Oil Leak From Manual Transmission Housing

[k2em1]

A few months back I decided changing the flywheel and clutch disc on my 2008 manual e92 m3. This processed took 2 months as I was doing it in my garage and only spending time for it on weekends. I did not start my car during this time.

Finally I wrapped up everything and gave it a try. After a short round-trip around the block I came to inspect everything underneath the car and noticed an oil leak. I traced it and it is coming out of the hole between the transmission case and engine.

I have not opened the transmission yet but I guess this should be the engine oil (yellow) as the color does not match the transmission fluid color I used (red). I cleaned it up once and waited for a while, it does not leak when the car is standing cold and turned off, it seems it starts leaking when I take it for a spin.

I am wondering what are the things that could have gone wrong and what is possibly damaged?
- Can I say for sure this engine related and perhaps crankshaft seal related based on the color of oil?
- I noticed if put a jack and tilt back of the car, there seems to be some oil accumulated in the transmission housing and leaking rate get higher. (this contradicts the previous point right?)
- Slave cylinder related?
- I changed the input shaft seal as well, any chance that might be leaking? but would not that be transmission fluid?

I will also try inspecting things with an endoscope this week see if I can figure out the where is it coming from. Any other suggestions?

In any case do you guys think this might be another DIY thing I can fix or I should visit my mechanic, I just did this DIY for the sake of something to during pandemic but turned out to be much harder than what I think


Thanks in advance