I have a 2005 crown vic with 4r70 transmission with 335 000 km.
Ever since I got it, it has a transmission bug but im able to work around it since then
Now I decided to investigate it. The trouble is a neutral delay between either the 3 and 2 or 2 and 1. Im not sure which one.
There is no problem up shifting. The problem occur when turning only and then accelerating. Seems to me it goes to downshift and theres no oil to do so. THen the car stabilise after a second and the transmission shift perfectly.
What Ive done so far:
I dropped the pan and replaced all the springs and the piston that is accessible without removing the valve body. The piston is located on the front and driver side of the transmission oil pan.
The transmission never ever slipped ON a gear. It goes in neutral and it's obvious when it gets back in gear. The shifts are always firm, just like any police crown (firmer than the civilian though)
I can sometime do the same bug doing an american stop. It looks weirdly like a fluid starvation, but I found no broken srping or dropped filter in the pan.
a replacment is 900$, rebuilt unit, around here