Sorry if I could have searched the forum for this but I dont really know alot about this, this is just to help out my dad. His truck his leaking at the very front of the tranny, I got up in under it and looked and it looks like its coming from the gasket at the very front but I think its coolant. sorry the pics are really close up but I didnt have alot of room to work. the first pic is the leak itself and then the other 2 are pics of it slightly back towards the back end of the truck. just looking for some info on what it might be. thanks Zach. btw its a 2006 3500 crew cab 24 valve diesel with the 6 spd manual transmission.

 

Well, that's definitely not coolant.

Tough to tell from your pics, they're not real clear, but....

If that's at the front of the tranny, then more than likey is the rear main seal that's leaking.

 

As Coaltrain said its probably the rear main seal. How is the Clutch feel strong? When it gets wet it will slip.