Do I need a new rear main seal?

[chapelno]

Changed the oil today - went from 10W-30 dino, "whatever was on sale and I was in a hurry oil," to 10W-30 Mobil 1 high mileage full synthetic. As I'm replacing the oil I notice a puddle under my transmission. About half a quart leaked out - I think through the seams between the engine block/bell housing and bell housing/transmission case. This is my third oil change in this truck (198,000mi, I got it around 185,000mi) but first using full synthetic.

The below pictures are from driver's side and passenger's side of where the housing and transmission case meet. You can see the line of oil that follows the seam. The leak was gathering on the transmission pan protector and dropping to the ground. I assume this means the rear main seal is bad and oil is making its way past the crankshaft and into the transmission.

My questions:
1) Is there another cause to explain these symptoms? Anything else I should look for?

2) When I have the engine/transmission out and apart to replace the seal, what else should I replace/fix/check/clean? I'm on a budget so will focus on cleaning, but if there's a must do I'll tackle it. The galley plug and oil pan gasket are on the list - what else?

3) On both sides of the transmission, there are two bolt holes (circled in red in the last photo) without bolts. Should I be worried about this?

4) I guess I should Rodney flush the transmission to get out any oil contaminant? Any other concerns with the transmission?

Thanks for any tips.

 

[Wile E Coyote]

Im on my phone and your pics arent showing up...having said that, your trans is safe. The engine oil will not mix with the transmission oil from a RMS leak.
It's common on our vehicles for the oil pan to leak in that area. Yes, it looks quite like a RMS leak. Also, look for things like a valve cover, galley plug, or even oil cooler to leak down from above.

 

[chapelno]

Fixed the photos - apparently photostream's URL is a moving target.

I've had a consistent leak just behind the oil pan (kind of dripping off the bottom of the bell housing where the access cover is) for a while, but not enough to be too concerned about. Maybe a drop a day. The engine has a decent coating of gunk on it, but it didn't look like it was coming from the cooler or higher up on the engine.

Good to hear about the transmission fluid.

 

[chapelno]

Bumping this once before I order up the whole engine gasket kit. Do y'all think it's worth trying the oil pan gasket, or is that oil around the transmission seams a solid indicator the rear seal is kaput? Thanks for the help.

 

[Alleycats]

Maybe try a thicker oil like 5w 40 or 10w 40? I'm running rotella T6 5w 40 and my 3fe seems pretty happy. Also it starts just fine on cold mornings.

 

[rayg]

Common problem when changing to synthetic oil. See this GM forum: http://forums.gmhightechperformance.com/70/6662987/ltx/high-mileage-switch-to-synthetic-oil-leak/

 

[chapelno]

I'd read about the dino -> synthetic leak - looks like I'm a victim in possibly multiple areas. I'm going to go ahead and use this as an opportunity to pull the engine, scrub it clean, and replace all the seals. Wish me luck.