It doesn't look like boot grease though. It isn't thick enough to be grease. That is really strange. The mount does look shot though, so that needs replacing. I would ride it out but be weary of a tranny fluid leak because that is what it looks like to me from the pics.

 

Is it wet around the axles where it connects to the transmission? If so, then you need new axle seals.

 

Wouldnt he be leaking tranny fluid if that happened though?

 

axle seals dont usually leak a noticable amount on the dipstick but will give the undercarrage that "wet" look. also look for a spray pattern on the underbody, usually the tranny fluid will "sling" off the rotating axle leaving a line of fluid along the firewall and the underside of the tranny

 

rear main seal... hnoes: