rear wheels locked up while backing down a grade

I put it in drive and was able to get back up to the level parking area of my driveway but now it won't move backwards at all in reverse or neutral. It's cold now and I started it up and could feel it go into reverse but it wouldn't move and it stalled. I tried pushing it forward and it seemed able to rock forward like when you are hand pushing a car and you have to rock it forward and back before you can get it moving. It started to rock forward but not back. The tranny fluid looks light brown and thin, after I got fluid, filter, and pan gasket service about 2 months ago. I've had the car for 8 months and put 17,000 miles on it in that time. I don't use the parking brake so I'm really having a hard time trying to imagine what could be causing this problem. I would really appreciate hearing from anyone who knows what this is.

You may not use the parking brake, but it sounds like it may be locked up.

I put it in drive and was able to get back up to the level parking area of my driveway but now it won't move backwards at all in reverse or neutral. It's cold now and I started it up and could feel it go into reverse but it wouldn't move and it stalled. I tried pushing it forward and it seemed able to rock forward like when you are hand pushing a car and you have to rock it forward and back before you can get it moving. It started to rock forward but not back. The tranny fluid looks light brown and thin, after I got fluid, filter, and pan gasket service about 2 months ago. I've had the car for 8 months and put 17,000 miles on it in that time. I don't use the parking brake so I'm really having a hard time trying to imagine what could be causing this problem. I would really appreciate hearing from anyone who knows what this is.

What year is your Vic? Unfortunately it looks like it might be transmission time. It sounds like something broke inside the transmission. Possibly a mechanical diode failure.

My Crown Vic is a 2008 police interceptor model. I haven't ruled out a parking brake malfunction. That would probably be the easiest fix. A friend of a friend said his 90s model crown vic had a reverse lockout solenoid known to cause bizarre problems. I'm just getting up and having coffee. I haven't called my mechanic or the business associate who sold me the car yet. That can wait til after my third cup of coffee. Here's hoping that I don't need a new transmission. Big expenses don't come easy for a small one car taxi company.

It sounds like your rear brakes have automatically adjusted them selves too tight. Not uncommon with many modern vehicles; The Crown Victoria features 4 wheel disc brakes, but, these wheels have small brake shoes & a brake drum, to take care of parking brake and road side servicing ( flat tires, etc.,) any reputable mechanic, or brake shop can probably re adjust them for a
nominal fee, I hope I responded in time to save you some money with this.