[FortyfiveD]

Its Transmission Fluid. I replaced all the replaceable part (the speedo cable, O-ring, and gasket/seal) short of pull the trans apart. I don't think it's the trans because this has happen with two different transmissions (doesn't mean it can't happen though) . Also to answer the question about the rearend I have a custom built racing rearend with a 4:88 gearing ratio, so the car stays in the higher RPMs longer.