I hope this is in the appropriate area. It is maybe transmission related. My speedometer is somewhat erratic but not in the normal sense. It doesn't really jump and fluctuate like a bend or kinked cable. It is more like it is accurate up to about 45-50 MPH then it suddenly gets slower, according to my GPS any way. At a constant 2000 RPM it will show 60 but at 2500 it only shows 66 when the GPS shows 75. All of this is with the turbo 200-4R locked up so there is no slip at the converter to account for the disparity. Some of the time it will show 72 when it should show 75 but mostly it won't. The margin for error goes up dramatically with increased speed. Any thoughts on what I should look at or attempt to change? I've cleaned the cable, relubed it and it looks fine. The outer housing has no kinks and the speedo head appears to otherwise work fine.
