I just installed another transmission in my car and while it was down I installed a guage cluster from a 89 IROC that has a 145mph speedo. Well all the gauges work except the speedo. It always reads 10mph faster than its really going. At a dead stop it shows 10mph and the trip meter doesnt work either...i dont care about the trip since the other one i have didnt work but whats up with the speedo?