I agree about the manuals. worth the money.
My dad and I bought our first dozer used. A d4 cat, 40n series. We bought in 1973. think it was an early 60s year model. We spent $179 on a manual. That was an arm and leg back then. If memory serves, shop time was $20 per hour and that is what we charged for dozing work. It seemed like highway robbery. Was best money we ever spent. we rebuilt the final drive (twice), did a head job, adjusted the oil clutch numerous time, and did all sorts of other work on it, that would have been impossible for use,without the manual. We wore the dozer out 3 times over, and I finally ran it to destruction and sold for scrap iron in 2012. It would have been scrap metal 10 years after we got it, had it not been for the shop manual we bought!