87 speedometer problems

[Sassan]

I have a 87 supra n/a 5 speed. my problem is that my speedometer is all wacked out. wen driving it reads about 20 mph faster than im going. so it will say im doing 85 wen only doing 65. wat would cause this problem?

 

[I6Boost]

When your car is completely still and not moving does it still read 0?

 

[Sassan]

yes it still reads 0 and doesnt move at all till i start moving

 

[mk3-4-me]

do u have the stock tires on it? cause throwing different size tires can mess up the speedo.

 

[Max Vador]

what is the standard tire profile cause i'm not sure if mine are stock size or not. mine also wonks out exponentially so i originally thought it was that too. and i don't wanna go tinkering with the speedo needle or gear yet

 

[mkiiichip]

Do you know the history of your diff? Has it been changed?

 

[Max Vador]

pretty sure not since mine isnt a LSD so why would they bother with another non-posi?