If I have to vote, then I vote for the oil pan.
Engineers checked their AT in the shop with the pan on level surface.
The problem with tranny in the car is that: it is not parallel with the car.
In the FWD car, it is tilted a bit (not much but it is).
In the RWD car, the trans is titled down at the rear a bit b/c the driveshaft points downward to the rear.
Just place a leveler on the oil pan.
But I have to confess, for my 98 Volvo and 2007 Honda Odyssey van, I simply do it with the car on flat driveway surface.
Last edited by cn90; 12-31-2012 at 08:46 AM.