[gary678*]

Hi, If the tires are new the problem may lie in either the speedometer itself or in the speedometer gear assembly. Removing the assembly is easy, just two small bolts. Check the number on the housing; for a 3.78 rear end it should have 19 stamped on it (19 gear teeth). Since you are reading fast more gear teeth are needed to slow down the reading. Your reading is just a little bit fast so I think a 20 would put you spot on. Good luck! Gary