I have a 94 DX. I picked up a gauge cluster with a tach off of ebay from a 93-95 Civic. Didn't specify the exact year. Install was fine. But the speedometer is progressively off. When the speedo reads 35 I am actually doing 31. When the speedo reads 80, I am actually doing 71. I know it is reading miles acumulated faster than I am actually traveling. Is the speed calculated in the actual Speedo guage, or in the cluster housing, the ecm, ???
Thoughts on why it is so far off.

 

All 92-95 clusters are completely interchangeable and there is no difference in the speed readings. If you are worried you can swap your original speedo in its place.

 

I had the exact same problem from a cluster i bought online. it would read a lot higher than i would be going. like 25 when i would do 15.

But yeah do what danomatic said. you can just take the speedometer out and put your old one back on. there is a few screws in the back holding the speedo on there.

 

I think there are trimmers (adjustable resistors) inside the speedo to calibrate it if slightly off (miles accumulated, I would think is digital; nothing to adjust though). Reading 25 when it should be 15, something has failed. The OP should just swap the old speedometer head back into the new cluster, then the odometer mileage will correspond to the car too.