Leaking Transmission Lines, safe to drive?

So I've recently noticed the lower of the two transmission cooler lines has a perpetual drop of transmission fluid that seems to hang there. Due to the sealed nature of the 4.0l auto trans and the fact that my truck just recently got blasted with woolwax makes crawling underneath and going through this heinous trans fluid check procedure every morning something i'm just not willing to do.

I'm unfamiliar with how exactly this lower line functions and why there is never any detectable drop of fluid on the pavement underneath the truck, yet always one hanging on the line. I have it scheduled to go in the shop and get repaired in 2 weeks but wondering if someone who knows more than me could explain when during normal operation fluid might be more likely to leak from this line? wondering if am I pissing it out as I go down the road or, assuming there is no puddle under the truck in the morning, the transmission is quiet, shifting normal, and no codes are thrown is it safe to assume I havn't lost much fluid and ok to drive? Would the trans temp light, or CEL come on prior to any major damage being caused if I was in fact low on fluid? thanks in advance

 

Is it leaking towards the front, i.e. basically under the radiator? Most likely location would be the transition from the hard lines to the soft lines leading to the tranny cooler. If you can isolate it to that junction make sure the hard lines is pushed far enough into the soft line. Consider replacing the clamp, adding a second clamp or using a different style mechanical clamp.
That you are not dripping likely means you have not lost that much fluid, but you really never know without checking. Get the leak stopped then read up on how to check the tranny fluid level. If it is shifting fine at present I would not sweat the level too much... The truck doesn't have much in the way of self protection indication for low level, no CEL etc. First thing you are likely to notice is shifting issues, which most likely indicates level issues as opposed to any damage.

 

I think the lower line feeds the ATF cooler. The line goes into a rubber hose at the front of the truck. Under the skid plate. You might check to see if the leak is originating there.

 

I'll take another look but I'm fairly certain It is leaking from the hard line near the coupling area where it threads into the transmission, the lines are rusty.
This picture is from another thread, not my truck, but almost exactly the same thing going on here:

 

Keep in mind ATF is very combustible at a rather low temp - ~300*f

 

That’s great that you recently applied woolwax, but it was to late to correct your present problem. You have corrosion, and corrosion eats metal/ aluminum. As the corrosion eats away the metal, the tubing will gradually lose its circumference and small leaks will appear. You need to replace the part.

 

Mine are in good shape at those locations but when I added rust treatments I sprayed those fittings for future removal. It appears the coating on the lines is bubbling up from the line. Time to replace. Remember going down the road those lines are pressurized. How much I'm not sure.

 

Ok I think we are straying away from the questions posed in my original post. No, I am not under the assumption woolwax will somehow repair rusted transmission lines. The mention of woolwax was purely to illustrate how crawling under my truck and checking the fluid level is an extremely messy/unpleasant process. I am already having the lines replaced in 2 weeks also as previously stated. MY questions are centered around the function of the line in question (I.E. is it pressurized only while hot/driving) and the risk of causing damage to a potentially underfilled transmission due to such a leak, basically if I should drive it or not.

 

I was not implying what you said. The short answer is your leaks are probably from corrosion. Since your getting them replaced in 2 weeks , how much much have you lost ?? If you don’t know,than maybe you shouldn’t drive it. If it’s less than a qt. no problem.

Wool wax on a frame doesn’t make it to messy to check. Just check it if your able.

 

No, those line aren't under any "significant" pressure beyond what it takes to circulate fluid at a reasonable rate. People routinely report running these transmissions short a quart or two before experiencing any shifting issues. That said you won't know what you have till you check... If it were me, and the trans was shifting fine, I would drive it without hesitation. Good that you are getting the lines replaced. Not a bad job if you are inclined to do such things yourself.

 

The factory hardlines are not super expensive. I recently had leaking lines due to corrosion, and replaced them with stainless braided hose as part of a cooling loop overhaul, and the fittings with appropriate adapters for the 6AN fittings I used for the hose. I did, as a temporary fix while waiting for parts, use some original formula JB Weld over the pinholes and it was good for much longer than I thought it would be.

If you're going to DIY, I would recommend planning on replacing the fittings on the transmission case - on my truck, they were corroded to shit and I had to cut the hardlines for clearance and then back them out of the transmission for replacement. It was when I discovered that issue that I decided to go with stainless hose so that I could also eliminate the small section of hardline towards the front of the truck, where it transitions from hard line -> rubber -> hardline -> rubber -> cooler.

This post and the next 3 or 4 from me following it have some pics of the carnage/install:
https://www.tacomaworld.com/threads/new-england-b-s-thread.204874/page-9533#post-27726660

I believe I still have a complete set of OEM trans case fittings, hard lines (minus the front hard lines), washers, etcetera new in box if you need them.

 

About a couple months ago I descaled and "painted" the undercarriage of my 2014 Tacoma with Fluid Film. I always try to pay attention to the condition of undercarriage components when doing this kind of stuff. I didn't see anything leaking on or around the transmission. A couple weeks ago I was about 1.5 hrs from home and all of a sudden the AT wouldn't shift from 4-5, no CEL or any other lights. I pulled over to "reset" and took off. Still wouldn't shift from 4-5. Tried the "reset" again for a few minutes and took off, as we were a few miles from our destination. I did see the A/T Temp light flicker on/off. By the time we got to our destination shifting was a greater problem and it seemed like the clutch wouldn't grab. Not good! I called my mechanic brother in-law, he suggested NOT driving it, so I got it towed back home (90 Miles) to the Toyota shop. They said one of the cooler tubes had rusted through and it was low on fluid. They replaced the cooler tubes, did a flush. Now the clutch engages but the transmission is slipping big time in the middle gears on up. They said the transmission is toast. I'm presently waiting for a replacement with 65,000 miles and a 12/12 warranty. I've been advised by friends who are into cars to go with "used" transmission vs a rebuilt.

I'm posting this as a warning to be very careful! There isn't much space between "fixable" by adding fluid and "toast" where it needs to be replaced. Its a very thin margin, at least in my experience. I don't understand how I can go from not leaking to leaking bad enough to damage the transmission in such a short duration?!? Also miffed with Toyota that those tubes are not stainless steel and that there isn't a dipstick!

 

I'm not the most knowledgeable one in the group but my recommendation is to maybe put a cup or something to catch fluid underneath the area and take it for a test drive. Once you know how it "spits out" you could get a better idea on how much you've been loosing on the roads. Personally I'd park it as often as possible till your appointment but obviously everyone's needs are different. Hope it goes well for you in the next couple weeks! Keep us posted.

 

If you are the slightest bit concerned, don’t drive it until the fix. Burning up your transmission from low fluid isn’t worth the risk for how expensive that fox will be.