2011 6.2 Denali Rear Oil Leak

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jdwood1111

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Hi All,

I did not know if I should add onto a previous thread of mine or start a new one so feel free to merge if mods feel its necessary. Anyway, here is the quick summary that I need some diagnose guidance.

Stats:
2011, 6.2 XL Denali
Bought May 2022 with 92k miles (Range installed almost immediately)
Currently has 96k miles.
Dealer changed oil and trans cooler lines

VERY minor oil leak at the joint between motor trans observed just past dealer warranty. Could not really locate and nothing ever seemed wet I could tell from above. No oil pressure issues.

I added half a quart of ATF to the oil about 300 miles ago before changing the oil in which I used Valvoline full synthetic and a purolater boss filter with half a quart of lucas stabilizer. This was just before I just took the truck to a transmission shop to have the fluid and filter changed. Now after driving the truck (its a second vehicle) I figured I would check the oil leak and it definitely is worse than it was before! It has not dripped onto the driveway but looked like it was about to. Could the the ATF cleaned things out and the synthetic oil is making the leak/seals worse? Something the transmission shop did (how?)?

There still no visible oil I can see from above at all! There is nothing on the passenger side by the starter really. Where I do see the most is on the drivers side through the wheel well at the oil pan gasket and mostly above the oil cooler lines. I assume the gasket was changed by the dealer who changes the lines and it looks like more is above or at the pan gasket. I know there are a few things above there to check but wanted to confirm what and how. The valve cover gaskets do not seem to be leaking at all nor anything from around the VLOM that I can see. Oil pressure sending unit? Rear main I would not think would be on the side like that and inside the cover plate doesn't appear wet but I did not look this evening but will this weekend.

If it may be the ATF and new synthetic oil, is it worth trying lucas stop leak to see if I can undo anything or try locating something else?

Thanks in advance!
 
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Foggy

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It's probably either the oil cooler line gasket at the block or oil filter itself..
It's hard to determine without "seeing" it with the engine running
The atf thing certainly isn't necessary imo... If you are worried about crap in
the engine, just change the oil again right away...
The atf is not good for your VVT or AFM/DOD components as they work strictly from
oil pressure...
The trans shop that serviced your trans would have nothing to do with an engine oil leak.
And hopefully you had them do your trans the right way !!
Drop the pan... Drop the filter... Clean everything up really well... Install new filter...
Clean pan and magnet... Reinstall and fill with with Dex VI fluid
 
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jdwood1111

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The oil cooler lines were replaced recently though but I guess it could be a bad gasket? I see oil along the pan gasket in front of the oil cooler lines though and more above. Ill get some pics this weekend for sure. I probably won’t be doing the ATF again. I did it in hopes of quieting some noise in the motor that others said sounded normal. As for the trans shop, that is exactly what they said they did. I saw some scratches on the trans pan that were not there before and told me the inside of the pan looked great.
 

Geotrash

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The oil cooler lines were replaced recently though but I guess it could be a bad gasket? I see oil along the pan gasket in front of the oil cooler lines though and more above. Ill get some pics this weekend for sure. I probably won’t be doing the ATF again. I did it in hopes of quieting some noise in the motor that others said sounded normal. As for the trans shop, that is exactly what they said they did. I saw some scratches on the trans pan that were not there before and told me the inside of the pan looked great.
Could be the drivers side valve cover of the VLOM (valley pan) plate gasket. Both are common leak points but usually not until higher miles and age.
 

alpha_omega

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Are your motor mounts in good shape or have they been replaced?

I’m not saying this is your problem and I ask because they are often a culprit of multiple oddball things and when replaced those problems clear up. An example being the broken exhaust manifold bolts occur not only because of the poor design of the manifold and the heat, but also get a high amount of pressure added to them when broken motor mounts are ignored.
 
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jdwood1111

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So it has been a while but I do not drive the truck very often so hence the late response. Anyway, bought new oil, filter, oil cooler gasket and RTV to try and see what was going on with my leak. Well, I ended up having to rush the oil change due to family stuff and my leak seems to have stopped. It never looked like it was coming from the oil filter but apparently it was. I have not seen any oil on the inspection cover since the oil change which is where I would see it. One issue down. Then I succefully changed the front pads and rotors today and then bled the brake fluid out. Stops great!

Next up going back to trans which I’ll revisit in my other thread! Just wanted to close this thread out.
 

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