Electrical? Transmission? Help!

[Dtxand1]

I'm hoping someone can help me. I have an 03 ex 4.0 I've had for a little over a year. It sat for 2 years because of a gas leak they couldn't or didn't want to fix. We put a battery on it and drove it home with no problem except gas leak and door ajar light on. And a new fuel pump fixed the gas leak. The door ajar I felt was no problem.
I've drove this truck all over Texas with no problem. A couple of months ago it started shifting hard into reverse. Then we noticed it wasn't shifting smoothly in drive. Sometimes it works great sometimes not. Then about a week ago after being on the highway for about an hour 70 to 85 mph. my voltage gauge on dash went all the way to the H, overcharging, door ajar light went off airbag light came on, radio went off, windows wouldn't work. After it sat for a couple of hours gauge went back to normal everything worked. Driven it twice since. Everything starts out great but after 10 miles or so it all happens again. Transmission shop says tranny is good (I don't know they actually checked it out). We've checked fuses. We've set in driveway trying to replicate the overcharge and nothing. But when I'm driving the gauge goes up and assessor's go off. Battery is 12.7v not running 14.7v running. Having truck running turning things on one at a time lights, a/c, radio etc. the battery stays at 14.7.
Could my transmission cause electric malfunction?
Alternator?
Voltage regulator?
A stupid sensor somewhere? Also someone put Kenwood system in with amp.
We just need to be pointed in right direction. Thank you sorry for the long post.

 

[Number4]

The 02/03 are more susceptible to broken ground wires in the drivers door jamb. And broken positive as well. When the door is closed, and the vehicle moving, it’s possible that these broken wires can make contact for a period of time.
You’ll find discussions and how to’s if you search.

basically, you need to pull the jamb dust boot out of the door and tug on each wire. Then tug again. Once you find it, you’ll need to splice in a 2-3” length of wire to fix it.

At least check this out as it impacts the door ajar (which will also drain your battery) as well as the dash/radio.

here’s a link that will help.