Bought a bone stock 06 LBZ with around 390k. It drove around ok but had no power if you accelerated hard. Everyone was saying it needed injectors but it was the injection pump. EGR System was in place but I removed it at the same time as CP3. Original turbo, injectors, transmission etc. So there is some evidence of the completely stock engine and transmission making it to nearly 400k, although the CP3 probably needed replaced before that.
Adding some more detail to this for those who may be interested. PO had let me know the truck was on a rigorous fleet maintenance schedule and was adamant about using DELO motor oil every 3-5k and and Transynd transmission fluid every 50k. Also new Napa Gold fuel filter every other oil change. He had replaced front end parts 2 or 3 times including wheel bearings. Rear wheel bearings are apparently still original, and I recently put it on a jack to check to play or resistance but they seemed fine. Water pump and alternator were replaced at least once. Everything else original.
Once I started driving it, again the CP3 needed replaced right away. No lift pump. I worked out of it daily for a while and had some transmission issues come up when it was cold (Range Shift Inhibited). Took it on a long trip and right as I was getting home it started puking transmission fluid from a tranny cooler line. Did the hydraulic line upgrade + fluid/filter and strangely, the transmission issues went away, no matter how cold it is. I am guessing there was a blockage in the old lines, or perhaps the extra flow from the upgrade is just band-aiding the issue for now.
Put new wheels and tires on it and was recommended to replacing steering box at the same time. It did have a lot of play. New box tightened up steering a lot.
Took it on a 2000mi trip this summer and the original hydroboost started leaking really bad. Had to do a reman unit on the road and it is holding up for now. Just a few weeks ago took another 2400mi trip and had some weird brake trouble along the way. Did a hard stop and felt pulsing in the pedal. Limped to the closest parking lot, could hear a lot of noise from the right rear wheel. Backed up and you could hear the interference kind of fall out and clear itself up. Kept driving and around 75mi later, it happened again but completely locked the wheel. Had to have it towed and it ended up being that the parking brake assembly had rusted through and grenaded the rotating assembly. Rotors, calipers, spindle, etc. Again, had to have it repaired in the middle of a trip. They recommended doing the passenger side as well because it was ready to do the same thing. Found a great shop and although it was expensive, the brakes work better than ever and should last another 400k (except consumables)
Front end suspension is showing some wear again. I am thinking about going to SAS with the WFO Concepts kit. I know it will be more robust, but I am hesitant if I will take a hit with ride quality.