I've been thinking of getting a bulldozer, and I'm wondering what the typical service life (time between rebuilds) is for a hydrostatic drivetrain in a dozer, and how it compares with the life of a power shift. What are your experiences?
That's a good question. I've seen juice boxes on dozers at around 6,000 hours but not seen failures at that time frame on anything other than bad maintenance. I'm told that if you trash a pump the cost of the repairs will easily run over the value of the machine. I've seen lots of 10,000 hour plus power shifts and they have been around long enough that you have a handle on how long they last. How big of a machine are you looking for?
Like all hydraulic systems a major failure on a hydrostatic can be really costly because of the amount of debris it generates and the effect on all the components downstream of the failure. If you had a hydrostatic I'm guessing you'd really want to get into oil analysis & Contamination Control in a big way to make sure your hydraulic system was clinically clean all the time. Powershift systems are a bit more forgiving (but not much) their benefit is not so many components in the system with eye-watering replacement prices.
I'm thinking about a D5 or D6 sized dozer. Do you think a hydrostatic dozer with 8-10k hours will last a couple thousand more hours without a rebuild? I guess oil samples would be particularly important in judging a higher hour hystat. I'm on a rather tight budget, and so I'll probably be looking at higher hour machines. I have experience with powershift wheel loaders (mainly cat), and on them, I've found that the transmission usually lasts 15k+ hours without any serious issues. Should the transmission life on a midsize power shift dozer (like a D5M or D5H) be comparable?
As long as they haven't been overheated and the maintenance is done when required, they will last just as long as a wheel loader. I haven't seen any of the hystats out 12,000 hours yet. That doesn't mean they haven't done it, only that I haven't looked at any yet. Good Luck!
If you get a high hour hydrostat just look at a rebuild/replace on the pump just to be safe, you don't want that to trash the whole thing. It could be more that 5k on replace or around 1-2k on rebuild if you do it yourself. Just check your specs on the pump if you rebuild. New anything brass, check the slippers on the piston and a new swash plate and bearings/seals of course. Done it many time with no problems.