Originally Posted by kanishkl
Just wondering, what is the reasoning behind not revving at P?
Way back in the day, BMW had issues with automatic transmissions not completely disengaging after having had a gear selected. This caused massive problems in some states which used tailpipe sniffer emissions tests (this was before OBD2) that involved a say 2500 RPM no load test, people would show up, leave the car running, then rev the engine to 2500 in P or N for the test and the trans would eat itself.
I've also heard some horrific noises from old Warner Gear DG-series trans (Studebaker, Jaguar, etc.) when revved in park with a slightly misadjusted throttle linkage and/or a worn torque converter clutch...
In short, it's not recommended...