89 c2500 stock radio issues

[usa21b]

i am having two issue with the stock radio in my 89 c2500


issue 1 the radio cuts in and out at random when it goes out it sounds like it is grounding out but have check the grounds on the truck and the wiring and have found no faults there. any thoughts?

issue 2 when the radio decides it wants to work there is a whine in the speakers that changes pitch and volume with acceleration. again any thoughts?

Thanks In Advance