One of the problems with the SM420 and similar transmissions is the sheer mass of some of the gears. The synchronizer has a difficult time getting enough of a grip on the gears to match the speed of the two parts that are trying to mesh due to the inertia of the spinning parts. Super slippery lubricant defeats the purpose of the brass friction rings in the synchronizers.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!