Even my brother could handle this one, Grace.

Dear Car Talk

Dear Car Talk | Sep 01, 1991

Dear Tom and Ray:

The speedometer needle on my '81 Pontiac Gran Lemans jumps all over the place. The car has 57,000 miles on it. This seems to be an intermittent thing, so I've been hesitant to take it to my mechanic. Will this be an electrical problem, or can any mechanic fix it if necessary? Please help this little, gray-haired old lady. Thanks.

TOM: Well, we have good news, Grace. It's probably not an electrical problem, and almost any mechanic should be able to fix it (even my brother could handle this one, Grace).

RAY: It's probably just a worn speedometer cable. The speedometer cable runs from the transmission to the back of the speedometer gauge on the dash?board. That cable is housed in a plastic sheath. The faster the cable spins, the higher the reading on the speedometer.

TOM: But when the cable gets old, it sometimes starts to fray. And if it frays enough, it can get caught on the inside of the sheathing as it spins around. And that's what makes the needle jump.

RAY: A new speedometer cable should cost you about $50, and there's a good chance it'll make the problem go away. If it doesn't, there may be something wrong with the speedometer itself (the part in the dashboard). A new one can be rather expensive, but maybe you can talk your mechanic into finding a used one for you at a junkyard. Try that "little old gray haired lady" line; it worked like a charm on us!

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