I just picked up a GMC Suburban K2500 6.5 Diesel with 42000 miles. It's your base truck with good hauling power, I believe it's an Ex County Truck from Florida. Here is my problem, the Voltage gauge hardly goes over 11 volts, but when you put it on a meter it's says 14volts. When I was driving home from Florida to NC, The gauge kept going lower and lower finally getting to the 9 Volt range. So I pulled into Brunswick Ga to get gas and it won't start. Got jumped by AAA, who from his jump box said it was charging. About two miles from there on I95 the truck starts to run poorly, the transmission is slipping, so I pulled over on a Truck weight station, open the hood and twist the positive cable on the passenger side battery, the truck while still running, springs to life. So I drive further and pull over for the night. It starts the next morning and I make it back to NC. I take it to a local GMC for a few other issues I saw on the drive home, the Service Engine Soon light would come and go, leaky A/C into the cabin. I get it back yesterday and it shifts like it's low on fluid, hits real hard. Today I purchased new screw in battery poles, replace three of the four, clean the connections tighten that loose cable and while driving it around town it drives Ok, like it did on my way home from FL. But the gauge is dipping down again just above the 9. So I decide to replace the alternator with a new one and a new belt. On my way home from Sears, The gauge diped lower, so I pull over into the local GMC dealer because the transmission is not shifting properly. Turn it off and try to start it, Dead again. The batteries look like they are new, the stamps show march of 09... Anybody else ever hear of such an issue? Sorry to go on, but I am frustrated.