vetteguy22

I have the original speedo in my 70 Vette but it has started to read high. Appears to be the speedo itself. I’m running a t56 magnum trani so I was wondering about going electric this time.
I want to keep it looking original.
I thought I remembered hearing about using a newer year electric speedo but not sure if that’s correct.
Any suggestions guy?
Thanks,
Rob

71VetteLover

I have heard electric speedometers are available for our C3's that look exactly like the OEM speedometers. Try calling Instrument Sales And Service and ask about them.

bazza77

all the speedo's in the c3 were cable driven,

it was the tacho that went from cable to electric .

This is the factory history , no doubt there is aftermarket things to get where you want .

So you Magnum has a cable drive on it now ?

vetteguy22

Yes the magnum trani has both the electric and cable set up available on it and I went with the cable since that’s what I had but now, three years later the speedo is reading much to high.
Used to be right on.
I’ve pulled the cable, checked and lubed it and checked the drive gear so figure it must be the speedometer itself.

maj75

I don’t think a cable drive speedometer can just start reading high. They are gear driven and the gears either work or they don’t.

vetteguy22

Ok I’m up for suggestions.
As I stated I’ve pulled the speedo cable and gear, checked and lubed them and it didn’t change anything.
I havent altered the car in any way in the last 3 years. Same tires, etc.
What else could it be?

bazza77

Did the problem start after you lubed it ? I ruined one on my 77 when I helpfully sprayed the internals with wd40 !!!! but it didn't just read high, the needle just started bouncing all over the place

Have you taken the cable off the back of the speedo head unit and checked to see if there's any oil from the gearbox in it ? I say this as I have heard of oil getting (pumped or wicked ) up a cable ? Sounds crazy I know

If your after originality and you have verified its not the cable or drive/driven gears . Then maybe the quickest fix is to get your unit overhauled or get another one that is known to be ok.

vetteguy22

I didn’t do anything before it started acting up. I pulled the cable and inspected only in an attempt to find the problem.
I didn’t check the back of the speedo but do know there was no trani fluid on the cable.
It reads high at all speeds but doesn’t bounce, it’s steady.

bazza77

Ok , I know the odometer and trip meter are gear driven as I changed one of the cog set up in a 69 ages ago . But I think the actual speed dial is not but I never went into it that far so I'm sorry I cant help any further with that .

Maybe get hold of Willcox ,or check his site out as they have lots of trouble shooting vids on there.

Apart from loosing the mileage read out , changing the whole unit isn't that bad a job.