I noticed a good amount of fluid on the bottom of my transmission and oil pan the other day. No drips on the ground though. Cleaned the area with brake cleaner to get a better idea of where it was coming from.

Within one minute i could see clear-ish fluid seeping from between the gear box and engine. Too clean for engine oil. Looks to be either manual transmission fluid or hydraulic fluid.

Any common/known issues in this area? Clutch feels fine and fluid reservoir was full.

My brake master cylinder has lost a little fluid over the past two weeks with no visible signs of where it's going.

2005 R53 98,000 miles - Manual transmission

 

In that area there are only two fluids (Oil and kinda close to hydraulic)... and unless there's a catastrophic coolant leak... it ain't that.

99% of the time in that area it's engine oil coming from the rear main seal.

Transmission fluid is red (correct me if I'm wrong)
Brake Fluid is amber (most of the time)
Coolant (should be) Blue

Since you've mentioned it's too clear for engine oil, then I'd look at the brake fluid... but that system terminates/cycles outside of the bellhousing... so how would it get inside? Same with the gear oil... not something that leaks out at that point...

Could it have been the brake cleaner you saw?
Can you post some photos?

 

Pull the boot back on the slave and see if the boot has brake fluid in it, if it does, then your slave is failed and needs replaced.

The mess you seen coming out of the mating surfaces soon after cleanup was almost definitely brake clean and runny mess that you can't get out of the bell housing without disassembly.

If it's an oil leak it could be either the crank sensor, valve cover gasket, or oil leaking from the green gasket between the supercharger and the plastic intake pipe (perks of a recirculated PCV system). All of these are common leaks, and far more common than a rear main that leaks enough to cause that large of an oil mess.

My guess is, since it's on the pan and bell housing that it's either the crank sensor leaking or blown by oil leaking from the SC gasket. Either of these are easiest fixed in a mild service mode, the crank sensor can be cleaned up really well and use black RTV to keep it from leaking ever again, the green gasket is just the nature of the system, it'll always leak.

 

I agree, check the slave cylinder. It's fluid would be amber in color.