Slipping Clutch


When the clutch can no longer hold the engines power (keep the trans input shaft at the same speed as the flywheel), slippage occurs resulting in intense heat and lost power.  This heat burns the clutch material releasing smoke and a rank smell.  Slippage is normal during take off / launch but if it occurs during an acceleration, a clutch replacement is just around the corner.


Launches with excessive slippage (slow release of clutch at high engine speeds), and to a lesser extent, aggressive shifts can dramatically shorten the life of a clutch.  The following datalog shows the beginning of the end for my last clutch; an RPS unit which had a much longer life than the previous Centerforce and OEM clutches.  Look at the red line (engine speed) while at WOT.


The fact that the rpms increase, level off, and then drop while at WOT indicates a definite problem.  To see just how bad the clutch in the above datalog is, I compared it to a run made several weeks earlier before it started slipping (see below).



Both of these runs represent a WOT acceleration in 3rd gear on 15psi boost.  The bad clutch begins slipping at ~3,750 rpm and at one point results in ~1,500 rpm difference between the flywheel and input shaft.  By ~5,200 rpm, the clutch no longer slips.  The heat created during slippage represents lost power, therefore a slower overall vehicle acceleration.


Outside of high rpm launches or slow clutch releases, slippage is most likely to occur in higher gears when the engine is producing peak torque.   For example, I could not get the clutch to slip in first, only slightly in second, and quite a bit in third.  Fourth gear at peak torque would have been a reckless driving ticket (at least 20mph over the speed limit).




since August 7th, 2002


Last Updated: 08/08/02 07:50 PM