So here's the story. Bare with me. It's going to be a long one. I have an 07' Ford Explorer Sport Trac 4.0L RWD XLT with 155k on it (Currently. When everything started it was 153k). Back in December is when it's issues first started. It threw a wrench light and pulled a P0740 code for either the Transmission/or Trans wiring harness. My mechanics said 99% of the time it's the transmission and not the harness. And also that the labor on the wiring harness can cost just as much as replacing the transmission, if it's the harness that goes inside of the transmission. So we opted to just replace the transmission. They replaced it with a used one with 40k on it that was a one owner (elderly woman) vehicle that was totaled in a rear end collision. It came with all maintenance records and paperwork as well. When they removed my transmission, it was indeed screwed. The front pump was all chewed up and had metal shavings inside. They said they were surprised I hadn't lost any front gears yet. Funny thing is, aside from the wrench light, it really wasn't acting up at all. The light was really my only indication. It hadn't started going into Limp Home Mode or been unreliable or unsafe in any way. If it weren't for the fact that I have a close relationship with my mechanics and they took pictures of the old trans, I would feel like I got played and replaced it for no reason. But clearly it was only a matter of time.

So since then, it has been one thing after another. Different systems/components/etc failing one after another. Going into LHM constantly. Basically unreliable and dangerous to drive. It drove ok for about a month after replacing the transmission, and then it all just went to shit.

After the transmission, my entire cooling system went out. Starting with the thermostat/tstat housing, and the radiator (which was only 3 years old). So all of that was replaced. It was also overdue for a tune up, so the spark plugs were replaced with iridium plugs during this time, as well. Then the water pump went out a week or two later (my timeline is all messed up since this has been going on for so long). So that was replaced, too.

My boyfriend and I took it on a trip up to the mountains (about 2 hours away) for the weekend shortly after and it did pretty good. No major problems. During that time we took it on a pretty rough gravel trail 6mi down a mountain to hike with the dogs and see a waterfall. I was as easy as I could be with it, being that it's a RWD and not meant for that kind of thing. Of course in town, on the way back to our cabin, I was going about 30-40 and ramped a speed hump (that neither of us saw). The impact made me cringe and I of course knew I probably messed something up. It was fine for the rest of trip and for a while after getting back home to/from work and regular driving. With the exception of my allignment and the THREE wheel bearings that were now bad (my fault, so not relevant to the story).

So a few weeks to a month later after that trip is when it starts intermittently going into LHM. As I said, my timeline is a little fuzzy, and I can't remember at this point how many times, or when the first time was. But right before cutting everything (engine power, power steering), either the wrench, check engine, or both together, lights come on. It always happens within the first few minutes of driving, and at this point I didn't trust it on the highway, so it was always at speeds under 55mph. It had also been driving weird, which when you drive a vehicle daily for 8 years you notice the more subtle things. For example, it felt like the engine was literally fighting against accelerating when I pushed the peddle down. There was a very subtle pressure. I could just "feel" that something was not right. Like it was always a hair away from cutting power and going into LHM. The RPM needle was also all over the place. Spiking when not accelerating, and dropping when at a steady speed and not decelerating. That and while in idle, at a stop light, parked, etc., It was shaky. The whole vehicle shook and rattled (not motor mount rattle), but it felt like it was coming from under the vehicle and went all the way to the back. The whole vehicle shook. It felt like I was driving a diesel. Then one time leaving work after it had been sitting for 8 hours, the engine wouldn't turn over. It took me about 5 mins to get it to turn over and start so I could leave. And the check engine light was on. It was 7pm, so my shop was closed. So I stopped at an advanced Auto just to get the code read on my way home. This time it pulled a P0191 code. For the fuel rail pressure sensor. The next day I took it to my shop, we hooked it up to the big scanner, they looked at the readings, and the fuel pressure was definitely not right. The sync of the 02 sensors in bank 1 and 2 were also off. So I left it there they looked over everything, and found that the fuel pump had a pin hole in one of the intake lines. So they replaced the fuel pump as well as the fuel filter. As well as one or two other things. I can't even remember now, and all the stuff he told me kind of went over my head, honestly.

So I get the vehicle back, drive it to/from work for about a week. It was driving great. Zippy, fast, responsive. No problems. I really thought this was the end of it and that it was really fixed for good this time. Until one day, on the HWY (I had finally trusted it again) on my way to work, going 80mph in the fast lane, it completely out of nowhere goes into LHM, no warnings or indications of any problems before hand, it drops to 30mph, cuts power steering, and the wrench and check engine lights come on. So I pull off, turn it off and back on, wrench light is still there, so I cut it off and back on a couple more times, no lights. So I got back on the HWY, made it to work, get off 8 hours later, and it doesn't want to turn over. Takes me about 5 minutes to get it started, so I make my way to leave the parking lot, pull out, and it completely dies IN THE MIDDLE OF THE ROAD. Not just LHM loss of power. It came up with both lights and then completely died. So I put it in neutral, rolled back into our parking lot, and turned it off and back on again until the wrench light was gone. It's 7pm, so again I stopped at Advanced Auto to get the code read (it made it without going into LHM or dying again). This time it pulls both the transmission code (which I forgot to mention it has been pulling off and on since it was replaced) AND the fuel rail pressure code again.

So the next day I drop it off, and he takes off the Throttle body, which he just went ahead and replaced the last time, thinking it may be gunked up and dirty, since he got it from the junk yard. Thinking that may be causing some of the issues and that it may not be opening/closing properly. So it wasn't that dirty, but he cleaned it out anyway. Putting it back on, he notices that the wiring harness to it was missing the plastic coating on all the wires. So going over bumps and the wires touching could have been causing shorts and causing it to go into LHM and causing all of my issues. He asked me if we lived near woods,yet because it looked almost like vermin damage from chewing. I said yes but I park in the garage. He said that they could still be taking up home in my car and that it's not impossible, but it could also be from heat since the wiring harness sits in an area that can get very hot. So he got some electrical tape, wrapped the shit out of all of them, told me to drive it for a couple days and if it does it again we'll go from there. Of course it wasn't that simple. It did it again. So back to the shop it goes. Their original plan was to just go ahead and replace the transmission again. Since it keeps repeately pulling the code again even after it's cleared, and it's under warranty, so it won't cost either of us anything. That, and we're all at a loss at this point on what else to do and where else to go. They have no idea whats wrong with it, and they're just as fed up with it at this point as I am.

So fast forward a couple days after leaving it there. Low and behold, my bf sees a fucking mouse in the garage. It scurried across the wall ON MY SIDE of the garage. Of course days after my mechanic telling me that it was a possiblity. We had no idea. So I call them and ask if they just did a quick once over of everything, or a thorough check of all the wiring. He said he really just glanced, and was getting ready to pull the transmission. So I gave him this new information, about the mice, he decided to hold off on pulling the transmission until he looked more thorougly, and found two wiring harnesses that go directly to the transmission, one to the TCM (which is what it keeps pulling a code for), that had been (presumably) chewed. So he's working on fixing those now, and making sure there's not more. I don't know if we're still going ahead with replacing the transmission.

So what would your professional advice be? Do you think it's possible that all of the codes and everything that's been going on with it are from vermin damage? Or that it may be coincidental, and a mix between the mice damage and actual failure? Do you think we should still go ahead with replacing the transmission, and/or other things? Is there anything we haven't tried or replaced yet? I am so done with this vehicle at this point. I haven't had a reliable vehicle in months and at this point with all the money in it I'm just ready for it to be fixed for good this time, so that I can go back to enjoying it again and not regretting it's entire existence anymore..

I inserted pictures of the vehicle, most of the codes it's pulled over the months, and the chewed up original transmission (before it was replaced) for reference:

*** There is no TL;DR, as I would not be able to outline the full scope of all of the issues properly by shortening everything. If you don't want to read it all, just skip over it. Thank you.

Thank you in advance for everyone's insight and advice! ☺️