Speedometer - JeepForum.com
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post #1 of 8 Old 01-27-2020, 07:40 AM Thread Starter
Shensms
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Speedometer

I have a 1980 CJ7. The speedometer is now going only up to 15 MPH, and wonít read faster speeds. Has anyone seen this before? Is it more likely to be the gauge or the cable?

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post #2 of 8 Old 01-27-2020, 08:50 AM
gutthans
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In my experience with cable-driven speedos, what you describe is often the result of a worn-down cable end prong. The plastic ends can gradually wear and 'round-off'. They continue to turn and drive the speedo by friction rather than square-drive engagement.

This is very easy to check, of course, and eliminate as the cause. Unscrew the easiest end coupling to get to and pull the cable out to check each end for wear. Reverse removal to reinstall.

That should eliminate the cable as a cause.
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post #3 of 8 Old 01-27-2020, 10:58 PM Thread Starter
Shensms
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Thanks, Iím assuming in that situation the fix is to replace the cable.
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post #4 of 8 Old 01-28-2020, 06:49 AM
bob4703
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Start there. There is a rubber stop on one end of the cable--forget which end--and you need to put it back on in the same place on the new cable. Remove the cable and housing on both ends and inspect the housing for wear. If nothing is obvious just replace the cable itself. While you have it loose look closely at the speedometer gear the cable goes in on the transmission end. That could be a problem too. The hole the cable goes in the gear and the speedometer head should be square and not rounded as should both ends of the cable.

You can buy one size fits all replacement cable that you cut to fit. I never had much luck with those but you might. When my speedometer went haywire I ordered a complete cable and housing but couldn't get the rubber plug that goes through the firewall in place. It was also very stiff so I pulled the new cable out and used the old housing. You can order the cable by itself. 4X4 shops may have them in stock and may be able to make them. Any option you take for a replacement cable won't be expensive.

If your speedometer continues to act up after cable replacement and the gear looks good then the fault lies with the speedometer itself. I won't weigh in with recommendations for replacements. I wouldn't replace a speedometer head without replacing the cable.

You haven't filled out your profile so we don't know where you live or how long you've owned your Jeep. If you or a PO used oil to lube the cable colder weather will make a speedometer go crazy.

Good luck!

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post #5 of 8 Old 01-28-2020, 09:59 AM
gutthans
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Quote:
Originally Posted by Shensms View Post
Thanks, Iím assuming in that situation the fix is to replace the cable.
Yep. That would be the simplest and most cost-effective thing.
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post #6 of 8 Old 02-18-2020, 06:30 PM
boutdoorhunter
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Mine is acting up. I replaced the cable. The gears are in good shape. The gears on the speedo itself looks good. Looks like it is driven by centrifugal force. Any idea what happens to them?


Quote:
Originally Posted by bob4703 View Post
Start there. There is a rubber stop on one end of the cable--forget which end--and you need to put it back on in the same place on the new cable. Remove the cable and housing on both ends and inspect the housing for wear. If nothing is obvious just replace the cable itself. While you have it loose look closely at the speedometer gear the cable goes in on the transmission end. That could be a problem too. The hole the cable goes in the gear and the speedometer head should be square and not rounded as should both ends of the cable.

You can buy one size fits all replacement cable that you cut to fit. I never had much luck with those but you might. When my speedometer went haywire I ordered a complete cable and housing but couldn't get the rubber plug that goes through the firewall in place. It was also very stiff so I pulled the new cable out and used the old housing. You can order the cable by itself. 4X4 shops may have them in stock and may be able to make them. Any option you take for a replacement cable won't be expensive.

If your speedometer continues to act up after cable replacement and the gear looks good then the fault lies with the speedometer itself. I won't weigh in with recommendations for replacements. I wouldn't replace a speedometer head without replacing the cable.

You haven't filled out your profile so we don't know where you live or how long you've owned your Jeep. If you or a PO used oil to lube the cable colder weather will make a speedometer go crazy.

Good luck!

It's hard to keep your mind and your mouth open at the same time!
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post #7 of 8 Old 02-19-2020, 10:36 AM
gutthans
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Originally Posted by boutdoorhunter View Post
Any idea what happens to them?
..."to them." being what? There is also an internal tranny gear, that rarely goes bad, but it's a possibility.
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post #8 of 8 Old 02-19-2020, 01:04 PM
boutdoorhunter
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The gear is good. It is in the speedo itself. Runs at 45 sometimes at 80. It also sticks at 15 when idle sometimes.

It's hard to keep your mind and your mouth open at the same time!
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