2016 Mack Pinnacle - Transmission Shifting Hard/Hanging - mDrive Issues

Question

The mDrive in my 2016 Pinnacle has started shifting really aggressive lately. Especially when downshifting from 6th to 5th, it feels like someone hit the truck with a sledgehammer. Occasionally it stays in 'Neutral' for too long during a shift and then bangs into gear.

I've checked the air supply to the transmission and it's holding steady at 120psi. No air leaks heard from the shift tower or the solenoid bank.

ChevyChuck · Answer

Check your clutch brake. If the clutch isn't fully disengaging during the sync phase of the shift, the mDrive will struggle to line up the gear speeds, leading to those hard hits.

RoadDawgRicky · Answer

✅ Confirmed fix: The issue was the Gear Position Sensor on the top of the transmission. It was sending erratic signals to the TCM, making the computer think the shift hadn't completed yet, causing the 'hanging' and then slamming the clutch. Replaced the shift actuator assembly (which includes the sensors) and did a full teach-in with Tech Tool.

2016 Mack Pinnacle - Transmission Shifting Hard/Hanging - mDrive Issues

Suggest a repair