I just replaced my speedometer with a 130mph one from ebay. It works but is not accurate at all. It is extremely slow for the speed i'm going. What could be the problem? Am i forgetting something? Did i do something wrong?
Thanks

 

As you might know, the speedometer gets its signal from a spinning cable connected to the differential (not an electrical signal like modern cars). When you swap speedometers with a different speed range, you also need to change a little sprocket in the diff, or else the ratio will be all off, thus screwing up your reading.

 

The strange thing is I heard that if you leave your factory speedometer cable in place, the gauge swap will be accurate.

Did you swap anything with the transmission or speedometer cable?

 

No, the only thing i changed was the speedometer. If i need to swap gears where do i get them and how do i know which one to get? Any help will be appreciated.
Thanks

 

Unfortunately, I do not know where to get the little sprocket/gear. I would think Motorsports Auto would have them, or be able to tell you more. I do know that they are different colors to differentiate them though.

 

Your 81 should come stock with a 3.9 The '79 you get the 130mph speedo from I think most have 3.54 rear. If the speedo is calibrated to a 3.54 then it would make more sence that it reads faster than you are traveling, not slower than you are going.

My guess is the speedometer is messed up or the connection into the back of the gauge is loose. Your cable and stock speedo gear should be ok to leave in place...

If your 81 is a turbo, well then it has a 3.54 just like the 79 so there's no problem there.

Maybe the guy on eBay had a bad gauge so he sold it off... "as-is" :doh: