1970 C10 Speedo Cable Replacement

[rmawyer]

Speedometer needle skipping. Truck has a 68 inch cable that goes from speedometer to a coupler (maybe for cruise control?) in engine bay. There is a second lower cable from same coupler to transmission that is about 55 inches long. Home mechanic friend used drill to show upper cable working; subsequently determined lower cable is broken, needs replacement. Not having any luck on tracking down a replacement cable. I may not be using the correct cable name in my online searches. Any ideas on where to look? Also, is the cable unique because of the cruise control? As always, thanks for any insight shared.

[ncpetersc]

https://www.summitracing.com/parts/o...del/c10-pickup

Maybe?

Don't know what engine/tranny you have, but the length of this matches what you are looking for.

[rmawyer]

Thanks for the information and confirmation, since it matches one I was finally able to locate on the JEGS site. I still don't know if the cruise control matters, but I took a chance and ordered the part anyway.

[ncpetersc]

Originally Posted by rmawyer

Thanks for the information and confirmation, since it matches one I was finally able to locate on the JEGS site. I still don't know if the cruise control matters, but I took a chance and ordered the part anyway.

I think cruise/no cruise may just change the length.

[rmawyer]

Thanks for responding!

[rmawyer]

I replaced the lower speedometer cable and still have same symptoms: needle skipping, sometimes stays at 0 MPH, never goes higher than 20 or 30 MPH. I've been told there are 4 major parts involved - the speedometer, the upper cable from the speedometer cable to an engine bay coupler, the lower cable from the engine bay coupler to the transmission, and a plastic (?)gear in the transmission. Since I replaced the lower cable with no improvement, and I have a replacement upper cable, should I try that next? Again, thanks for any advice.

[LockDoc]

Originally Posted by rmawyer

I replaced the lower speedometer cable and still have same symptoms: needle skipping, sometimes stays at 0 MPH, never goes higher than 20 or 30 MPH. I've been told there are 4 major parts involved - the speedometer, the upper cable from the speedometer cable to an engine bay coupler, the lower cable from the engine bay coupler to the transmission, and a plastic (?)gear in the transmission. Since I replaced the lower cable with no improvement, and I have a replacement upper cable, should I try that next? Again, thanks for any advice.

If you don't have cruise I would have replaced the two with a one piece cable. Did you lube the upper cable? You might try that, just pull the upper cable out, wash it down with solvent and lube it with a little light oil.....

LockDoc

[rmawyer]

Thanks. The truck does have cruise control. Is that the purpose of the upper and lower cable coupler in the engine bay? I was told I don't have to lube the cable but I can try that and see if it makes a difference.

[LockDoc]

Originally Posted by rmawyer

Thanks. The truck does have cruise control. Is that the purpose of the upper and lower cable coupler in the engine bay? I was told I don't have to lube the cable but I can try that and see if it makes a difference.

I don't know a lot about the cruise but if it has it I would leave the two piece cable....

LockDoc

[rmawyer]

I removed the cruise control transducer since it was disconnected electronically. I was then able to run only one speedometer cable directly from the speedometer to the transmission. The good news is the speedometer is now working. The bad news is it is now registering about twice the MPH (60 for 30, 100 for 50). Since the speedometer seems to be working, do I now need to focus on the gear inside the transmission? Thanks for any assistance.

[LockDoc]

Originally Posted by rmawyer

I removed the cruise control transducer since it was disconnected electronically. I was then able to run only one speedometer cable directly from the speedometer to the transmission. The good news is the speedometer is now working. The bad news is it is now registering about twice the MPH (60 for 30, 100 for 50). Since the speedometer seems to be working, do I now need to focus on the gear inside the transmission? Thanks for any assistance.

You may be correct on the transmission gear. That is a lot of difference. I wonder if one of these would help you....

http://67-72chevytrucks.com/vboard/s...d.php?t=758806

I don't really know for sure, but just throwing out suggestions.

LockDoc

[rmawyer]

Here's the latest. Took truck to a mechanic. He said the coupler / transducer needed to be repaired or replaced, since one of the receptors for a cable had become rounded. Even though I'm not hooking up the cruise control for now, I found a transducer replacement. Now I'm going to connect the two cables to the transducer. Here's my challenge - trying to find a GM cable roughly 36 inches long for the speedometer to transducer without having to make a custom cable. Anyone know where I can get one? No problem getting the lower cable. If this does not fix the speedometer issue I'll next replace the transmission drive, driven, and speedo gears. Thanks.

[demian5]

Originally Posted by rmawyer

Here's the latest. Took truck to a mechanic. He said the coupler / transducer needed to be repaired or replaced, since one of the receptors for a cable had become rounded.

Why not put a small amount of some tin foil on the end of the cable and shove it in and see if it works?

[rmawyer]

Thanks for the suggestion.