Steps to troubleshoot speedometer

challenger

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A few years ago my 1970 300 speedo was making noise and was jumpy. I did research and got a replacement cable What I got was longer than the original but I was able to get it to fit . Since then the speedo only worked sometimes. Can anyone help me with the steps in troubleshooting the speedometer .? I know what to do but figure the order of operation might be different than the way I'd do it thanks
 
Do you still have the old cable? Mopar used to sell a sort of waxy product designed specifically to lube speedo cables. It sounds like your original was dried out and binding up. The new cable, as it's longer than stock, may be binding up as well for other reasons.

I don't know what the product of choice is these days, the Mopar grease/wax isn't available anymore. But I'd start by greasing and reinstalling your old cable (if you still have it) and see what the results are.
 
White lithium grease is what I used on my '79 Dodge Magnum last year. But equally important is the comparison of the speedo cable. Mine upon close inspection found a small part of the tip of the cable going to the speedometer broke off. Thus, the replacement must be slightly longer to work properly. Also you did not mention if your car has cruise, if so does it have a cable going direct to the speedometer.
 
Troubleshooting? FIRST, make sure the odometer works. That's the direct connection to the transmission's geared cable drive. So if that works, it shortens the troubleshooting procedure a good bit, right off the bat.

If the odometer works, but the speedo needle doesn't work, then you'll need to remove the speedo head and get it to a speedo shop for further diagnosis/repair.

Keep us posted,
CBODY67
 
Thanks for the replies. Unfortunately I haven't been able to get back out to look further.
This car doesn't have cruise control btw.
If I may pose a few more questions in case anyone wishes to give me answers:
Is there a good OEM spec speedo cable for this car? 440 hp auto if that matters.
Can someone recommend a speedo rebuild shop?
If I try to spin the cable from the end that plugs into the back of the speedo should it spin or should the gear prevent it from spinning? Sorry if I already asked this. I can't "go back" and check without losing this post on my "smart" phone. The phone may be smart but me? Meh, not so much .
Would it be advisable to put a drill on the transmission end of the cable and spin it (clockwise???) to check the speedo head?
Many thanks again.
 
There are probably some replacement parts speedo cable assys out there. Internal cable and outer housing. I suspect they'll all be pretty much the same quality. Only thing is you'll need to know the length of your current housing. HOPEFULLY, both ends of the cable itself will be SQUARED for about the last inch or so on each end. You can probably buy a cable by itself, similar universal lengths, BUT you'll need to snip one end and then place a plastic end on that snipped end. It'll have a dab of adhesive where it slides onto the cable end you snipped. Then possibly a bit of heat can help it set better? This way, you just use the new cable and your existing cable housing. Would be better to get a cable/housing that's possibly a bit long, but has the cable ends already squared-off, to me.

IF you can spin the cable on the end that attaches to the speedo head, then the driven gear the other end of the cable indexes with has a wallered-out hole. IF you spin the cable from the trans end, with a drill motor, it should make the speedometer needle move.

There is/was an older guy up in MI, who specializes in speedometer stuff, that used to advertise in the car hobby magazines. All good reports from him and his products. Possibly somebody closer to you?

Just some thoughts,
CBODY67
 
Thanks. I should have mentioned that I threw the old cable away. :(

QUOTE="CBODY67, post: 739702, member: 475"]There are probably some replacement parts speedo cable assys out there. Internal cable and outer housing. I suspect they'll all be pretty much the same quality. Only thing is you'll need to know the length of your current housing. HOPEFULLY, both ends of the cable itself will be SQUARED for about the last inch or so on each end. You can probably buy a cable by itself, similar universal lengths, BUT you'll need to snip one end and then place a plastic end on that snipped end. It'll have a dab of adhesive where it slides onto the cable end you snipped. Then possibly a bit of heat can help it set better? This way, you just use the new cable and your existing cable housing. Would be better to get a cable/housing that's possibly a bit long, but has the cable ends already squared-off, to me.

IF you can spin the cable on the end that attaches to the speedo head, then the driven gear the other end of the cable indexes with has a wallered-out hole. IF you spin the cable from the trans end, with a drill motor, it should make the speedometer needle move.

There is/was an older guy up in MI, who specializes in speedometer stuff, that used to advertise in the car hobby magazines. All good reports from him and his products. Possibly somebody closer to you?

Just some thoughts,
CBODY67[/QUOTE]
 
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