The Stovebolt Site Forums The Shop Area General Truck Talk speedometer crazy needle syndrome

Got a new speedo cable from chevy classics. I tested it with a drill by hooking up to the speedo head and spinning it at the trans end. If I put forward pressure on the drill it reads fine but when I slack off a little the needle jumps all over and makes lots of noise. When I hook up the cable to the trans and put it in gear (truck is up on stands) the needle won't stay put. It's like it just needs to go in a little farther but I've checked and it's appears to be in the head as far as it can go. any thoughts?

It sounds like ye be in need of a speedo rebuild.

Make sure the cable drive has the correct end at the speedo. Should be the end that has the retainer so that the only way to remove the cable drive is from the speedo end. A small amount of white grease on the speedo nipple may also help.

Also check that the cable is in good shape and lubed

i have this issue with two speedo's cables. one that is a vinyal and the other one is a steel cable both came from jim carter. what i found is when i chuck up the drill with my spare speedo mounted in the vice i found i cant have the nut on the back of speedo tight because if it is the drill cant spin it over. when i loosen the nut a little it sometimes work and sometimes it jumps around. it does that with both cables. the vinyal one that is hooked up in the dump truck is the same way and i have to find a sweet spot in the tightness of the nut in order to get it to respond properly too tight its herky jerky too loose it binds it fast somewhere on the dial.

i hooked up a gmc speedo adapter (thier two speed rears) to the speedo in the vise and had excellant results with the steel cable and no herky jerky out of the needle because the key from the adapter is held true with the back of the speedo i dont know but i think what was happening on the back of the speedo is now happening on the back of the adapter but because of its configuration it didnt affect the speedo response it was nice and smooth. i went to put the adapter on the dump speedo and there isnt enough clearence to spin it on with out a conflict.

while i was experimenting on both cables and the speedo in the truck and at the vise with the same results i started looking at the cables. what i found is that i could not tighten the nuts completely without binding the cable fast. when i loosened the nuts the cable drops due to the weight of the cable and when i spin it it's enough to bind the cable which makes the needle herky jerky and can and does bind the needle in a fixed position until i straighten out the cable on the back of the speedo.

i had to look deeper as to why this was happening because i paid for two cables that dont work and the steel one is 3" too short which the speedo adapter is 3" long which makes that up. i had a messed up original cable that is no good but it has the right end on it. i laid all the cables next to each other and pulled all the cables out far enough to see how the connections were made. the old cable has a key and a collar with a washer between the collar and the inside of the nut. both new cables are the same except there is no back up washer between the collar and the nut. both were made on the other side of the pond and I think it is in the manufacturing of the cable ends themselves.

i contacted bob's speedometer and was going to get one from them he said it was $110 and i said that was a bit much but he said but we make them up special and they are made in the USA not overseas. i told him thanks but i couldnt see laying that kind of money out that only see occasional use. so im back to square 1

...Forty9 is dead on the money. Here is MY tale. I had my guages in my 37 rebuilt by D&M Restorations and they were really nice.
After some time the speedometer needle started doing just what neswes says his is doing.

I took it back..he hooked it up and it ran just fine. Back to the truck...same problem. NEXT I bought a NEW cable from the local parts house and put it in. SAME PROBLEM.

Took the speedo and cable with me back to D&M. Mike took one look at my cable and said "there's your problem". The OLD speedo end was worn to much, PLUS the speedo had a little wear in it.

Mike told me that with a little wear on the speedo itself and with the NEW cables NOT being as BIG on the ends make for double trouble. He then showed me a SPOOL of speedometer cable and you could see the difference with the naked eye. He made me up a new cable and my speedo has been as smooth as silk ever since.

I will also agree a little lubricant will help sometimes but it will not likely solve all the problem.
Hope this helps someone in someway.

thanks for all the advice guys. I will look at it closer but I don't really know what to do about the end of the cable that goes in the speedo head, I mean it is brand new so it isn't worn down or anything.If it is just slightly too small or loose in the head I really don't know how to fix that. If I can figure out a way to get it to stay in just a hair farther I think it might be OK. As I said in my first post when I spin it with the drill I can get it to work fine if I apply just a little forward pressure on the cable with the drill.

Try smacking/squishing the square part with a hammer to spread 2 sides out a bit. If you have a caliper .010"-.015" out of square may do it.

thanks curt I'm ready to hit something with a hammer! might as well be the end of the cable.

yeah my steel cable is brand new also and does the same thing. both ends of mine are plastic and molded on to the steel cable.