Way back in the old days, they used cables to control the blade. No hydraulics. Most people avoid these older dozers because of there age, difuculty in finding parts and extreme wear.
I looked at a 1969 D7 for $20,000 near Dallas before buying my dozer. It had more leaks and issues than I wanted to mess with, especially on a machine that large and old. Cat had the parts in stock to fix it, and the prices weren't bad, but I didn't want a project to work on, I wanted one to do work with.
In my opinion, Dozers under 100 hp are fine for clearing brush and grading soils. They aren't very effective at tree removal or digging massive amounts of dirt. The John Deer 450 that I ran couldn't break the surface of the red clay on my place. The guy who bought the land I sold brought in a guy with a small D5 who had to use rippers to break the surface first.
Dozers over 100hp to the mid hundreds are big enough to do most jobs you'd need. The can take out fair sized trees without to much effort and move enough dirt to make it worthwhile.
The bigger ones like a D7 and up are way overkill and unless you got a really good deal on one, I'd shy away from them. If you can afford to buy something that large, there's gotta be a reason it's being sold for so little. Big machinery costs big bucks!!!!
Just my thoughts,
Eddie
