Puddle Under Your Car or Truck How to Diagnose Transmission Leaks

What now? Transmission fluid.

Hey friends, it's Len here from 1A Auto. Today, we wanted to talk to you about transmission issues, specifically a transmission-fluid leak. Firstly, we're gonna start off talking about symptoms. Some of the symptoms that you might notice is maybe you just started your vehicle, you go to go from park, maybe to reverse or even drive, and it takes a second. And then...and it kind of goes. Or maybe you go to go into reverse and you step on the accelerator, you can hear the engine rev up but the vehicle just isn't moving. This is gonna be very common in reverse especially and I'll get to the reason why in a second.

Also, you might notice, when you're driving down the road and you're accelerating up a hill, you go to hit that accelerator pedal once again. The vehicle is just not accelerating to match the amount of RPMs, or revolutions, as you're trying to drive. Right? You're trying to accelerate and the vehicle's just not moving fast enough. There's gonna be a couple other symptoms that you might notice but these are just some of the basics. Essentially, what these are probably gonna come down to and the more than likely reason would be a transmission-fluid leak.

So, now one of the first things in the diagnosing process is of course safety. We're gonna think about eye protection and hand protection because we're gonna be dealing with a chemical, ATF or transmission fluid. But that said, you wanna get underneath the hood of your vehicle and you want your vehicle to already be at running temperature or operating temperature. So, essentially, go for a ride, go get an ice cream, come home, park on a level surface. While the vehicle is still running, go ahead and pop your hood. And then, you're gonna try to find your transmission dipstick or even check the fill plug.

Now, some vehicles you're gonna have a clear transmission dipstick. Generally, it's gonna be in red, which signifies transmission fluid. And if you saw the yellow, that's gonna signify oil, so we won't worry about that today. Anyway, go ahead and grab on to that red transmission dipstick. And if you're dealing with a plug, it'll probably have a red cap, and sometimes even black. But anyway, grab on to it, draw it right out, and we're just gonna wipe it right down. While I have it cleaned off, I'm gonna show you what we're gonna look for.

So, now, looking at the dipstick, you see the end. And then, if you were to come up, you're gonna see an area with two dots and some hatches in between. When your vehicle is warm and running and on a level surface, your transmission fluid should be in between these dots, preferably closer to the top one up here. When your vehicle is warm, you definitely don't want your transmission fluid up here, up here, or even worse...I don't know, not even on here. If you pull out your transmission dipstick and it looks like this with the vehicle running, your transmission fluid is super low.

Now, with all that said, we know exactly where we want the transmission fluid level to be when the vehicle is running, like I said. We're gonna go ahead and reinsert the dipstick...pull it back out.

All right. So, we got the transmission dipstick out of here and we're looking to see where our fluid level is. As you can tell, I don't see any fluid in my safe range there. As I move my way down, I can see that there might be a minute amount of fluid right here but it's very minimal, if anything, which tells me that that's probably not even the level. And then, down here, it's extra thick, which tells me that that's probably approximately where the level is. If the fluids down here, and it should be up there with the engine running and hot and on a level surface, obviously, you're gonna notice some of the symptoms that I talked about earlier.

So, now let's go with the assumption that you checked your transmission fluid while it was running on a level surface and you found that that fluid was low. Why would the fluid be low? It would be low more than likely because you have an external fluid leak. The reason why I say external is because you should be able to kind of maybe visibly see it, possibly by a drip on the ground or even accumulation of moisture and even debris at such point.

So, let's go over some of the common places that I would look if I was looking for said transmission-fluid leak. Let's take a look under the vehicle to see if we see any leaks.

All right, I can see a nice puddle on the ground over there. That kind of tells me approximately where I should start looking but I'm not gonna rule anything out just by that. Now, if we were going with the assumption that you found the leak towards the front of the vehicle, some of the places in the front I would look would be maybe along the radiator. A lot of times, on your radiator, you'll notice that you have transmission cooler lines that run into it. If you were to look along those transmission cooler lines, you might notice an accumulation of debris like this, which kind of tells me that this might be seeping. And as you would move further down, maybe you'd see some even further accumulation. That just says that it's a pretty good seat.

A lot of times, if you look behind your grille, you might see a transmission cooler that looks like this. That would have those transmission lines going into it as well.

On a side note, if the symptom only happens to be you're seeing transmission fluid on the ground but you don't see a transmission-fluid leak in any of the common areas, it could potentially be your power steering fluid. Some models of vehicles actually recommend using transmission fluid in their power steering system.

Now, if we look behind this plate, you'd be able to see those transmission lines. They come down this way and they're gonna run right on over to the transmission.

Just a quick note, if you happen to have an external transmission cooler, you're not gonna have two lines, you'll more than likely have three.

Follow those lines right to the transmission, check where they go in. These look good.

Another place that might leak would be your transmission pan gasket. That's the gasket that goes between the pan and the transmission itself. But, if you happen to see that you have transmission fluid around the pan, don't let that make you think that it has to be the transmission pan gasket. You also wanna look above it because, well, gravity works. If you have a transmission leak that's located above the transmission pan gasket, the fluid will of course run down, and then, run along the pan and kind of give you the symptom that it's a pan gasket issue where really it might not even be. If you have an automatic transmission that's gonna have a selector shaft like this, that means it's also gonna have a seal that has to be there that leads into the transmission. If the seal's bad, you'll have a leak.

On rear-wheel drive vehicles, your transmission's gonna have an input seal, which is the seal that's gonna be in between the engine and the transmission. And it's gonna have an output seal which would be the seal that goes between the transmission and the transfer case or the transmission and the rear drive shaft.

Up towards the front of the transmission, inside this area right here, which will be considered your bell housing, is gonna be where the torque converter is. If you have a leak, it's gonna be up inside this area and it's gonna come leaking down on the inside of this area. Generally, you'll have some little covers that they put on here for you, we'll call them check covers. You can go ahead and pop those out. And take a peek. If it looks like fluid comes pouring out and it's reddish, more than likely it's transmission fluid.

Moving down the transmission to the rear, in our application, we have a transfer case. But let's say you don't. You would have an area that's gonna look like this, we'll call it a tail shaft, you'll have a tail-shaft seal which then leads to the rear drive shaft. This seal right here tends to leak. If it does, you'll probably usually see it coming out of that weep hole right there, or maybe even around here, causing a mess.

You might also have a leak between your transmission and your transfer case, assuming you have a four-wheel drive drive shaft system. If that's the case, you'll probably see it somewhere along a seal that looks like this. It's just kind of accumulating a lot of gunk. That means that it's got moisture and that's, of course, accumulating the dirt.

Maybe you don't see an apparent leak in any of these places that I've mentioned but you have a four-wheel drive system and the fluid still goes low. Where's the transmission fluid going? A common place, in GM trucks especially, would be if you were to pull out your transfer-case fill plug right here, you don't wanna stand back because fluid's gonna come spraying right out of there, practically under pressure almost because it's gonna be so full. The reason for that is because the internal seal, between the transmission and the transfer case, is no good. When you drive, your transmission-fluid pump is pumping fluid under pressure and it's forcing it between the seal and between the transmission and the transfer case and it's slowly, over time, filling up that transfer case.

Now, switching over to cars, if you were to have a front-wheel drive vehicle, your transmission might look a little bit different. Maybe it doesn't have a transmission pan that's on the bottom. Some of them do, some of them don't. You might also find a transmission pan on the front or even maybe one of the sides. Other areas that a transmission might leak is along any of the seals in between the case of course. And then, of course, you'll have the areas where your axle goes in to the transmission right along here. Any place that something goes into or out of the transmission has to have a seal. So check around those axles, make sure they're not wet. And, of course, check all those usual places, such as lines and coolers and radiator and all that.

Okay, friends, so we tried to make an educational video for you showing you some of the common areas that you can look for are transmission-fluid leak. Hopefully, you found that leak. Next thing I would do is go right to 1aauto.com and check to see if we have the parts to get it fixed for ya.

Real quick before you go, it's super important to make sure that you fix that transmission-fluid leak ASAP. The last thing you wanna be doing is polluting the environment.

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