Well, it being a used vehicle, the transmission went out at 50k. I had seen the dealer's records on this vehicle (since I worked there as a service advisor) and knew all maintenance was up to date, but knew the previous owner did not believe in automatic transmission service. When I bought it, I also bought the General Motors Protection Plan, which replaced the transmission for free when it went bad at 50k. A few months later the ac compressor started to leak a little, and the GMPP replaced it for free. My wife drives the 99 Yukon, and she loves it. We replaced the Uniroyal tires at about 40-41k with Bridgestone Dueler HLs and replaced the shocks with Monroe SUV type shocks. At 98k miles we replaced the Dueler HLs with a set of Dueler ATs. It rode great with the HLs, but is now a little "trucky" with the ATs, which was expected. It got its first tune up of plugs and wires, a new serpentine belt, a new fuel filter, and a water pump that had been leaking about a gallon a month for a while was replaced too. I had replaced the front pads and rear shoes at the first tire change with Wagner parts and they appeared to have no wear on them when we put the new tires on it. We love the 99 Yukon, and if they are properly maintained with quality replacement parts, there is no reason why each one wouldn't go 500k. Maintenance is important for all motor vehicles, and the 99 Yukon is the best SUV (short of a Hummer) on the market. And the old plugs with 98k miles were worn but the coloration was ideal for a gas engine burning unleaded gas.