The T-10 was the first 4 speed passenger car trans available back before the Muncie came along. B-W made it by redesigning their T-85 heavy duty 3 speed and moving the reverse bits and pieces to the extension housing, leaving room in the main case for another forward gear.
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!