Was sitting in my driveway the other day and noticed my fuel gauge bouncing around (about a quarter tank fluctuation). My drive has a slight incline and as long as the truck is in N or P it's stays steady. As soon as I put it D or R it starts fluctuating again. I thought maybe the RPM drop when you put it in D or R had something to do with it if it was a wiring problem, but I can jack the RPMs up and down in P or N and it still stays steady. On level ground I don't have this problem. Another strange thing about this is whenever the fuel gauge bounces high and I put the truck in gear the gauge will stay at that level for about 5 minutes and then slowly begin to drop to the correct reading. Any ideas before I go digging in the tank?

 

Never seen that happen on any of my trucks but for some reason the last 1/4 of my tank goes quick. I wished it was consistent.

 

I've noticed that on mine as well. I work with a guy that's got a 99 silver and he says the same about his. Must be a design flaw with GM.

 

The fuel gauge is a problem on alot of NBS trucks. Mine goes all over the place when I fill the tank. Every NBS truck that I know of has the fuel gauge issue.