quite true nelly
sorry bbsal , but that was a way off guess
i know you are trying to help
but some people will take it to heart ,
as i heard it on a lexus site so it must be true
and would fight with there friends saying O/D is a gear
lmao
but that is there problem
so any way
the tranny has 4 gears[ except the newer 02-03 with a 5 sp tranny)
i think the new bmw 745i has a 6 speed auto and so will the new 5 series]
in 3rd and 4th the torque convertor can be allowed to lock up causing a mechanical coupling
rather than a fluid one
turning off the od usually only helps if you are on a 50 miles road with lots of stops
now when the car gets to a cruising speed it will say i no longer am going to be changing gears and the load is light on the engine
it will the use the TC to lock the 2 seperate halves of itself together
now the fliud that used to be pushed by the spline connected to the engines crankshaft witll physically connect and remove the fliud power loss
now some people may say
"yah i always knew autos were crappy for power loss , manual all the way, it rocks"
well they must also like winsheild washer blue lights
as they do nothing for you
the fluid connection is perfect for any high rev engine with 800-1000 hp easy, just ask a 300zx or a supra
why?
it creates a perfect base to launch and shift
it lets the engine get up to speed
( stall speed,when you have a foot on the brake and one on the gas)
and stay there for max torque for the launch
this helps kep the tires on the track not in one spot
it also is that an auto tranny can shift much quicker than a man can
so this saves drivetrain losses and turns it into speed
oh yah the 4th gear is not a one to one ratio the 3rd is usally close to a 1 -1
the 4th overdrive gear is usually 1.25-1 so the wheels turn 1.25 revolutions to one of the engine