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Replacing the Allison 9800 series with the TD 7600 series

    As the Oil & Gas market continues to pick up, Well Servicing Fleets are struggling to keep their fleets in operation. Palmer Johnson's Oil and Gas team has worked to position ourselves to help this market reduce downtime.

    1. Invested in approximately $2m in service parts inventory for the Twin Disc 8500 transmission packages.

    2. Increased our Twin Disc 8500 Reman swing packages from 2 to 9 packages, ready as needed.

    3. Invested in new Twin Disc 7600's transmissions stocked in Texas to be supplied as customers look to replace/retrofit their Frac fleets away from the Allison 9800 series transmission.

    This article was put together to help customers understand the advantages to the Twin Disc 7600 model which was designed specifically to meet this rugged market's demand and is a replacement option for the Allison 9800 transmission. We believe greatly that long-term there is a significant savings to be had by moving to an all Twin Disc fleet. Palmer Johnson is here to support the Aftermarket with best-in-class service both in the field, with parts and with product support around the clock.

    About the TD7600 series:

    Twin Disc 7600 transmissions were specifically designed to meet the heavy duty demands of driving triplex and quintuplex piston pumps for high pressure oil and gas well stimulation while matching the life of the diesel engines that power the rigs. These new transmission models are coaxial, nine speed, power shift transmissions with a maximum gross input power rating up to 1939 kW (2600 hp) @ 1900 rpm. They are designed for close coupled installation to the engines’ dry flywheel housing via a flexible coupling. The TA90-7600 & TA90-7601 transmissions are controlled by the advanced Twin Disc TDEC-500 control system and don’t require a torque converter for power shifting, instead use a master clutch. The TDEC-500 is the latest state-of-the-art full authority microprocessor based electronic control system for Twin Disc powershift transmission systems used in heavy duty, off-highway applications.

    Twin Disc 7600


    The competition of the TA90-7600 and TA90-7601 at their input horsepower range up to 2600 bhp @ 1900 rpm are the following transmissions: Allison S9820 net input rating 2250 bhp @ 1900 rpm Allison S9825 max. input rating 2600 bhp @ 1900 rpm Caterpillar CX48-P2300 max. input rating 2300 bhp @ 1900 rpm It was indicated at recent trade shows that the CX48 transmission will be capable of input ratings up to 2600 bhp @ 1900 rpm but no details were published to date. Please find a baseline comparison between the above competitive transmission and the twin disc models TA90-7500, TA90-7600 and TA90-7601 attached.


    Differences between TA90-7600 & TA90-7601 The TA90-7600 is a further development of the TA90-7500, adding a single speed planetary gearbox to the output which increases the 1st range ratio from 2.95:1 to 4.45:1 with an equal ratio step to 9th range. Due to interference of the transmission charge oil pump with the planetary gearbox housing, it was necessary to relocate it to one of the PTO locations. The TA90-7601 has the same main characteristics as the TA90-7600 but the rear main housing design was changed to move the transmission charge oil pump back to its original location. This will make the second transmission PTO available for customer use again. The main housing was also modified to be narrower below the mounting pad locations in order to allow installation between the narrow frame rails of standard heavy duty trucks in body load installations.

    The TA90-7601 will replace the TA90-7600 as soon as the inventory for the initial design rear main housing has been consumed.


    • Designed to match the engine life on pressure pumping rigs for oil and gas well stimulation. The robust, simplicity of the counter shaft design provides for an expected L10 life of 10,000 hours.
    • Designed specifically for the pressure pumping market, the transmission does not require throttle dipping for any of the range to range shifts. It is designed to be power shifted under all loaded or unloaded situations.
    • Lightweight yet durable aluminum housings to reduce overall vehicle weight.
    • Does not require a torque converter, further contributing to overall weight savings.
    • Compact in size and able to fit between the frame rails of mobile equipment.
    • Overall length of 1851 mm (72.9 in), shorter than Caterpillar CX48.
    • Small and evenly spaced gear ratio steps ensure that well pressure does not drop during gear shifts.
    • Simple plumbing to ease installation in the cramped quarters of a pressure pumping rig.
    • Two live PTO’s rated 149 kW.
    • Can in most cases use the same oil as the engine which simplifies the logistics for onsite fluids and the servicing requirements.
    • Includes a highly flexible coupling to reduce the damaging effects of the torsional excitations by the engine and piston pump.
    • Internal brake capability to hold the output shaft when not pumping.
    • The oil fill port is accessible from the ground. The competition’s oil fill ports are located on top of the transmission requiring the use of ladders, increasing the risk of fall injuries.
    • The oil fill port and sight glass are located in the same location, making oil fills a one-man operation.
    • Remote mount filters with electronic bypass indicators make servicing easy.
    • Existing TA90-7500 transmissions can be converted to the TA90-7600 with minimal rework.

    TDEC-500 Features:

    • On board built-in diagnostics.
    • Interactive display.
    • Health and trend capability with fault isolation via user accessible fault and status codes for all operational modes.
    • SAE J1939 CAN Bus and RS232 communication.
    • Environmentally tested to the highest industry standards.
    • Nonvolatile memory with real time clock giving time/date stamp for diagnostics.
    • Optimized gear shift performance for precise control of the high-pressure piston pump.
    • Flexibility to tailor features and operation for optimum performance.
    • Optimized line test mode specifically developed for the power shift transmissions of the TA90-7500 & TA90-7600 family.

    Application Requirements:

    As with all Twin Disc powershift transmissions, the TA90-7600 and TA90-7601 will require a full application review and factory approval before any commitment to a customer can be made. Please find the current application approval request form (SU144) for the TA90-7500 & TA90-7600 family of power shift transmissions attached.

    Installation Review and Shift Development:

    Any first installation of a new application requires an installation review by a Twin Disc field service engineer. After successful installation review and elimination of all found issues, a shift development is required and will be performed by personnel of the Twin Disc engineering department.

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