Low-low gear ratios have been part of vocational truck equipment for many years, and now customers of Volvo Trucks’ VHD can get them with the builder’s own automated manual transmission. I-Shift with Crawler Gears is the name, and greater performance and productivity comprise the product’s claim.
One or two extra ratios added to the builder’s 12-speed I-Shift HD allows easy starting under heavy loads and on steep grades, said Wade Long, director of product marketing, during a recent demonstration at the North American headquarters of Volvo Construction Equipment in Shippensburg, Pa.
The low-low ratios also allow very slow movement for special jobs like concrete and asphalt paving for mixer and dump trucks. With the C-1 gear, a Volvo VHD with the 14-speed version of I-Shift crawled at 0.6 mph, compared to about 2 mph for a 12-speed gearbox in normal 1st gear, he said.
This is especially useful for curb pouring. A local contractor brought in a forming machine whose hopper was fed by a VHD-mounted mixer as the machine and vehicle crept along. Meanwhile, press reporters drove VHD dump trucks on an off-road course that included short but steep grades, where upgrade starts were easy when using C-1 or C-2.
A driver engages the crawler gears by thumbing a switch on the T-handle of an I-Shift’s selector. With a 13-speed in the transmission’s 1st gear, one click puts it into Crawler. With a 14-speed, the first click gets C-2 and another gets C-1, the lowest (highest numerical) ratio.
The ratio of the lowest gear in a regular 12-speed I-Shift with direct-drive top gear is 15:1. In a 13-speed with one crawler gear, the ratio is 19:1 in a direct-drive transmission or 17:1 in an overdrive model. In direct-drive or overdrive gearboxes with two crawler gears, the lowest ratio is 32:1. The ratio of the lowest reverse gear is 37:1 in a direct-drive I-Shift.
Extreme startability also allows use in tractors pulling extra-heavy combination vehicles, Long said. The transmission will be approved for gross combination weights of up to 220,000 pounds, with prior application approval by Volvo engineers.
With overdrive top gears, a Volvo truck “can go down the highway at 1,330 rpm at 70 mph” depending on axle ratio and tire and wheel size, said Magnus Koeck, vice president, marketing and brand management. This saves fuel, speeds trip times and boosts productivity.
The I-Shift with Crawler Gears goes into production in October and can be ordered now. As with standard I-Shifts, they can only be had with Volvo D-11 or D-13 diesels.
Heavy-duty versions of the I-Shift, whether in 14-, 13- or 12-speed configurations, feature hardened gears and other hardware. The transmission received additional updates to improve shift performance and durability, including improved split synchronizer components, an updated engaging sleeve and main box parts made from reinforced material.
Although I-Shift penetration in highway applications reached 83% in May, only about 25% of construction-truck customers chose automated transmissions, Koeck said. The crawler-gear options are expected to increase that percentage.