1998 Ford Taurus Station Wagon SE

Hello,

My 1998 ford taurus wagon se has a tranny problem that has me stumped,it has the AX4N tranny.

Here is the problem
Start the vehicle at anytime,hence being warm or cold it will not shift out of first gear until i hit 5-6000 rpms,the speedometer works fine as well as the rpm gauge.
It takes about 5-10 minutes of high revving during driving the car to make it shift into 2nd
I do have a code p-0500 for the vss

I had the transmission replaced last summer,as well as replacing the vss with 2 different ones in the last 3 days.I also changed the transmission fluid and filter
Still has the same problem and the computer still throws a P500 code,i feel like im going crazy over this issue and am not sure what next step i should take.

Like stated above,after driving the car hard in 1st gear for about 5-10 minutes it will finally shift into second then the car will shift threw all gears as nothing happened but as soon as i turn the vehicle off in that instance of it shifting ok and start it back up it gets stuck in first gear again.