02 chevyHD 4wdwhat does it mean if oil presure goes up while driving?

It is suppose to go up. As engine RPM increases, so does the amount of "preasure" or flow of oil . Each engine/manufacturer has "limits" on the amount of preasure that any given engine can tolerate. If oil preasure "exceeds" these limits, it can lead to faliures within your engine....ie: blown gaskets, seals etc. If you are using a "thicker" viscosisty oil, this will also increase your oil preasure, especially during "colder" weather. Check with a dealer, they should be able to tell you what your perimiters should be for your oil preasure....low/high readings.