Grinding sound

So I've never heard of this happening and everywhere I look I can't find any information.

I turn on my jeep the other night and I put it in drive. (Automatic trans) When I shift into neutral and park it makes a loud grinding sound but it still goes into gear and shifts normal. My first reaction is obviously a transmission issue..
HOWEVER...

Tonight I realized it only does it when I have my headlights on... It also glitches my radio for about 5 seconds.
I figure it's an electrical issue but I don't know where to start when trying to fix this.

04 LJ
Automatic
100k miles


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alternator starting to go? whether electrical or mechanical, a messed up alternator can bring out mysterious demons. autozone and advance can check your alternator. it needs pulled out though for them to hook up the machine.

My TJ absolutely freaked out when the battery was dying. Alt guage showed 14v, but battery itself was shot. That said, the 42rle in my jk makes an interesting solenoid noise when changing into reverse. Perhaps electrical issues are making it sound worse.

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BobNH said:

My TJ absolutely freaked out when the battery was dying. Alt guage showed 14v, but battery itself was shot. That said, the 42rle in my jk makes an interesting solenoid noise when changing into reverse. Perhaps electrical issues are making it sound worse.

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Click to expand...

My tj acted funny with a bad battery as well. It would randomly peg the gauge out at 18v. I thought the regulator in the alternator was going to bad. Swapped out one that i had laying around, same issue. Changed the battery, problem solved. The weird thing is that it never had any starting or driveability issues. As far as the op's issues go, i would lean towards the alternator being as the issue only shows up when he has it under a load.

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holliewood61 said:

My tj acted funny with a bad battery as well. It would randomly peg the gauge out at 18v. I thought the regulator in the alternator was going to bad. Swapped out one that i had laying around, same issue. Changed the battery, problem solved. The weird thing is that it never had any starting or driveability issues. As far as the op's issues go, i would lean towards the alternator being as the issue only shows up when he has it under a load.

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Click to expand...

lol, yep, my gauge did that spike as well. And this strange, almost inaudible "ding" when I pressed the brake pedal.