Greetings folks! I'm a newbie here (but not new to forums) and I'm hoping one of you might be able to help with an issue I'm having with my '99 GMC 3500. I picked the truck up down in Florida around this time last year, after buying it on eBay. It's a utility body (with strobes and light bar) 6.5L turbo diesel, and had only 70k on the clock when I stole... err BOUGHT it for $5,500. Good rubber, dual rear wheels, 15,000 GVWR, excellent condition in and out, heck, the seats weren't even very dirty and they'd just repainted the utility body inside and out, and I'm real happy with it. I figure it's just barely broken in at this point. When I flew down to pick it up the fuel gauge was reading just above 1/4 tank, and the guy I bought it from said he just put $30 into it (with diesel then running about $5 per gallon). I took it and filled it up, both tanks, it took 35 gallons, and noticed right away that the fuel gauge was reading wayyy above full. Like a full half inch beyond the full mark. According to the book it's supposed to have a 21 gallon front tank and 18 gallon rear (or maybe the other way around - I forget) and that jibes with the amount of fuel it took to fill it from the 1/4 mark that first day. The problem is, the gauge is reading so high that it's not dependable. I can get about 125 miles before it comes down to the "F" mark, and if I fill it up at the 3/4 mark it takes around twenty gallons. I've never actually run it "dry", and I start getting nervous when it gets below 1/2 because I figure the way the gauge is reading "off" then 1/2 actually equals about 1/4. I'd like to correct this problem as simply and easily as possible. Anyone know if there's a calibration screw on the gauge? If I pop out the cluster can I get in there to adjust that needle? Or does this all have to be done through the computer? If it needs to be done through the computer it'll have to wait. The speedo reads a couple miles per hour low (65 is actually about 62) and I'm planning on swapping out the 4:10 gears for a 3:70 set for better highway mileage. Once I do that I need to get it to the dealer to recalibrate the computer for the new gears, so I can have the fuel gague calibrated at the same time, if it's a "computer only" type calibration.