Rear Main Seal Leak?

2000 4x4 2.7L 5spd 219K miles

I just had basically the whole front end replaced. All BJs, CV axles, outer tie rods, and steering rack and pinion. Last night, I got underneath to take a look at the work. I noticed black steaks right in the center of the rack and saw some fluid buildup in the opening circled in red in the picture attached. This picture isn’t my actual rig. I had already wiped it clean before I decided to post here.

The fluid was super black, as black as satan’s heart. It honestly doesn’t smell like much, can’t differentiate between motor oil of trans oil. I just changed the motor oil about 2.5K miles ago and it’s still got some amber to it. The mechanic said he topped off the manual transmission fluid.

I’m pretty sure this is the rear main. I did replace the valve cover gasket back in Jan and the seams are bone dry now, so that’s not a worry.

Any ideas here? All input is greatly appreciated!

 

RMS good guess
But
I would power wash bell housing and surrounding area/brake clean
Then monitor

as the very bottom of bell housing is clean(u can see metal) could be the ATF from steering rack or lines
Getting moved there by air flow while truck in motion
ATF is a detergent by definition

 

Manual trans

 

ATF used in power steering system

Rear main seal would seep engine oil


Just need to confirm best u can by cleaning and then determining what fluid is seeping