I have a 2007 cummins 3500 single wheel that is making a grinding sound when its at low rpm in low 2nd and sometimes 3rd gear and also reverse. it also sometimes jerks the truck when i mash the clutch in these gears. anybody have an idea about this? should i worry about it?

 

It sounds like the clutch is not completely disengaging the tranny from the engine. It could be your clutch's Master or Slave cylinders worn out. In my '03, they are sold together as a connected set and require no guessing as to which to replace and there is no bleeding required. Hopefully, same for your truck.

When you are at a complete stop on level ground, with the engine off, put it in 2nd gear. Start the truck and keep the clutch to the floor. Release the brakes and see if the truck is trying to creep forward. If so, clutch is not completely disengaging.

IMHO