BluegrassMotorsport

I am sure this is a question asked often, but I do need help.

When cruising in my 1977 coupe a while back, I was cruising along at what I thought was 60mph. But then, I get my doors blown off my a minivan. Strange as it seems, I kept on driving. A few moments later, a Silverado blitzes by me as fast as the mini van did. Looking through my rear view mirror, I saw a whole string of traffic about to do the exact same thing.

So, I sped up. I actually kept speeding until my speedo read 80mph, at which point I began to slowly pass the flow of traffic.

This leads me to highly believe that my speedometer is off. Does anyone know how I would go about fixing the problem? I have had the car for about five years, but have not been able to drive it often (Grandfather bought it for me, and will not let me drive it often). I don't really know a lot about the maintenance on them lol.

72LS1Vette

Stick a GPS usint in the car to see if the MPH matches between the GPS and your speedometer. If it's off maybe the rear end gearing has been changed at some point or perhaps you have a different transmission?

There are different speedo drive gears available to correct the problem once you know what the problem is.



Rick B.

7T1vette

Or, time one mile distances (highway mile markers) to see if you are at 60 second intervals. You can calculate your actual speed by setting speedometer at 60 mph then measuring time for one mile. Then divide 3600 by the number of seconds to calculate actual speed. {Using a GPS is easier.}

Vette5.5

While all those suggestion's are fine, probably easiest to have a friend in a late model car run along with you on the highway in phone contact, and see what happen's. Don't forget to check the odometer's in syc too, by just driving with the speedo indicating 60mph for 60 second's = 1 mile. Good information to have before messing with drive gear changes, as maybe the speed reading's actually off.

John A F

If you are driving on some of the interstates In New York I use to commute to work, everybody is driving 80 miles per hour or faster.

7T1vette

Same with Chicago and Phoenix. However, L.A. average interstate speed is about 14 mph....