hdc inactive and air susp inactive

2004 vogue 4.4 v8
hi everyone,
can anyone help me with the following issues:
(1) I get air susp inactive and hdc inactive when I drive for a while, once I switch off the car and I restart it the fault goes away but after driving around it comes back
(2) very strange right side speakers suddenly stopped working after I replaced my battery, but when I disconnect the battery and I reconnect it back the radio works fine all speakers working for a few seconds then the right side (driver's side goes silent) if I adjust the sound balance all the way to the right no sound comes out
(3) when I drive at a constant speed lets say 50km/h, I can hear a grrrrrrrrrrr sound (you know the markings on the edge of the road the dotted lines when you drive over them to wake you up in case you are sleeping while driving? well it sounds like that) i can hear it from under the car at the center it comes for a few seconds then silent when it does this it affects the revs, lets say the rev is at 2000rpm when the sound appears the rev needle jumps approx 100rpm and increases a little then the grinding sound goes away then it comes back and it does the same thing the rev jumps 100rpm then it goes away, you cant feel it at high speeds but the sound comes and goes intermittently even at high speeds (TORQUE CONVERTER? MEYBE? ) also sometimes the car vibrates when shifting gears at low speed, early in the morning on a cold start if I don't wait for the temp gauge to reach normal temp at the center it and I put reverse or drive the gear engages harshly but after warm up its smooth shifting (no transmission fault)

problem 1 and 2 appeared after I replaced the steering rack and all front bushings