Most time radio only works in the back with some static only in front. Static bearble up to a point. Then suddenly you progressively hear the engine or a humming with the static, it culminates into no more radio but an unbearable hissing loud, like a continuous ambulance siren, got to turn the radio off or else you turn deaf. Turn it back on, the siren is still on. Sometimes a gentle tap on the dash or even pressing the eject button for the tapes and you are back with radio in front and in back (would seem like something loose inside, a wire) until front fades again, with back only working, static picking up progressively up front, and you are in for a new cycle of madness.

Ground problem? Any lead?

I have looked at all cables in back of radio and they all seem to be secure.
On rare occasion everything is fine until I go over a bump.

Which wire, ground could be loose?

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'89 244DL M47 158K miles