Why must car start in P or N and not D.

[Dr. Jerryrigger]

Originally Posted by ShadeTreeMech

However, beware of the lock up torque convertor trying to engage in such a situation. Bad things can happen if the spped is high enough and the computer send the signal to the convertor to lock up.

Otherwise, no harm no foul assuming the torque convertor remains unlocked. which is to say being in 2nd is safer than being in D with the engine off during a coast.

My car is good about this unless I do a good job of rev matching on the highway, then it engages with a thud. But at least it's never more than 150 RPM difference. I don't bother rev matching any more, and things go smoother.

[dwtaylorpdx]

Safety switches pre-date that by a lot, the first Powerglides had them... My 1957 ford fairlane has one as well.

When 4 wheeling in rocks its very common to stall a vehicle engine and restart in gear because if you hit the clutch you will go backwards down hill very fast. BAD>>>>

The Torque convert as well as the transmission pump and hydraulics are all turning when you crank the starter, its just bypassing until you switch the auto to a gear that engages a planetary and puts power to the road... Much like that AC clutch....

Dave