Is it normal for my truck to blow oil on my diff? Its not a lot but I was just curious, if this is not normal what would be the prob? Could someone explain to me exactly what blow by is? By the way my truck just broke 9,000 miles today if that matters.
thanks

 

Im pretty sure thats normal.

 

Front diff I would presume??? If so kinda normal.Check ENGINE oil and make sure not overfilled.

 

I noticed a bit on mine during my second oil change. Wiped it off. Third change it wasn't there.

 

Blow by is when the pistons rings aren't sealing properly and the cmpression during the compression stroke escaped past the rings and sown into the crank case

 

what you are seeing is not blow-by. It is simply the crank case breather. It is from the valve cover it vents off excess pressure and a little oil vapor. Once away from the engine it gathers back into oil dropplets and deposits itself on the front diff and if you get enough like me it will catch on the rear one also. But still be mindful about the diffs so that they aren't actually leaking. But just enjoy the cummins!!

 

It's an option you bought with the truck. It's the ULC (undercarrage lubrication system). DC put's it on all of it's CDT's.

A Cummins never leak, they are just marking their territory.