Transmission Woes with No Fault Codes

My 2000 S-Type with the Ford 5R55N transmission is having issues. Everything was fine with no problems until it decided it did not want to go anymore. It shifts into each gear and I feel the gearbox engage, but it will not move without revving up the RPMs and then just barely. I’m not showing any fault codes either.

I had already planned on changing filter and fluid so that has been done, but still no improvement.

Any suggestions of what to look for next?

Thanks,
Donald Coleman
2000 S-Type
1991 XJ40 Sovereign

I hope this isn’t too obvious to ask. Are the brakes dragging ?
A neighbor had that happen on his old Plymouth. Took a while to find.
The parking brake light was burned out and it was lightly engaged.

Welcome Donald.
If it isn’t the brakes, there are solenoid valves in the trans that can give problems.
There is a known problem with the 5R55N and other variants of this trans at high mileage. There are two servos on the right hand side with steel shafts, which fit into holes in the aluminum case. The steel gradually wears the aluminum hole a bit oversize.
The Ford approved fix is to ream them out and install steel sleeves.
An entrepreneur in Wisconsin has come up with an alternate, which I installed. I wrote it up here:

5R55N_trans_parts%20001