Speedometer problem

[gtaa9]

I own a 1986 Monte Carlo . My speedometer is off by 20mph. When the speedo is reading 45mph I'm really doing 65mph. What would be the problem here? Also my fuel gauge isn"t reading right either. I appreciate all the help I can get. Thanks.

 

[1983regal]

The speedo is simple, just need to change out the gears in the tail housing to correct for it being off. Search around there is a calculator that will help you figure out what gears you need for the tire size you are running. Check the power and ground wires at the tank for the fuel gauge, either its a bad sender, loose wire or bad gauge.

 

[gtaa9]

My car has the V6. I know that the 200-4r trans was in both LS SS models. Is the speedo gear differant from the LS v6 and the SS V8 models? If so what color is the V6 and the V8 gears? I had the trans replaced years ago. Im thinking that I have V8 200-4r trans.

 

[gtaa9]

So nobody knows??? Could it be the speedometer itself?

 

[Phoenyx]

It has nothing to do with V8 or V6. it's the rear end gears. So I'm guessing the car your transmission came out of had a different ratio that your car. Do you still have the old one, if you do you can just swap the speedo gears.