Rubber bung?

A little bit more info on the picture:

Bottom is towards the front/engine and the top of the picture goes toward the rear/transmission.

That the service slot plug on the back of the engine. You remove it to gain access to the flywheel / torque convertor bolts.
If it's ATF the torque convertor is leaking. If it's engine oil the rear main seal is leaking (most likely).

Any experience with it? Anything special I need to do to make it fit properly or is there a small chance that someone put a wrong size one in there?

Thanks for the help!

I believe I've read as said above its an inspection plug. It most likely has nothing to do with your oil leak. Looks as though the oil is coming from further up front and splashing back there.

Interesting point. I guess I need to delve further. I just figured it was the slot plug (thanks for giving that term, now I can do a fruitful internet search) since the leak is so slow that even having it parked for a week at a time, there is no drip on the ground.

The picture might be a little deceptive because only that corner of that pan has oil as if it is leaking out of the corner of the inspection hole (i do park on an incline in my garage so it could drip in a direction). But again, I gotta do some more research.

I've updated the diagram... The previous one was incorrect.

It's the window to remove the torque convertor. If you have red fluid the torque convertor is likely leaking, if the fluid is dark brown to black it is likely the rear main engine seal leaking.

Just confirmed its black oil.

I would re-torque all the oil pan bolts and pressure clean under the engine area.

Thanks for all your help guys! Luckily I bought an extended service plan with this truck, if it does hit the fan.

I will do as suggested above, might end up just taking it to a mechanic.

ddaaccee said:

Hey guys, first post.

I was poking around under my truck and I noticed some oil under the engine and transmission. It pretty much centered around this rubber bung that I have no idea what is called. I pulled it out, put it back in trying to make it fit better. No luck. You guys have any idea? I'm obviously losing some fluid, which can't be good.

Click to expand...

What's the rubber plug called

Plug, oil pan hole. GM PN 12569419. Gm has discontinued production, but maybe Google or Ebay can find one.

Hello,
I know I'm YEARS late. But did you take your hummer to the mechanic? What did they find out? I'm sorry if it was answered and I missed it but I'm actually under my hummer h3 right now with the same concerns. Any help would be much appreciated.

Thanks,