everytime start running the speedo gauge starts shaking and bouncing up and down and when i'm going faster i guess 60 or 70 it goes all the way down to 140, all I want to know is what the problem is and what can I do to fix it...
Might try a new speedo cable. Not really for sure. My friend had the same problem and he put a new gauge cluster (out of a junk yard) in and a new speedo cable and it fixed it.
a.) Get some graphite speedomter cable lube & lube up the lower part of the cable. You will have to remove the speedo clutster housing to get access to the cable. There is a pinch clip on the back of the speedo that is a little tricky to get off so tha you can pulll the center part of the cable out. Apply grahite to the lower 1/2 of the cable. Too much lube, and it works its way up into the indicator unit and gums everything up.
b.) Check the cable routing to make sure the cable housing isn't bent or rubbing somewhere. Look closely at the area where the cable runs past the exhaust pipes for heat damage.
c.) Replace the cable assembly: Advance Discount Auto parts has the 5 speed cable, P/N Pioneer Products CA3018, cost $17. I believe that it is the complete cable including the outer housing. It install from the inside of the car first, the speedo cluster has to be removed as in step a.
d.) Replace or have the indicator unit professionally repaired.