Transmission upshift complaints

Service & Repair Truck Parts & Service Staff August 4, 2012

There have been complaints of Eaton automated transmission not making an upshift until the throttle is released or the transmission is upshifted manually. When this occurs, the gear display will indicate a solid current gear and with no upshift or downshift arrows, as well as no flashing “F” or transmission service light. The engine may be unresponsive to throttle input. The transmission ECU may not log fault codes.

Eaton says these complaints are shifting related, but vehicle systems can contribute to the problem.

Any of the following OEM vehicle interface conditions will cause a transmission upshift complaint:

Engine issues (fault codes, engine over temp, fuel system, etc.) causing derated engine power

Incomplete exhaust aftertreatment “regen” cycle resulting in derated engine power

Engine software change overwriting automated transmission settings

Engine governed rpm parameters below the transmission shift point rpm

Engine software compatibility issues

Change in transmission and/or engine programmable parameters (governed rpm, road speed limits, etc.)

Engine accessories (cooling fan, A/C, PTO, etc.) not operating properly

Data link (J1939) availability/message priority issues or faults

Other modules setting data link faults or overloading link

Intermittent data link failures

Unintended ABS/traction/stability control events

Engine And Aftertreatment Issues

Automated transmissions rely on engine broadcasted torque, speed and throttle data to determine when to shift the transmission.

When engine conditions occur that cause low-torque output, the transmission shift calculations will change, Eaton says. Accessory loads that are not operating properly are not figured into net torque correctly, causing biased shift calculations.

If a regen cycle on a 2010 exhaust aftertreatment system is not properly completed, the system will notify the driver with warning indicators and derate the engine, resulting in degraded shift performance.

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