "high" side.

You beat me to it 49, thats what happened to me. the gear just wore out and lost a couple of teeth. easy fix.

I have found a cleaned & well lubed OE cable is superior to the offshore one bought at your FLAPS. I pull them(cable & casing) soak in solvent, blow dry & use a blue teflon or white light bodied grease like lithuim. Also sewing machine oil on the 40 y/o speedo itself won't hurt,,my 2cents,,brian

Thanks for the tip 64fl. I had just decided that it might be easier to replace the cable instead of actually taking the time to clean it - I found one at Truck Shop for $11, so I thought it would be simpler to switch it out instead of cleaning up the one I have.

OK then, clean it up it will be. Hopefully, I can do that next weekend with Dad's supervision. Thanks guys, for all the advice.