LZ0 3.0 Duramax: GM Flags Crankshaft End Play Behind Bellhousing Noise & P06DD (25-NA-307)

Published: October 1, 2025Bulletin: # 25-NA-307 (Released September 30, 2025)Applies to: 2025–2026 Chevrolet Silverado 1500, Suburban, Tahoe; GMC Sierra 1500, Yukon models with LZ0 (MQB, MQC). Region: North America.Symptoms: Bellhousing-area engine noise, MIL on, DTC P06DD (Engine Oil Pressure Control Valve Performance).

TL;DR (What owners need to know)

• GM bulletin 25-NA-307 links bellhousing-area noise plus P06DD to excessive crankshaft end play—often from thrust bearing failure.

• Dealers are instructed to measure crankshaft end play at the crank pulley bolt with a dial indicator. Spec: 0.084–0.316 mm (0.0033–0.0124 in).

• Diagnostics are typically covered under warranty however some instances may warrant a dealership to request diagnostic time.

• If out of spec, additional teardown/repair decisions follow standard service information.

  
  

What’s happening

Owners/techs are reporting:

• Mechanical noise from the bellhousing area (rattle/knock near the converter/flexplate)

• MIL illuminated with P06DD

GM’s bulletin points to excess crankshaft end play as the underlying condition. Excess axial movement can upset oil-pressure control behavior, which helps explain the P06DD set on the LZ0 platform.

Affected vehicles

• 2025–2026 Chevrolet Silverado 1500, Suburban, Tahoe

• 2025–2026 GMC Sierra 1500, Yukon models

• Engine: LZ0 3.0L Duramax

• Transmissions: MQB, MQC

• Region: North America

  
  

Dealer diagnostic procedure (summary)

Per 25-NA-307:

1. Remove the torque-converter access cover (bellhousing inspection port).

2. Gently move the torque converter fore/aft with a pry bar to load/unload the crankshaft.

   • Note: You will flex the flexplate; the converter will appear to move more than the crank.

3. Measure crankshaft end play using a dial indicator with the base on the block and the probe on the crank pulley bolt.

4. Compare to LZ0 spec: 0.084–0.316 mm (0.0033–0.0124 in).

   • Out of spec: Proceed with SI for thrust-bearing/crank evaluation and repair path.

   • In spec: Continue normal SI diagnostics for P06DD and bellhousing noise.

     
     

What Options Are Available? (owner checklist)

1. Record the symptom (short video/audio near bellhousing; note mileage/date).

2. Scan for codes and save the report (freeze-frame if available).

3. Schedule an inspection for an end-play measurement; bring this bulletin number (25-NA-307) to the service writer. (Edited- there have been reports of inspections covered at no cost)

4. Ask for the measured end-play value on the repair order and compare to spec (0.084–0.316 mm / 0.0033–0.0124 in).

5. Maintain correct oil level/viscosity and bring recent oil-change receipts.

6. If end play is out of spec, ask the advisor to document “excessive end play / thrust bearing concern per 25-NA-307” and request the shop’s next steps and timeline.

   
   

FAQ

Is this just another generic P06DD situation?No—on LZ0 with bellhousing noise, 25-NA-307 specifically calls out crank end play / thrust bearing as the suspected mechanism. Other engines may set P06DD for different reasons.

Will I need an engine?The bulletin doesn’t prescribe one repair. The path depends on inspection findings (bearing/crank wear, debris, etc.) and standard service information.

Can I keep driving?If you have distinct bellhousing-area noise plus a MIL, it’s prudent to minimize driving and book an inspection. Mechanical concerns tied to end play can escalate.

Editorial tips for techs

• Rigid indicator setup is critical—probe on the crank pulley bolt with the base on the block.

• Because converter/flexplate visual motion can mislead, don’t reference converter movement for the measurement.

• If end play is in spec, follow SI for P06DD (OCV, wiring, sensor plausibility, pump checks).

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Source

• GM Service Bulletin 25-NA-307, “Information on Engine Noise from Bell Housing Area, MIL On – DTC P06DD Set,” Released Sept 30, 2025