Main seal or pan leak

[geunther]

Looking for your best guess based upon the pic. Looking at it, looks like the pan gasket for sure, but hoping to avoid the rear main seal replace. Just looking for other sets of eyes.

[HO455]

I'm going out on a limb here and saying it's impossible to be sure. When the engine is turning 2000 RPM it is a whirlwind between the block and the transmission with oil being flung out everywhere. The only time I have been truly certain the crankshaft seal is bad is when the crank seal is so bad it constantly washes the dust and debris from the crankshaft.
Personally I would do the crankshaft seal if the engine has a fair amount of miles on it.

[RustyPile]

Liquids always run down hill and drip off at the lowest point.. Just a suggestion, but have you checked areas farther up the "hill", such as the oil pressure sending unit or intake manifold where it seal across the rear of the block???

[weim55]

Originally Posted by RustyPile

Liquids always run down hill and drip off at the lowest point.. Just a suggestion, but have you checked areas farther up the "hill", such as the oil pressure sending unit or intake manifold where it seal across the rear of the block???

What he said, it could be one or even multiple leak locations. Anymore I just pull the engine and do a complete reseal. You can have the engine out of the truck in an hour or two, and doing all of that out of the truck beats the heck out of doing the bottom side on your back with oil dripping in your face.......

Steve weim55 Colorado

[Bobbysgmc]

I would put in the one piece felpro pan gasket and do the rear main seal at the same time.Did both of mine with engine in truck.Have to undo motor mounts and raise engine.Also look up what position to turn crankshaft to for best clearance for connecting rods.Cant remember what it is, sorry.

[JMD]

Like what was previously stated, oil leaks can be misleading because of wind rushing around while you’re on the road. I had oil all over the flywheel and the starter, and when I got on the highway it ended up on the rear cab glass and the tailgate...
Turns out it was coming from the oil dipstick tube, but it was impossible to tell because everything under the truck was drenched in oil. I only found the leak after I bought a $20 oil dye kit from Autozone. Best $20 I ever spent.

[geunther]

Thank you all. The pan gasket is pretty crumbly, and seeping pretty much all the way around. Touched the exposed part of it with a screw drive and parts of it crumbled off. Of course, the exposed parts have been exposed to the air for some 49 years. The other potential culprits (oil gauge line, back of valve covers, etc) all look good. Tranny leaking as well so attacking that too.

I researched on here and put the timing mark down but pan still won't come out. It was quite a chore to get the single bolt through the mount towers out with no room to work, but finally got that done. Bobbysgmc, do you recall how high I need to lift up on the engine?

Original plan was to pull motor to seal everything up, it has never been out of the truck so was wanting to avoid that if possible. Will likely do rear main seal at same time.

Thanks again all.