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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).

  • Plan to pay for the inspection. End-play checks are typically billed as diagnostic time unless a dealer states otherwise.

  • 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 I would do (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 and expect to pay diagnostic time for an end-play measurement; bring this bulletin number (25-NA-307) to the service writer.

  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 full SI for P06DD (OCV, wiring, sensor plausibility, pump checks).


Source

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


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