Oil Leak Near Bell Housing Help

[OchoCinco]

I noticed some oil droplets under my truck after letting it sit for a week. Looks like it is coming from within the bell housing (not 100% if that's what is called). I recently had the engine oil pan gasket replaced and it looks clean in that area. I changed the valve cover gaskets as well. My suspicion is after I had the transmission rebuilt the shop did not check out the rear main seal like they said they did and that may be the culprit. Any opinions?

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[WFO]

I'd say rear main seal if it's oil, or front transmission seal if it's red.
Check high on the rear of the engine first, though. Could be valve covers, distributor gasket, oil pressure fitting or intake gasket (China wall).

 

[Craig Nedrow]

looks like engine oil, not tranny fluid

 

[QBuff02]

I'd re-snug the oil pan bolts if the gasket was just replaced. Also, if the oil pan gasket was replaced and they didn't silicone the corners of the seals at the pan/main cap junction, oil is known to seep out of those locations. I'd pull the converter inspection cover and get an eye on everything in there. With the cover off you can look right up at the back of the crank and see the area of the seal to determine if its coming out of the rear main. I had a similar situation when I rebuilt my 454, kept thinking it was the rear main seal must've been damaged during assembly, but come to find out I put a quart too much oil in the pan and the crankshaft was picking the oil up and slinging it and causing it to seep out of the back right corner of the pan gasket. ventured to guess it was waterfalling off that area of the block internally. It would only drip after i'd been out winding the thing up. But I had also noticed that my oil pressure would wildly fluctuate 8-10lbs above 5,000rpm and it was because the oil was getting aerated by the crankshaft. The drip was just enough to be a nuisance, but after discussing the oil pressure fluctuation with my engine guy I took a quart of oil out and the drip dried up and the oil pressure fluctuation went completely away. That's what it was in my particular situation, but for you, i'd start with checking things over under the converter cover and snugging the pan bolts up.

 

[OchoCinco]

I'd re-snug the oil pan bolts if the gasket was just replaced. Also, if the oil pan gasket was replaced and they didn't silicone the corners of the seals at the pan/main cap junction, oil is known to seep out of those locations. I'd pull the converter inspection cover and get an eye on everything in there. With the cover off you can look right up at the back of the crank and see the area of the seal to determine if its coming out of the rear main. I had a similar situation when I rebuilt my 454, kept thinking it was the rear main seal must've been damaged during assembly, but come to find out I put a quart too much oil in the pan and the crankshaft was picking the oil up and slinging it and causing it to seep out of the back right corner of the pan gasket. ventured to guess it was waterfalling off that area of the block internally. It would only drip after i'd been out winding the thing up. But I had also noticed that my oil pressure would wildly fluctuate 8-10lbs above 5,000rpm and it was because the oil was getting aerated by the crankshaft. The drip was just enough to be a nuisance, but after discussing the oil pressure fluctuation with my engine guy I took a quart of oil out and the drip dried up and the oil pressure fluctuation went completely away. That's what it was in my particular situation, but for you, i'd start with checking things over under the converter cover and snugging the pan bolts up.

Thanks! I'll get under there today and check it out.

 

[dvdswan]

What we have here is a clean drivetrain and undercarriage. Had you left it all original you would not have noticed the issue.

 

[Brad G]

I had the same leak the I couldn’t find, everything was brand new! The bolts for the flywheel go all the way through the crank flange. So, they can “weep” a little oil. Put some thread sealant on the threads! My leak went away when I did this!

 

[PrairieDrifter]

I had the same leak the I couldn’t find, everything was brand new! The bolts for the flywheel go all the way through the crank flange. So, they can “weep” a little oil. Put some thread sealant on the threads! My leak went away when I did this!

Not sure what motor you have but I don't believe big blocks do, and I'm positive small blocks don't.

 

[idahovette]

Have never seen any flywheel bolts that go into any "oil" passages to "leak" oil on any Chevrolet engines???

 

[PrairieDrifter]

Have never seen any flywheel bolts that go into any "oil" passages to "leak" oil on any Chevrolet engines???

That's my thought as well, I know for sure some other manufacturers do. Just wasn't 100% on the big block, or if it was a crate engine maybe? I assumed they wouldn't change much stuff like that, hell at least we're not like Ford with their big block and small block bell housings lol.

 

[Raider L]

Yeah, take the converter cover off and snug the few bolts at the back of the pan. If you're using a cork gasket just be careful and don't tighten them down two much. Like, they're supposed to swell up and seal between the parts to stop leaks. But if you over tighten those screws in a cork gasket, and it swells it'll split the gasket. Better to wipe the back of the pan and leave the converter cover off, drive around the block a few times and park the truck, wait a while and look back up in there to see if oil is ozzing out from between the pan and the rear gasket.

Like @QBuff02 said, was there enough RTV on those corners? If not I don't know any way to get sealant in the corners of the pan with it in place other than taking the pan loose some and get some sealant in the corners and put the pan back and screw it down. And hope for the best.

 

[Bextreme04]

That's my thought as well, I know for sure some other manufacturers do. Just wasn't 100% on the big block, or if it was a crate engine maybe? I assumed they wouldn't change much stuff like that, hell at least we're not like Ford with their big block and small block bell housings lol.

No, none that I have ever seen. Not even the LS motors have holes that go through to an oil passage.

 

[Bextreme04]

I noticed some oil droplets under my truck after letting it sit for a week. Looks like it is coming from within the bell housing (not 100% if that's what is called). I recently had the engine oil pan gasket replaced and it looks clean in that area. I changed the valve cover gaskets as well. My suspicion is after I had the transmission rebuilt the shop did not check out the rear main seal like they said they did and that may be the culprit. Any opinions?

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I agree with everyone's replies above. Pull the inspection cover and see if the oil is INSIDE the cover. If its inside, you are almost guaranteed to have a rear main seal leak. Its entirely possible it wasn't leaking when the trans shop had it off and it just started leaking after sitting for a few days... that's kind of what these engines are notorious for