Faced with taking its largest crawler loader to Tier 3 emissions compliance, John Deere decided to take a good look at the 755C Series II model in totality.
The result is the first Deere D-Series crawler loader, incorporating an updated operator's station, new computerized functions, and a new power train driven by the charge-air-cooled, six-cylinder John Deere 6068H turbo diesel generating 181 net horsepower and meeting Tier 3 certification.
"That's emissions-related, however, it gave us an opportunity to make the kind of changes that enhance performance at the same time," says Dan Drescher, product marketing manager with John Deere Construction & Forestry. "The C-II was a good tractor, but it needed to get modernized."
The crawler loader is a machine type not exactly renowned for smoothness, but the new 755D responds with a computerized proportional power boost that makes turns "smoother than any mechanical system ever could," says Drescher.
Moving through muddy conditions, with the standard 3.14-cubic-yard bucket fully loaded, would not be an unusual scenario for this machine. "Without the power boost, it's going to lug down and turn slower and not be very responsive," says Drescher. "With the power boost, it doesn't do that anymore."
Enhancing the output of a crawler loader is not simply a matter of increasing horsepower, he says.
"One function can't overpower the other; they need to be timed. Your ground speed should match what your boom raise and lower is, for the right conditions, so the hydraulics need to match up with transmission. It looks like it's a pretty basic machine, but there are a lot of challenges there to make it perform properly," says Drescher.
"It is a balancing act. A good example is, 'How long do your tracks need to be?' We actually shortened them up a bit on this one so that you have excellent balance," he says, "but it's easier to turn, so you are a little more maneuverable."
With 101 inches of track now on the ground, the 755's center of gravity was redefined on the D-Series model, resulting in a more balanced machine when fully loaded, says Drescher. A standard 2,090-pound counterweight helps boost the 21-metric-ton 755D's tipping load to 31,597 pounds. Breakout force of 36,869 pounds represents an increase of 18 percent over the previous model.
Up top, the addition of four inches to the door width makes for easier cab entry and exit for the operator. Once inside, visibility to the bucket is clearer, and the redesigned front-mounted monitor features illuminated gauges, a high-visibility screen, and audible/visual warning lights.
It is expected that D-Series upgrades will follow for the other members of the John Deere crawler-loader family —the 130-horsepower 655C Series II and 99-horsepower 605 C models.