79 speedo cable
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
79 speedo cable
I have a 79 with cruise. Originally TH350 now has a TKO 600. Speedo started jumping very slightly last fall before I put it away, and there is a faint clicking noise coming from under the dash. Obviously the possible causes include the speedo head, the cables, and the cruise transducer. I'm thinking of trying the cables first since they are both 37 years old and my experience tells me that is the most likely cause. Couple of questions: Can I lubricate the cable from the cruise transducer to the speedo head on the car if I disconnect it at the transducer and slide the cable out of the housing? Is there merit in lubricating the cables or should I just plan on replacing them? And what is the best cable lubricant to use now that GM doesn't have their ST640 available any more?
Pro
Joined: Aug 2007
Posts: 707
Likes: 31
From: Pitman NJ
If there is a bad cable, more then likely it's the lower cable. As the transducer wares/gets old it becomes harder to turn. This will put more tension on the lower cable. The upper cable basically has no tension on it.
On my 79, that is what happened. The speedo started jumping...then just stopped, and it was the lower cable that snapped. Since my cruse wasn't working anyway, I put in one long cable, and bypassed the transducer.
I"m not sure if you can lubricate the cable without removing it.
I hope this helps.
On my 79, that is what happened. The speedo started jumping...then just stopped, and it was the lower cable that snapped. Since my cruse wasn't working anyway, I put in one long cable, and bypassed the transducer.
I"m not sure if you can lubricate the cable without removing it.
I hope this helps.
Melting Slicks
Joined: Oct 2000
Posts: 2,143
Likes: 195
From: Englewood FL
I have a 79 with cruise. Originally TH350 now has a TKO 600. Speedo started jumping very slightly last fall before I put it away, and there is a faint clicking noise coming from under the dash. Obviously the possible causes include the speedo head, the cables, and the cruise transducer. I'm thinking of trying the cables first since they are both 37 years old and my experience tells me that is the most likely cause. Couple of questions: Can I lubricate the cable from the cruise transducer to the speedo head on the car if I disconnect it at the transducer and slide the cable out of the housing? Is there merit in lubricating the cables or should I just plan on replacing them? And what is the best cable lubricant to use now that GM doesn't have their ST640 available any more?
I did lubricate both cables with a cable lubricant.
To lubricate the cables you pull the cable out from the sleeve. They only pull out from one end. The speedometer cable pulls out from the speedometer end. I cannot remember from which end the transmission cable pulls out. Then put some lube in the sleeve and start feeding the cable back in. Add more lube as needed as the cable is pushed in the sleeve. Do not lubricate the cable end close to the speedometer to keep lube out of the speedometer.
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
I also have a 1979 and had a problem with the speedometer needle jumping. It turned out the cruise transducer was bad. To test for this, remove the cable that runs from the transducer to the transmission. Then spin the shaft on the transducer that the cable was attached to. If it does not spin easily, the transducer is the problem. I replaced the transducer.
I did lubricate both cables with a cable lubricant.
To lubricate the cables you pull the cable out from the sleeve. They only pull out from one end. The speedometer cable pulls out from the speedometer end. I cannot remember from which end the transmission cable pulls out. Then put some lube in the sleeve and start feeding the cable back in. Add more lube as needed as the cable is pushed in the sleeve. Do not lubricate the cable end close to the speedometer to keep lube out of the speedometer.
I did lubricate both cables with a cable lubricant.
To lubricate the cables you pull the cable out from the sleeve. They only pull out from one end. The speedometer cable pulls out from the speedometer end. I cannot remember from which end the transmission cable pulls out. Then put some lube in the sleeve and start feeding the cable back in. Add more lube as needed as the cable is pushed in the sleeve. Do not lubricate the cable end close to the speedometer to keep lube out of the speedometer.
Racer
Joined: Dec 2014
Posts: 374
Likes: 42
From: Coldwater Mi
My '79 cable was jittery & makin' some noise.....I already had that portion of the
dash out to fix the tach, so I disconnected the speedo cable, at both ends, so I could
see when the lube was coming out of the tranny end as well.....put it back together,
and it's been nice & smooth & quiet ever since!!
dash out to fix the tach, so I disconnected the speedo cable, at both ends, so I could
see when the lube was coming out of the tranny end as well.....put it back together,
and it's been nice & smooth & quiet ever since!!
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
I've been shopping around for a suitable lubricant. Years ago it was a common product and I'm pretty sure I have a tube of it around someplace, but do you think I can find it? And nowadays no one has heard of the stuff. What is an appropriate lubricant for a speedo cable these days?
Melting Slicks
Joined: Oct 2000
Posts: 2,143
Likes: 195
From: Englewood FL
I've been shopping around for a suitable lubricant. Years ago it was a common product and I'm pretty sure I have a tube of it around someplace, but do you think I can find it? And nowadays no one has heard of the stuff. What is an appropriate lubricant for a speedo cable these days?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Thread Starter
Melting Slicks
Joined: Dec 2009
Posts: 3,233
Likes: 657
From: Thunder Bay
Burning Brakes
Joined: Sep 2010
Posts: 799
Likes: 26
From: Lexington Park Maryland
I have not done this to the 79 I am reviving, but I did lubricate the cable for my 72 LT1 when I installed a new cable. I used the same grease used on the CV Joints. Removed the core (cable) and coat it with that grease, then I use a grease attachment to force grease in the housing so when you re-install te cable it will force the grease in the housing.
Melting Slicks
Joined: Oct 2000
Posts: 2,143
Likes: 195
From: Englewood FL
Safety Car
Joined: Nov 2008
Posts: 4,368
Likes: 9
From: Colorado
Mine was jumpy and then froze years ago. I disconnected the transducer to speedometer cable and chucked the transducer end into an electric drill. Run the drill in REVERSE and apply minimal lube while running. I used WD40 sparingly and the gauge has worked well ever since.