2052006 10 Posted December 28, 2006 I fear this might be a bit of a silly question, but it confused me when it happened! With the drivers wheel in the air (front o/s on axle stand) I started the engine and the wheel started spinning - not in gear - why is this? Is this to do with the differential, as it stopped when I depressed the clutch. Anyone enlighten me? Share this post Link to post Share on other sites
jackherer 543 Posted December 28, 2006 I believe its caused by drag in the gearbox, its perfectly normal behaviour. If you had grabbed hold of the wheel by hand it would have been pretty easy to stop it turning. Share this post Link to post Share on other sites
jim21070 2 Posted December 28, 2006 (edited) Yep, entirely normal diff action and friction caused the gearbox oil driving the gears around freely in the gearbox. Just enough power was being transmitted like this to spin the diff and driveshaft because it was "off load". I term this "windmilling" but this may not be the correct term for it. The effect you saw is the basis of an automatic gearbox torque converter whereby oil transmits torque between two turbine rotors. One wheel spun because the diff has a natural tendency to transmit all torque to a wheel that is able to freely spin. You saw one did and the other did not. If one wheel can freely spin it gets everything and the other nothing. LSDs (Limited Slip Differentials) overcome this by transmitting some torque to the other wheel even if one wheel is spinning freely. EDIT: Sorry Jackherer, I guess we were typing at the same time... Did not see your replay until I submitted mine Edited December 28, 2006 by jim21070 Share this post Link to post Share on other sites
2052006 10 Posted December 28, 2006 Cheers for confirming that! Share this post Link to post Share on other sites
