i don't no a lot about dozers been working one for awhile an bought this one it has 7400 hrs on it . But has had good matinance done on it how many hrs are they good for before things need rebuilt
The machine should tell you when it's time. Undercarriage is kind of a loaded question. Depends on what conditions it's been ran in and how fast/hard the operators have pushed it. Oil samples would give you some idea of the drive train. Have you serviced it yet? Cat has magnetic pickup screens. They will tell you a lot as well. If it starts easy, pushes good, shifts smooth, overall seems to work good it should last you quite a few hours.