well i just noticed that if a stop hard my oil pressure light comes on and my pressure goes to 0, i get off the break and then it goes back to 40. it only does this some times, and the oil level is fine, i cant think of anything

 

I have read of this before and some commented that it was normal and nuttin to be concerened of..................the pressure is fine its all in the sender , basically as long as the motor is turning you have good oil pressure

 

ok take a deep breath and grab a cold one , i would start with the sending unit located just under the injection pump if that checks out check for possible bad wire possibly broken inside the insulation (pain in the but and time comsuming) can do it with either a volt meter or with truck running and a second person watching gauge to fall while you wiggle the wires, also so far sounds like just a bad sending unit , dont stress

 

On the oil filter head there is a second port - you can remove the plug and screw in a temporary 1/8" NPT guage to verify that your oil pump is working fine.

That being said, 99% of the time, the sensor has simply went bad. Get a new one from Cummins: p/n: 3923200. The ones from the Auto Parts Store dont last very long - go with the Cummins part.