I got 5600 miles on my z and i just got a new tranny and a clevis pin. Everything seems to be fine except for the fact that my 3rd gear and higher slips act at certain rpms. Could this be due to the fact that the gears slip when the flywheel spins act the same rate as the gear i'm in. I heard this is the method used in power shifting, but what my question is do I need to have my car serviced again?