Hi, I have a 2015 JKU w/ Auto Trans. 6 mo's ago, I moved to an area with a lot of mountain driving at 45-55 mph. Essentialy any time I drive I am climbing or defending 2000' of elevation.

This week I noticed oil coating the underneath of my transmission and crossmember.

I suspect by reason of deduction it is the oil pan gasket leaking, but I suspect there is an underlying issue caused by the harder driving (excessive pressure) but I'd like help confirming before I buy parts and dig in.

1- Does not appear to be oil coming form the top of the transmission ( I can not see the vent but I dabbed paper towel along the top of the transmission and I don't see oil that amounts to much.
2- I removed the rubber plugs under the bell housing (oil collected there) but NO oil inside... dry.
3- No oil coming from the engine. filter, pan, bell housing, heads, hoses, etc.
4- Oil dripping from the transmission pan bolts and all along the frame crossmember.
5- Oil collected around the flare nuts of the coolant lines but not around the pipe (seems to be residue and not source)
6. doesn't appear to be coming from the transfer case.

It seems cut and dry really, I just haven't had a pan leak before. on this jeep or other rigs.

SPECIFIC QUESTION. I'm looking for another contributing factor of excess pressure... Is it likely my bypass valve to the cooler lines is stuck? Should I replace this? Seems to me this would not only cause higher temps by higher pressure, is this true?
Admittedly I haven't check temp recently, but is there a way to test his without just swapping it? Is there a sensor that monitors transmission pressure or just temp...

Thank you in advance, I am in a position I need to be efficient with this repair and I am essentially looking for validation or a "hey no, check this first" thing.

Lastly, what is the best tranny fluid for my Jeep, for my driving conditions... High heat, high pressure?

Thank you!!
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ATF+4 is the fluid you should be using.

Check fluid level if you have a transmission dipstick. (Transmission warmed up, engine idling, in Park.)

I would clean off all the fluid residue before you make any repairs. That will make it easier to find the source of the leak.

 

Are you the original owner? How many miles? Only asking as I'd suspect lot of jeeps out there aren't getting their tranny fluid changed at intervals. That fluid is likely way darker than what the normal ATF4+ is, but obvioulsy that is a red color vs. motor oil. first step is always to clean real good with degreaser, give it a couple days and then inspect real good. likely going to pinpoint the origin easier that way. if you haven't had that tranmission fluid changed, maybe it's not a terrible time to drop the pan and do a drain/refill anyhow (fun times there) and replace that gasket at that time when reassembling. Pretty straightforward job cept for getting at those rearmost bolts which takes a small bit driver to really access the best.

 

Thanks for the reply guys. I've had this JK for the past 2-1/2 years. I got it at 60K miles and now it's 85K miles. No idea what has been done before I bought it but it was pretty clean.

Alternatively, the tranny fluid is not red. it's more oil like in color. I have a Ford Ranger and it uses a specific Tranny fluid that is not red either. At the moment I don't remember the name.

But that's interesting. I suppose it could be very mild red but it doesn't really present that way.

Yeah I guess maybe cleaning it real good and looking for it again is a good idea. I have yet to check the level but it's on my list.

 

At 85k, it's not a bad time to just drain and refill anyhow. No way a previous owner did it at, or before, 60k. I try to drain and refill mine at 60k interval. Speaking of.....it's that time for me.

Last time I attempted a controlled spill (we have no drain plug), and I didn't opt to install a pan with a drain plug either. This time I will use a mittyvac to get as much out through the dipstick before dropping the pan.

 

Yeah that's a good idea. I'm planning to swap that pan for one made by PPE. It has a drain plug. I installed their oil pan last year and ended up really liking it.

Your probably right. it's probably original which would explain the change in color. It's something on my list but it has been overridden by 100 other projects. This is what happens when that happens

I also plan to replace the bypass valve with a PPE version. The PPE oil pan holds more oil and consequently bigger consequently requiring exhaust spacers.

Fortunately, I really like working on and modding my Jeep!

 

A flat bit driver like this (mentioned above) will help get at those rearmost bolts. I has already relocated my exhaust crossover to behind the crossmember and still had bit of an issue accessing those 2 rear bolts due to the crossmember itself. Little bit driver like that made my life easier. There's not enough clearance between the bolt head and crossmember to get a normal socket wrench in there.

 

Thanks for the tip. I was actually thinking about just removing the cross member... unless it proves to not be worth the hassle. Maybe it won't be.

Truth is I probably need to exercise some restraint so I don't make this an excuse to turn it into bigger project than it needs to be.