19 October, 2018
Understanding wheel loader transmission, axle and differential options
Wheel loaders today offer a number of options as it relates to powertrain components.
While size, horsepower and bucket capacities drive the initial loader identification/purchase phase, the next level of consideration - where decisions are made about transmission, axle and differential options - has a significant effect on long-term performance, productivity and total cost of ownership.
Even in the demo phase, operating a loader that is not the right match of powertrain to application and ground conditions can sway a purchase decision one way or the other, only to surprise the machine's owner when they get it into real world conditions. Worse yet: powertrain options not properly matched to the site can lead to excessive wear on tires and components, downtime, and lifetime maintenance costs much higher than they should be. It's also worth noting that operators should be properly trained in machine operation as it relates to the powertrain options selected.
All this to say: a clear and concise examination of a work site's conditions, loading and carrying cycles, and expected performance are required to make the optimal decision regarding a loader's powertrain.
CASE wheel loaders throughout the product line come standard with a 4-speed transmission. This 4-speed transmission is relatively common and perfectly suited for work in applications with short cycles - feed lots, stockpiling, aggregates plants, truck loading, etc.
Where the 5-speed transmission - available on CASE 621G, 721G, 821G and 921G models - excels is in applications where there is considerable travel or roading. The 5-speed transmission improves acceleration, travel speeds and climbing power, and can ultimately improve fuel efficiency. This may be particularly helpful for certain operations in municipalities, agriculture, quarries, etc.
On CASE G Series wheel loaders, the 5-speed transmission comes with CASE's POWERINCH feature, which provides improved accuracy and control in tight loading applications. It also comes with a lock-up torque converter that gives the operator more gear selections to keep the engine operating in its best power range, increasing fuel savings at roading speeds, and improving acceleration and hill climbing.
The takeaway: depending on the day-to-day tasks of each machine, you may find optimal applications for both transmission types in similar applications, sometimes even in the same jobsite/yard. The best choice will result from an understanding of the amount of travel required. For sites where multiple loaders are working, there may be an opportunity to establish work flows where both transmission types are deployed for optimal performance and productivity.
CASE wheel loaders come with either standard or heavy-duty axle configuration, and with that come varying differentials.
Open/Conventional: Power (torque) is delivered equally to the left and right tires for the axle, although the speed may change (like the inside tire spins more slowly than the outside tire). There is no input required here from the operator - the system just operates as it was intended.
Limited Slip: A greater percentage of tractive effort is provided to the tire with better traction to help power through changing conditions (like slippery terrain, or transitions from dry to wet environments). This also provides for consistent drive power in slippery conditions on side slopes.
Limited slip is ideal for snow removal applications or when operating on loose, uneven ground. It is generally not recommended for use on improved surfaces, where tire scuffing can occur due to steering, which gives the appearance of tire slip based on the system's design.
Locking Differentials: This style provides up to 100 percent of the available power, equally to the left and right wheels. Traditionally best used by experienced operators or where condition variances are expected. Ideal for applications involving constant operation on improved surfaces and short cycle loading applications. The locking differentials provide more power to the ground when digging into a pile, and the sintered bronze brake discs increase performance and life.
These can either be automatic or manually engaged. Auto is switch activated for the system to monitor and activate the differential based on internal operating conditions. Manual operation is based on a floor switch activation by the operator.
Locking differentials are designed for heavy duty, high capacity operations and are rated for use with heavy-duty axles - especially when set to automatic, as the operator can simply set it, forget it and operate. Manual engagement should only be done by experienced operators - less experienced operators have a tendency to engage the differential when the machine is already experiencing slip, which is detrimental to the system and can degrade components, leading to potential mechanical issues over time.
Axle and Differential Combinations
The standard axles are ideal for working in mud, unfinished or otherwise soft/soupy conditions. Those that come standard with limited slip differentials deliver power to the tire with better traction to help power through challenging underfoot conditions while also preventing the tire that does not have traction from scuffing or experiencing excessive wear.
Heavy-duty axles on CASE wheel loaders offer a hydraulically locking differential on the front axle and an open rear axle (although dual open differentials are optional on select models). These axles are more robust and designed to handle hard-working production environments. It is generally recommended to run heavy-duty axles for loaders operating mostly on improved surfaces (pavement, hard-packed gravel) - this is especially accurate in applications such as waste handling where solid tires are used.
The actuation of the diff lock provides high traction with both wheel outputs locked together. The open rear differential provides lower frictional losses in the axle, ultimately increasing fuel efficiency and reducing tire wear. This axle/differential combination is ideal for high hour, large-scale production environments with solid underfoot conditions.
Other applications where heavy duty axles are recommended include foam-filled tires, tire chains, applications where consistent pushing is performed (basement digging, waste, etc.), short cycle truck loading at low speeds (below 6 mph), high break use environments and the use of oversized attachments (such as log grapples).
As with any equipment choice - every application is different. Talk with your local dealer or manufacturer rep before you deploy your next fleet of wheel loaders to determine the best match of transmission, axle and differential for your application. For more information on the entire line of CASE wheel loaders, visit: www.casece.com/northamerica/en-us/products/wheel-loaders
Source: Case Construction