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HELP! Transmission fluid leaking on my 3.7 V6

40K views 22 replies 9 participants last post by  Big Blue 
#1 ·
Hi, I have done plenty of research on this. I have the 3.7 V6 (2x2) 2006 Jeep commander. I guess I have the Mercedes W5A580/NAG1 non-dipstick tranny. I am getting a pretty good puddle of leak while the Jeep just sits in the garage.

Just by looking at the bottom it looks like the pan is the one leaking. However, I read that there is a TSB about the electrical connector/o-ring that is the most common cause of leak on these cars. The problem is, I looked everywhere and cannot find this electrical connector! Does my tranny really have this electrical connector?

If it is the pan, I read that this particular pan does not have a gasket but uses RTV instead. Is this true?

Finally, I know this does not have a dipstick but it does have a tube with a cap on it in the engine bay (says for dealer use). If I want to put some ATF fluid in the tranny, can I use this tube? Also, aside from the dealer where can I get "ATF-4"? Autozone? Pep Boys?







 
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#2 · (Edited)
Sorry, probably your biggest question, about an electrical connector seal, I can't answer it, but for the others, to at least help you along.
If it is the pan, I read that this particular pan does not have a gasket but uses RTV instead. Is this true?
No the pan has a big fitted gasket that goes over the edge a round/rolled lip. If the gasket is the source of the leak, replace it, might as well do a filter/fluid change while you are at it, and get a filter/gasket kit.

Having changed the fluid myself, my guess is the lip of the pan is rolled, i.e. has a rounded edge, NOT a flat flang, thus NOT a lot of sealing area for the RTV. I think you would be far more likely to get leaks using RTV instead of replacing the gasket.
Finally, I know this does not have a dipstick but it does have a tube with a cap on it in the engine bay (says for dealer use). If I want to put some ATF fluid in the tranny, can I use this tube? Also, aside from the dealer where can I get "ATF-4"? Autozone? Pep Boys?
Yes, you add fluid by twisting off the cap on top of that tube and pouring ATF+4 down it using a trans funnel. You also put the special tool dipstick down it to check the fluid level.

This tranny is very sensitive to overfill, that is why it does NOT come with a dipstick and says only the dealer should service it. So I wouldn't add fluid without knowing how much is needed.

It is possible to check the W5A580/NAG1 fluid level yourself, but you need the special tool dipstick (got mine off ebay), a way to measure the fluid temp (the dealer uses the starscan tool to read the temp sensor, I use a trans temp gauge I installed) and the table to show the exact fluid level vs temperature (downloadable off the internet). The dipstick is NOT easy to work with, it is NOT hard at all to dip it incorrectly and get the wrong fluid level reading.
Also, aside from the dealer where can I get "ATF-4"? Autozone? Pep Boys?
ATF+4 is licensed by Chrysler, an oil manufacturer has to pass Chrysler's specs to be allowed to use the name "ATF+4" on the bottle. So as long as it has "ATF+4" as the name on the bottle, you would be fine. Don't confuse that with the small print on the back of the bottle saying the oil companies "claim" it can be used in "ATF+4" applications. If the name of the fluid is NOT "ATF+4" on the bottle, it is NOT ATF+4 and you should NOT use it.

I've seen ATF+4 sold just about everywhere that sells transmission fluid, including walmart that has it as its own generic brand, as well as others.

NOTE: Some of the more specialized synthetic companies (AMSOIL, Redline, Royal Purple, Mobil1) do sell a Synthetic ATF they claim will meet the specs for ATF+4, but NOT exactly thus they can't claim it is ATF+4, and from what I can tell, they do work well. BUT, for warranty purposes, they are NOT ATF+4 and no argument in the world about how the fluid is better quality is NOT going to amount to a hill of beans if a warranty is denied for using the "wrong fluid".
 
#3 ·
I havent been under a Mercedes trans for quite a while so....the connector is just above the bottom edge of the trans, above where the pan meets the case......it is the only connector.
When it leaks, it tracks around the edge of the pan, making it appear the pan is leaking.

Look harder...it's about the diameter of a nickel.

Rob
 
#6 · (Edited)
Is this what I am looking for:


I spent 30 mins under the Jeep with a flashlight looking for such a thing and can't find it. I even removed a heat shield held with two 10mm bolts thinking it would be under there but it isn't. I will have to go under it one more time to check harder. In the meantime, is there a diagram online to actually see this particular tranny?
 
#4 ·
The o-rings to the wiring harness went bad on mine also, creating e leak. The fix was simple, although I didn't do it. This is located to the forward of the tranny, don't remember left or right side though. One of the front corner bolts that holds the pan in place also holds a guard plate that kind of covers, protects the harness. Once the bolt and guard plate are removed, you'll see the wires going into a large plastic lug, I'll bet this is your leak.
There's a Utube video replacing the valve body on the NAG1. In this video he shows how the harness is removed and reinstalled. If I would've seen the video before the leak, I'd have done the repair in my driveway. And As Mongo stated, there is definately a heavy rubber gasket to the pan, and I'm told this hardly ever goes bad. Good luck!
 
#9 ·
It appears you have photographed the connector we are discussing......if so, that leak rate should be a tow truck ride to a trans shop.

It appears there is another source of leakage above the connector......maybe a fully failed cooler line.

When the connector leaks, it is a occasional drip and it wicks along the edge of the trans pan, never a steady stream like I see.

If this is going to be a DIY event, start by flooding it with brake clean spray and let it dry off.....fluid won't leak uphill so you can better identify the leak source.

Based on what I see I'm really thinking cooler line failure as the primary leak.

Rob
 
#11 ·
Oh my..I apologize for being unclear on my posting. The first post of mine with pictures are the actual transmission pan on my commander. The following posts are NOT pictures of my car. They are pictures I found on the internet. The point I was making is that I CANNOT locate this so-called round "Electrical" connector on the transmission. I posted those pictures from the internet asking if those are the same connectors I need to look for on my Jeep.. Sorry!
 
#10 ·
I agree with Robby, it looks like the cooler line bolted into the tranny just above that point is leaking, and leaking pretty badly.

If I "remember" correctly the driver side cooler line is pressure/out, the passenger side line is return.

They use this new kind of funky connector that has a big rubber bushing between the fitting and line, if I "remember" correctly the rubber bushing is just about flush with the nut/fitting. In your pick the rubber bushing extends quite a bit from the nut/fitting. Compare it with the fittings on the other line, if that rubber bushing is pulled out farther then it should, I suspect that is the cause of the leak (no I doubt just pushing it back in without removing the nut will stop the leak totally).

I don't have enough experience/knowledge about these fittings, if it can be taken apart and have that bushing forced back in to seal it up, if you can replace the fittings on the end of the line or if you have to replace the entire line as an assembly. Eitherway, I've seen posts about folks working on these line, and from appearance, it really looks like it is a DIY job for most.

The problem will be topping off the trans to correctl level, like I said, you'll need:
  • The special tool dipstick
  • A way to measure the trans fluid temp
  • The table for fluid level vs temp
BTW, you're guessing when you say half a cup low, half a cup low is NOT going to hurt the trans, while a whole cup high 'might' hurt the trans. I would avoid adding fluid unless you have a way to determine the fluid level is correct. The tranny fluid level is NOT something you want to guess with, especially this trans.
 
#12 ·
I fought this problem (or similar) for over a year until I finally got the right mec to rack it and discover one of the seals leaking on the wiring harness. It never leaked when hot, just after sitting over the weekend with out being moved. damnedest thing. $180 later and a new harness and no more leaks in the drive way for over a year now.
 
#14 ·
Yes! When I leave the commander in the garage and not driven for a couple of days, there is a big leak underneath. When driving however, it doesn't even leak that much. Can you be specific on where it was leaking on the harness? Is it the pictures I posted earlier?
 
#15 ·
I haven't done the job, take this with a grain of salt, but its pretty clear to me from the pics there is two places for the wire harness to leak. Between the wires running through the plug or around the seal between the opening in the aluminum trans case and the plug that goes with the wires running through it, that goes into the opening.

Like any leak, clean the area thoroughly to remove all the leak fluid and then keep going back and checking the area to try to catch the leak as it first starts. With a fresh clean area, you see where the point is that the leak starts at and be able to narrow it down.

It might require a whole new wire harness or it might just need a new seal between the harness and the opening in the trans body. There looks to be a threaded plastic collar around the wire harness, it might be worth it to try to tighten it and see if that solves the leak.
 
#17 · (Edited)
This is our tranny, WAtch the first minute of the video. :bouncy:

From the video, it appears potential leaks for the wire harness are:
  • The Plug is Loose - the collar that locks it in has turned and loosened (simply tighten the collar and relock the connector back in).
  • The Harness itself - the oil is permeating the plug and coming out around the wires coming out of the plug (replace the wire harness, should just have to unlock it and pull it and put in the new one and lock it, make the connections on the other end of course).
  • The Seal for the Plug in the Harness - what ever seal is used between the plug and that connector, looks like O-rings, might have gone bad, if you can get the seals for that plug on the harness you may NOT have to get a whole new harness).
  • The O-Rings - the connector that bolts in, O-rings have started to leak (Remove the connector and replace the o-rings, shouldn't have to drop the pan or valve body to do it).
  • The connector mounted in the trans - the connector body has cracked or warped (shouldn't have to drop the pan or valve body, just unbolt the connector like the video and replace it with new and new o-rings).
 
#18 ·
Sure, any of the above are likely. Although the tech the repaired mine said that the o-rings are a common failure. The video was sent to clarify the harness in question and how simple to disconnect and hopefully repair.
I'm wondering how many transmissions are actually rebuild when replacing faulty valve bodies would have solved many problems! Something to think about.
 
#19 ·
Sure, any of the above are likely. Although the tech the repaired mine said that the o-rings are a common failure. The video was sent to clarify the harness in question and how simple to disconnect and hopefully repair.
Yea, I would think that is the most likely scenario. First I would check that lock ring and make sure it is locked down tight, if its loose that could be the source of the leak and the solution would just be to tighten it. Then I would replace the O-ring on the wire harness. If it was still leaking, I'd move on to other potentials.

Remember, unless instructions say otherwise, lube O-Rings before inserting them, i.e. rub a little ATF+4 over them.
 
#23 ·
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#22 ·
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