I am sorry, dont know if its my age or what, but I never heard the term "clutch slip" when starting in a higher gear than 1st (low) gear. In my day, and as a retired truck driver, we just refered to it as "riding the clutch", which means keeping the clutch pedal engaged longer than needed to shift or to drive slowly in any gear, while keeping the clutch pedal engaged. My question is this the same as clutch slippage? I just thought Clutch slippage was due to a worn clutch pressure plate, or throw out bearing.