The Allison Transmission 4700RDS is equipped with a unique feature known as the Input Function Pump Mode, specifically the 4th Lockup mode. This function is designed to enhance the performance and efficiency of the transmission when operating auxiliary equipment such as pumps or fans driven by a split-shaft power take-off (PTO). In this article, we will delve into the details of this function and provide guidelines on how to select and engage it.
To begin with, it’s important to note that there are two variations of the Input Function Pump Mode (4th Lockup) available on the Allison Transmission 4700RDS. The first variation is Operator and Pump Activated, while the second variation is Operator Only Activation. Let’s take a closer look at each of these variations.
Operator and Pump Activated:
In this mode, the TCM (Transmission Control Module) commands a shift from Road Mode to Pump Mode based on the position of the Pump Mode switch and the positive engagement of the split-shaft PTO in the pump position. This function is enabled when wire #123 is switched to send power to the TCM, and a switch is closed to complete the circuit between input wire #122 and wire #103 (Signal Return). The selection of the Auxiliary (Pump) Mode by the operator is typically interlocked with the Parking Brake to ensure that the brake has been actuated before the operation of the auxiliary equipment is requested. A separate switch on wire #122 verifies the mechanical engagement of the split-shaft PTO. The function is only enabled when specific conditions are met, including the activation of the Parking Brake, selection of Pump Mode, full engagement of the auxiliary equipment, and Drive (D) being selected on the Shift Selector.
Operator Only Activation:
Similar to the previous variation, this mode is enabled when wire #123 is switched to send power to the TCM, and a switch is closed to complete the circuit between input wire #122 and wire #103 (Signal Return). The selection of the Auxiliary (Pump) Mode by the operator and the engagement of the Parking Brake are interlocked to ensure that the brake has been engaged before Pump Mode can be requested. A separate switch is used to detect the physical completion of the split-shaft PTO shift. The required operating conditions for enabling this mode are the activation of the Parking Brake, selection of Pump Mode, and Drive (D) being selected on the Shift Selector.
In both variations, when either of the input signals is disabled, the transmission resumes normal automatic shifting.
The table below lists the wiring schematics for input Pump Mode (4th Lockup):
To engage the Input Function Pump Mode (4th Lockup), follow these steps:
1. Select Neutral (N) using the Shift Selector to shift the transmission to Neutral.
2. Apply the Parking Brake.
3. Select Pump with the Dash Switch (PTO Switch ON), which turns on the “Pump Mode Requested” light. This action also activates wire #123, requesting “Pump” Mode from the TCM. When the split-shaft shifts, wire #122 is activated, and the “Pump Engaged/PTO” light turns on.
4. Select Drive (D) on the Shift Selector.
Once engaged, the following indicators will be displayed:
– Gear Commanded/Selected: 4th
– Shift Selector Range/Selected: 5
– Input #123 – Lock Up Pump Mode (FTPM): ON
– Input #122 – Pump Pack Enable: ON
– Output #145 – Range Indicator: ON
To disengage the Input Function Pump Mode (4th Lockup), follow these steps:
1. Select Neutral (N) using the Shift Selector. The transmission will shift to Neutral if the output shaft speed is less than 1000 RPM.
2. Select Road Mode to disengage the PTO (PTO Switch OFF). If the output shaft rotation is continuous, press the “Momentary Trans. Brake” switch before selecting Road Mode. This action will cause the transmission output shaft to stop if the transmission is in Neutral and the output shaft speed is less than 175 RPM.
Once disengaged, the following indicators will be displayed:
– Gear Commanded/Selected: Neutral
– Shift Selector Range/Selected: N
– Input #123 – Lock Up Pump Mode (FTPM): OFF
– Input #122 – Pump Pack Enable: OFF
– Output #145 – Range Indicator: OFF
The Input Function Pump Mode (4th Lockup) is particularly useful in commercial vehicles equipped with auxiliary equipment driven by a split-shaft PTO. By activating this mode, the split-shaft PTO engages, and the transmission shifts to 4th range lockup to power the auxiliary equipment efficiently.
In conclusion, the Input Function Pump Mode (4th Lockup) on the Allison Transmission 4700RDS provides enhanced functionality and performance when operating auxiliary equipment. By understanding the variations and guidelines for selecting and engaging this mode, operators can optimize the transmission’s capabilities and improve overall efficiency.
