speedometer works strangely - The 1947 - Present Chevrolet & GMC Truck Message Board Network

jimfulco · 02-08-2004, 02:00 AM

My '79's speedo has lost its mind. It reads inconsistently after 10 to 15 minutes of highway driving (70-80mph). With the cruise control (aftermarket, uses driveshaft magnets) set at 75 or 80, the speedo will sometimes go down to 65 for a while, sometimes as high as 95. I finally caught the thing jumping 8mph or so upward yesterday when I hit a bump, & I can't figure out what would cause this. It doesn't wag back & forth like it has a dry cable, it just reads wrong. Any ideas?

Blue Beard · 02-08-2004, 10:33 AM

Probably need to lubricate it.............its metal to metal inside the tubing

jimfulco · 02-09-2004, 01:37 AM

Probably needs it, but would lack of lube make it read a steady 65 or 95mph when I'm actually doing 75 or 80?

79BIG10 · 02-09-2004, 03:03 AM

Not sure but wouldn't hurt. Spray some white lithium grease down the tube. Best way to do this is to take off the speedo from the bezel and spray grease down the tube. This will help keep it from jumping around.

jimfulco · 02-09-2004, 03:50 AM

It doesn't jump around. It just reads low sometimes, & high sometimes.

02-08-2004, 02:00 AM	#1
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	speedometer works strangely My '79's speedo has lost its mind. It reads inconsistently after 10 to 15 minutes of highway driving (70-80mph). With the cruise control (aftermarket, uses driveshaft magnets) set at 75 or 80, the speedo will sometimes go down to 65 for a while, sometimes as high as 95. I finally caught the thing jumping 8mph or so upward yesterday when I hit a bump, & I can't figure out what would cause this. It doesn't wag back & forth like it has a dry cable, it just reads wrong. Any ideas?

02-08-2004, 10:33 AM	#2
Blue Beard Registered User Join Date: Jan 2003 Location: Washington State Posts: 8,834	Probably need to lubricate it.............its metal to metal inside the tubing __________________ 1970 Chev CST 2003 Harley Fatboy 1975 Chevrolet Step Van 1956 Chev Bel Air 1977 Blazer 2WD For Sale $3000.00 1978 Blazer 2WD For Sale $7000.00 1978 Silverado 2005 Monte Carlo

02-09-2004, 03:03 AM	#4
79BIG10 I'm back with 2nd truck! Join Date: Feb 2002 Location: Texas Posts: 3,775	Not sure but wouldn't hurt. Spray some white lithium grease down the tube. Best way to do this is to take off the speedo from the bezel and spray grease down the tube. This will help keep it from jumping around. __________________ 1979 Chevrolet Bonanza Big10 "Tootsie Roll" 1985 Chevrolet Silverado (wife's) Member of the Southern Bowties Club "Don't underestimate how sexy a fat man who drinks to excess can be." Homer Simpson

02-09-2004, 01:37 AM	#3
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	Probably needs it, but would lack of lube make it read a steady 65 or 95mph when I'm actually doing 75 or 80?

02-09-2004, 03:50 AM	#5
jimfulco Registered User Join Date: May 2003 Location: Shreveport LA Posts: 3,170	It doesn't jump around. It just reads low sometimes, & high sometimes.



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