prelude speedo is incorrect......help

Any help appreciated... I have a 94 prelude 2.3L, automatic My problem: The speedometer reads approx 10 miles an hr (high)..reading 60 when driving 50 tires are factory size the dealer said speed sensor and shift is fine they said they timed it with a new car....and It was correct. But this cant be....I check it routinely with the use of another car and 2-way radios. The odometer is racking up more miles than actual too...I check it against highway mile-markers.... Something isn't right.....any feedback Thx from: A Honda newbie!!!