2020 Volvo VNL 760 D13 - Intermittent 'Transmission Service Required'

Question

Dealing with a frustrating issue on an I-Shift transmission. Randomly, usually when stop-and-go in traffic, the 'Transmission Service Required' light hits the dash and the truck gets very 'clunky' shifting between 2nd and 4th gear. If I shut it down for 10 minutes, it clears up and runs fine for another 200 miles.

I took it to a local shop and they couldn't find any active codes, only inactive ones for clutch position. The fluid level is fine and doesn't smell burnt. I'm worried the clutch actuator is failing, but at $2,000 for the part, I don't want to guess.

CumminsCowboy · Accepted Answer

✅ Confirmed fix: Replaced the Concentric Slave Cylinder (CSC) and the clutch release bearing. The seals on the internal cylinder were bypassing air when they got hot, causing the P081073 Clutch Position Control fault. Once the transmission warmed up, the air leakage prevented the actuator from maintaining the correct position, leading to the clunky shifts.

GearheadGus · Answer

Check the air supply leading to the transmission. The I-Shift relies on consistent clean air to actuate the clutch. If the air dryer cartridge is old and passing moisture or oil, it will gum up the solenoid valves inside the shift tower or the clutch actuator, causing that erratic behavior.

2020 Volvo VNL 760 D13 - Intermittent 'Transmission Service Required'

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