transmission slips

When I leave the park. to drive, my transmission slips for 2 3 seconds after she drives normally. It does not slip in normal driving,

if accelerates quickly Transmission slips when changing speed.

The reverse speed works well, instantly.
I check the oil pressure ok,
I check the arm speed selector ok
I check the resistance of the sensor range, ok too.

The oil has been replaced and filter at (127000) KM and the level is good. I added an additive for oil transmission and always the same problem.
Crown Victoria 1996, 4.6L 130,000KM (70,000 mi)
any idea what could be wrong?

The reason it doesn't immediately go after shifting from P into D when cold is that the pump isn't building up pressure. The slipping when shifting is most likely due to worn clutch packs. If you can't live with it the way it is you will have to get it overhauled.

Thanks for you reply, But could you tell me why after a short period of time my transmission run just fine? first in the morning when i start my car, i put in drive and i feel slip, and more i give gas, more my car try to advance, and it takes 5 or 10 second and it run like never happend..if it is the clutch packs i would have this problem all the time?
I did check oil pressure at idle, on EPC the acceptable range is 15 to 25 PSI my reading was 25 PSI, the line pressure range is 84 to 128, I had 100 PSI, I try reading on WOT Stall, but because of my gauge i cant not tell the exact pressure but it was very hi, over 200.
I don’t know why but my book said to check pressure only on R position.
what is bug me more is this transmission is controlled electronically, maybe a bad signal or.....
Thanks again it is verry helpfull.__________________

You can buy a solenoid pack and try replacing it. You could do this on a day off. I changed one on my F-150 1997 and it was around $60.00 but this was around 1999. Just buy a new pan gasket and filter and the valve body. Just unplug it and I think 6 torx screws hold it in place. Unplug it before starting the job.

Finaly i bring my car to a transmission rebuilter, they open the transmission and found the band was almost destroy, it cost me 1500,00$ plus tax to repair it,
thanks to all post in this forum for me, you are all verry nice.