Wacky speedometer 78 mc

[spongbob]

Okay not to important but it is the gbody forum!... my speedo floats up and down past whatever speed I'm going it will pass up the speed I'm going... and go 30 or 40 miles over the speed I'm making. How dose it do this is the speedo broke? but running off of cobwebs and insect guts ? I suppose someone's ran this down lately care to comment or joke lol thankx..

 

[57 Handyman]

Spongbob, I've always related a bouncy speedo to be caused by the cable binding and in need of a cleaning and lubrication. This maintenance fix isn't very difficult to perform and requires disconnecting the speedo cable at the transmission, removing the inner cable, cleaning it, applying grease, and reinstalling. IF after doing this, the issue still remains, then the problem is in the speedometer itself. Now, replacing the speedometer requires quite a bit more effort. Good luck!

 

[57 Handyman]

Bob, I found this video on YouTube. I was wrong about being able to pull the cable out from the bottom; there is a lock at the top behind the speedometer to prevent this from happening. So, unfortunately, you will have to attack it from the top. However, I would do the little test with a drill to determine if the cable is binding. Again, good luck!

 

[Ugly1]

The other two possibilities if not the cable is the needle may be not attached to the pin or the magnet inside the speedometer is going bad. Both are “repairable “ but the pin is easy with correct glue. The magnet is a send out or find used. 57 Handyman’s answer is probably best to go with and most likely the correct one! If there is a wire on the cable sticking out and catching causing it to bounce/bind.