2021 Mack Anthem - mDrive Transmission - Won't Shift into Gear

Question

Truck was working fine yesterday. This morning, I fire it up, wait for air to build, and when I put the mDrive selector into Drive or Reverse, the dash just keeps blinking 'N'. No grinding sounds, no clunking, it just refuses to engage.

I've tried the 'battery disconnect' reset for 20 minutes, which usually fixes glitches on these newer Macks, but no luck this time. The air pressure is a full 125 psi. Is there a brake light switch requirement I'm missing?

BoostedBryan · Accepted Answer

✅ Confirmed fix: The issue was the Gear Lever Console (the shifter stalk itself). These units have a known failure point where the internal ribbon cable cracks. Tested by swapping in a known-good shifter from another truck in our fleet, and it shifted immediately. Replaced the shifter assembly and calibrated through Tech Tool.

OTR_Carlos · Answer

Check the air supply line to the transmission clutch actuator. If the actuator doesn't see at least 100psi, it won't even attempt to move the shift forks. Listen for air leaks around the transmission while someone shifts the selector.

2021 Mack Anthem - mDrive Transmission - Won't Shift into Gear

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