" From: Tom Jennings <tomj@xxxxxxx> " " " " The efficiency of an automatic transmission is pretty good; " somewhere in the upper 90's percentage-wise. what about those figures we've heard about 25hp to spin a tf904 and 40hp for a 727? manual trannies are 98-99%. " Horsepower NOT sent to the wheels becomes heat. true. where else could it go! " It's about 770 watts per horsepower if I recall. Here's chart " showing how much heat is produced: close enough for your estimates, but exactly 746w sae 736w metric the sae number is a conversion from something like 33000 ft-lbs/minute. the metric is similar, rounded to metric units [4500 kg-m/min?] ________________________________________________________________________ Andrew Hay the genius nature internet rambler is to see what all have seen adh@xxxxxxxxxxxxxxxxx and think what none thought