The Stovebolt Site Forums The Shop Area General Truck Talk Speedo Cable Please help novice question

Hi,
The speedometer on my '58 long bed has started sweeping back and forth from 10 - 40 mph once I drive more than about 20 mph. A local repair shop seems to think the speedometer is the issue, not the cable and has advised me not to drive the truck to avoid additional damage. I need to use the truck for many urgent projects.
My question is this: Can I just disconnect the cable from the transmission under the truck, (I would zip tie plastic to cover the opening and the cable end) without causing any damage or leaking any fluids. Thank you very much for any advice - Al

A better alternative might be to disconnect at the back of the speedo. Tie wrap it up and have no worries about fluid leaking. Might also be a good time to check the cable is properly lubed.

Thanks Ed,
I tried reaching up under the dash and couldn't loosen the cable end in that confined space with all the electrical wire connections. I was also concerned about the "pin" within the cable spinning under the dash with all the wiring etc.. Disconnecting under the truck would be much more accessible if I wouldn't create other problems - Al

Mine is disconnected behind the dash. Once it was unhooked I was able to move it off to the side and tie it there so it wouldn't bother anything else.

It's not the speedometer ... it's your speedometer cable that's the problem.
I paid $60 for a new one. Get serious about disconnecting it from behind speedometer and it'll turn lose. Yes, it's awkward to get to but not impossible.
If you are concerned (I wouldn't be) about disconnecting it there and having a spinning cable behind the dash, just pull the cable out.
You're forced to disconnect the cable behind speedometer regardless. Might as well replace it.
Option number two is disconnect at transmission and pull cable out and reconnect the outer sheath. ... still need to disconnect it behind speedometer to replace it though.

If you're having trouble doing the required contortionist moves required to see the speedometer cable connection at the speedometer...do this. Find a board, I like one about 12" or so wide and about 4' long. Place one end of the board on the truck floor under the steering wheel, place the other end on a chair, saw horse or something else so it's level. Now you can comfortably lay on this temporary work platform and look and work under the dash.

Oh, now that you can easily see the back of the speedometer, do as suggested and just unhook the cable until you can buy a new one at Napa or from one of the many online vendors.

Good Luck,
RonR

Just disconnect it under the truck and cover the port on the transmission to keep it clean. Use your gps for a speedometer until you get it fixed.
After about 50 years the grease is dry as a bone inside the speedometer and the cable. Might need to disassemble to lube it up for it to work right again.
It doesn't take much drag to make the needle bounce like that, could be either or both. Its not going to hurt anything to disconnect it at the transmission, and the problem might cure itself when the weather is warmer.

I would disconnect The battery before doing anything under the dash.

The preferred disconnect is at the speedo housing. Someone in the past has tightened the fitting with a pair of pliers. You will have to use the same to get it loose. Once you get that first 1/2 turn the rest is finger tight. Do the job right while you are under there. Pull the inner cable out of the housing. Take some PB Blaster or similar and using the tube nozzle spray a good amount through the empty case. Then let it dry or blow it out with air. Go by your local FLAPS and get a tube of speedo lube. Lube the cable and slide it back in the housing then reconnect back to the speedo. One hour easy job and the problem is fixed for as long as you will own the truck. Good luck.

I agree with cold weather affecting those cables. I'm not saying that is the whole issue, but I've had them act up often in real cold weather.

Another alternative is to disconnect at the tranny, remove the inside drive cable and reconnect the housing. That prevents the speedo from turning and the tranny from leaking.

If the inside cable is dry and causing the problem. Remove it, clean and lube it with this stuff.
https://www.summitracing.com/parts/...D2sXV2AIV0I-zCh3_PgK8EAQYBCABEgL31fD_BwE

Thanks guys, all exactly what I needed to know (and excellent tips) to give me the confidence to get started, I did want to see if the cable could be the issue and not just take the word of the speedo repair shop. I did find the comments about the cold weather being an issue kind of funny, because I live in Arizona and this problem started at the end of summer when temps were in the 100s, It's 76 here today, you guys stay warm. Thanks again - Al