Yes i have a 2011 Ford crown victoria police interceptor and the transmission shift good in drive but lost all power in reverse gear what can i start doing to find out the problem

Unfortunately this is an internal transmission failure - there is no diy repair. Transmission removal and disassembly will be required.

If the engine revs but the vehicle does not move appreciably in reverse, it sounds like the reverse band may be damaged or burned up inside the transmission. How is the fluid level and condition? Any signs of concern there? Further, diagnostic testing can indicate shift solenoid position and gear selected to see if the electronic portion is working properly (I suspect it is).