speedometer inaccurate after swap st165 to st205

i put the st165 manual speedometer setup in the st205 tranny. i did happen to change out the gear that goes in the transmission and swapped it to the st205 gear thinking that it may have a different number of teeth. now when i drive the speedometer reads 10-20mph higher than normal. when i'm doing 80mph it says i'm doing 100 on the speedometer. My wheel and tire size are close to oem diameter so i dont think it is that.

did anyone else do a st205 swap into a st165? is your speedo accurate?

Mine is perfectly accurate above 10mph. It doesn't register anything below 10

thanks for the reply, i think i just need to replace the part that controls the needle, the odometer reads correctly, i just went 50 miles on gps and it was 50 miles on the odometer even though i was going 70mph on gps but the gauge read 90mph.

That makes no sense, they are driven by the same mechanism I believe...

no, the speedo needle is magnetically driven and the odometer is gear driven.