Transmission Fluid Slow Drip (2012) Question

I have a slow leak on the passenger side of my Tacoma. I’m pretty sure it’s transmission fluid as my other fluid levels haven’t changed and intermittent gear shifting issues went away for a while after I topped up the ATF system. But those issues returned very gradually and I started noticing a leak basically right under the passenger seat. I can’t figure out where the leak might be originating from though, I’ve attached some pictures and was hoping someone might have an idea where it might be coming from if they’ve had similar issues.

 

That's some nasty rust. Just a guess. If it's an automatic I'd look at the to/from line to the radiator.
With the rust I'm seeing, you may have other problems you're not seeing.

 

That looks like the engine room on a Tug boat.

 

The transmission lines run right along that side, just get under the passenger side and follow them with your hand, I’m guessing you have a pinhole leak in the hard section before it turns to rubber.

 

Agree with the previous folks in previous responses: Seeing the extent of the rust, the first thing I would scrutinize is the metal transmission fluid lines, especially the ones to the auxiliary cooler (if equipped) and the lines to/from the radiator in-tank cooler.

If they get corroded enough, the metal lines will seep fluid right through the rusty line. If it gets bad enough and one of the pipes cracks, you'll have a catastrophic failure in minutes.

 

Ok solid, that makes sense. I'll get under the truck again and try to find that leak. I (obviously) live in a high-salt province (newfoundland) so rust is a given - would it be beneficial to swap those lines out for a rubber hose or just stick with the OEM system and order and install new metal lines (that will probably rust out again eventually)?

 

You could run rubber lines from the trans out.. Judy be really careful on your routings.. you could cut the hard lines closer to the transmission where it shouldn’t be as rusted, put a slight flare on the ends to hold the hydraulic oil approved rubber lines in place

 

Just an update in case anyone finds this thread. This thread was super useful in helping me figure out what I needed: https://www.tacomaworld.com/threads/how-to-replace-rusted-transmission-cooler-lines.690165/ and this youtube video was a great resource for figuring out what I needed to do: https://www.youtube.com/watch?v=zbZROM71yyA. If you're in Canada look into ordering from Toyota Parts Direct or Lines To Go to save some money on lines, my local dealership actually price matched TPD for me so I was able to save money and time. The upper line was the main issue for me - it was bubbling from rust which led to a small pinhole leak. I swapped both lines to since I was doing it though. The hardest part was probably removing that top line connection to the actual transmission since it was rusted in place, I was able to saw off the lower line and use a socket to get it off but on the top I could only fit the wrench - it's a pretty tight space to work in. If you're going to be planning to take these off make sure you put some rust remover/lube on the connection a couple days ahead of time to really help yourself when doing this.