a little knoking and leaking oil

[Waterloo]

That noise could be your air compressor, they all knock at start up, louder when in winter cold. If it is your air compressor knocking, it may be time for a new head kit. They are roughly $500 from Cummins, and you can do yourself. These compressors rarely fail, and are not cheap to replace. I went with the new compressor head kit, solved my knocking issues. That is, if it is your compressor! But that is where I would start.

The leak sounds like the gasket on the lower cover is bad, or it could be your front seal. If it is the front main crank seal, you do not have to disassemble the entire front end. Just remove the damper and front cover. The cover gasket is easy to replace, the front main seal you need a special tool from Cummins to install.

Oh, inspect that lower cover for damage. Sometimes road debris can hit it just right and break the gasket seal. The gasket itself is just an odd shaped round O-Ring. If you see a dent or deformation on the cover, that is more than likely the cause of your leak. The gasket itself is around $40, the cover is not cheap, but if damaged, may be fixable. If that is the issue.