depends on what engine, chevy v8 have been around for a long long time, the 5.3 and the 5.7 are both strong running engines, and taken care of will last 300,000 miles, the tranny sometime was not as good, but would still get a couple hundred thousand miles, but once rebuilt with a quality rebuild kit, it was ready to go the distance no matter what you did. These are pretty durable vehicles, and take it to a mechanic and get a good diagnostic done by your trusted mechanic. I looked up the avalanche on www.nada.com a clean trade in books around 9,200 and change, with just over 12,500 as high book, the 3/4 ton is built from real truck parts, so is a heavier duty truck, the 4x4 will cost you a fortune in gas, it has auto lock hubs, so they front drive line is always turning, which turns this into a gas sucking pig, the vortec motor, and the newer multipoint ? or multiport? fuel injection with the 5.3 will be better than the 5.7 but still, 12 to 14mpg in the highway. Its a big heavy truck, good four by four, great two vehicle with good bottom end torque, but you pay for it.
