Help diagnosing oil leak

beastybaconman · Apr 26, 2016

I've had my truck for a while now and it seems like the bottom of the transmission is always wet with oil. It can't be a huge leak because whenever I check the tranny or engine oil it's not really that low. I haven't looked into it too much but anyone have a suggestion on what I should check? It's a NV3500 5 speed tranny and the 5.0 vortec if that helps.

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kennythewelder · Apr 26, 2016

That looks like your rear main seal is leaking. If it is engine oil, and it is coming from in between the trans, and the engine, then that is what is leaking. You have to pull the trans to change it. Here is a video on how to change the seal.

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beastybaconman · Apr 29, 2016

kennythewelder said:
That looks like your rear main seal is leaking. If it is engine oil, and it is coming from in between the trans, and the engine, then that is what is leaking. You have to pull the trans to change it. Here is a video on how to change the seal.
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Thanks for the reply, that's what my dad said it probably was too. It's not too bad for now so I'm just gonna keep a real close eye on the oil level until the next oil change which will be pretty soon, that way I only have to drain the oil once.

kennythewelder · Apr 29, 2016

My truck has had a rear main seal leak for a long time. I have used several products to stop it without doing a teardown. The last thing I used was Blue Devil rear main sealer. It does help. It slowed my leak a lot, but it does still leak a little. My truck is always parked on concrete, at home, so any leak shows. I know the leak will come back slowly, that what it always does. I have never lost even 1/2 quart of oil between oil changes. Now it is a lot less than that. Just remember this, if you use any oil stop leak, it will expand all of your seals. Anything that is rubber will be effected some what. Here is a link.

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Help diagnosing oil leak

beastybaconman

Newbie

kennythewelder

Officially Retired, B31-3 (6-G) certified welder.

beastybaconman

Newbie

kennythewelder

Officially Retired, B31-3 (6-G) certified welder.

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