loud noise when in park in engine on 1999 Ford Expedition

my engine makes a loud knocking noise when in park and when I shift to drive it stops but when driving my 4x4 sensor light flashes when driving and my radio goes in and out

Asked by for the 1999 Ford Expedition
scan trans codes or get a free diag and est from aamco then post results b4 repairs are made
1 more answer
The knocking noise is just a guess from not hearing the noise, possible torque convertor nuts or flywheel. Electrical needs to be diagnosed.