LZ0 Thrust Bearing Failure: Did This Engine Teardown Finally Reveal the Cause?

The mystery surrounding LZ0 thrust bearing failures may finally be getting some answers.

Over the past year, owners of 2025 and 2026 3.0L Duramax-powered trucks have reported excessive crankshaft end play, low oil pressure warnings, thrust bearing failures, and complete engine replacements. While GM has provided diagnostic procedures and replacement guidance, the actual root cause behind these failures has remained largely unknown.

This week, I tore down an LZ0 engine that failed at approximately 7,500 miles. What I found was unexpected.

Before we go any further, this is a sample size of one engine. I'm not claiming every failed LZ0 has the same root cause. However, what was discovered during this teardown deserves serious discussion.

Watch the complete teardown video: https://youtu.be/to-UC_LXz_8

Listen to the podcast discussion: https://youtu.be/DWGz_Vfe4TY

Watch how to check crankshaft end play: https://youtu.be/0ydF8yuJgoE

The Engine

This particular engine came from a June 2025-built truck and arrived at the dealership still running.

Unlike many catastrophic engine failures, this engine had not seized. The vehicle exhibited excessive crankshaft end play and a low oil pressure condition, ultimately resulting in engine replacement.

Because the engine was still operational, I expected to find most of the failed thrust bearing material somewhere inside the engine.

That is not what happened.

Initial Findings

After draining the oil and removing the oil pan, several important discoveries were made:

• One damaged thrust bearing was found in the oil pan.

• Additional thrust bearing fragments were recovered.

• Threaded metal debris was discovered.

• A significant amount of contamination was present despite the engine still running.

One interesting side observation involved the amount of oil left behind after a normal oil change.

After draining the oil and removing the pan, a surprisingly large amount of used oil remained trapped in the bottom of the original oil pan design. This further supports GM's decision to revise the oil pan design on later production engines and replacement engines.

At first glance, however, this looked like a fairly typical thrust bearing failure.

As the teardown continued, things became much more interesting.

The Discovery

Once the lower crankcase was removed and the thrust bearing area became visible, something immediately stood out.

Only one thrust bearing appeared to be present.

The opposite side was empty.

The crankshaft thrust system is designed to control forward and rearward crankshaft movement using thrust bearing surfaces on both sides of the crankshaft. However, after inspecting the engine from top to bottom, only enough bearing material was recovered to account for approximately one thrust bearing assembly.

The amount of debris simply did not match what would be expected if two thrust bearings had been installed and one failed catastrophically.

No additional thrust bearing material was found in:

• The oil pan

• Lower crankcase

• Timing area

• Oil pump area

• Remaining engine internals

The teardown revealed one damaged thrust bearing and evidence suggesting the opposite bearing may never have been installed.

Could This Explain the Failures?

If this engine was assembled with only one thrust bearing, several observations suddenly make sense.

The remaining thrust bearing would be forced to absorb all crankshaft thrust loads by itself. Over time, wear would accelerate until excessive crankshaft movement developed.

Once that happens, secondary damage becomes possible:

• Excessive crankshaft end play

• Low oil pressure conditions

• Contact with nearby engine components

• Metal contamination throughout the lubrication system

Those symptoms closely match what was observed in this engine.

Again, this does not prove that every LZ0 failure is caused by a missing thrust bearing.

What it does provide is a plausible explanation for this particular engine, which exhibited the same symptoms being reported elsewhere.

The Oil Squirter Discovery

Another interesting finding involved the threaded metal debris recovered from the oil pan.

Initially, the debris appeared to be portions of a bolt.

As the teardown progressed, it became clear that a piston cooling oil squirter had been damaged.

The remaining question is whether the damaged oil squirter was a result of the thrust bearing failure or whether it somehow contributed to the failure.

At this point, there simply is not enough evidence to say.

What we do know is that excessive crankshaft movement was present, and a damaged oil squirter was found in the same area.

For now, it remains another clue worth tracking as additional engines are inspected.

How to Check Crankshaft End Play on Your LZ0

If you're concerned about thrust bearing failure, one of the simplest inspections you can perform is a preliminary crankshaft end play check.

This is not a substitute for GM's official measurement procedure, but it can help identify engines that may require further evaluation.

Watch the step-by-step inspection video here: https://youtu.be/0ydF8yuJgoE

What You're Looking For

The thrust bearings control the crankshaft's forward and rearward movement inside the engine block.

When a thrust bearing begins to fail—or if one is missing entirely—the crankshaft can develop excessive movement.

In severe cases, this movement can often be seen or felt without specialized measuring equipment.

Quick Inspection Procedure

1. Safely raise and support the vehicle.

2. Locate the harmonic balancer at the front of the engine.

3. Apply forward and rearward pressure to the crankshaft.

4. Observe for visible movement.

5. Listen for any noticeable "clunk" or "thunk" as the crankshaft shifts.

A healthy engine should exhibit very little movement.

If obvious movement is present, further inspection is recommended.

What Happens Next?

If excessive crankshaft movement is suspected, a dealership can perform GM's official crankshaft end play measurement procedure.

Those measurements are used to determine whether the engine falls within specification or qualifies for further repairs or replacement.

Checking end play is not a guarantee that a problem exists, nor does the absence of movement guarantee an engine is problem-free. However, it remains one of the best screening tools currently available.

Build Date Matters

One detail that shouldn't be overlooked is the build date of this engine.

This particular vehicle (engine built prior to that) was built in June 2025.

That build timeframe aligns with many of the reported thrust bearing failures that owners have submitted over the past year.

While build date alone does not prove anything, it is another data point that appears to fit the pattern we've been seeing.

As more failed engines are documented, build date information may help narrow down potential production windows associated with these failures.

Why This Finding Could Actually Be Good News

If additional teardowns confirm that missing thrust bearings are responsible for some of these failures, that may actually be positive news for owners.

Why?

Because a missing thrust bearing is a manufacturing assembly issue—not a fundamental design flaw.

Those are two very different problems.

A manufacturing error means engines that were assembled correctly may never experience the issue.

It also means that a simple crankshaft end play inspection could potentially identify affected engines before catastrophic failure occurs.

Again, we are not there yet. More engines need to be inspected before any definitive conclusions can be made.

But if this theory proves accurate, it would significantly narrow the scope of what owners are dealing with.

The Bottom Line

This teardown may represent one of the most important pieces of evidence we've seen so far regarding LZ0 thrust bearing failures.

What was found:

• One damaged thrust bearing

• Excessive crankshaft movement

• A damaged oil squirter

• Insufficient thrust bearing material to account for two installed bearings

• A June 2025 build date that aligns with many reported failures

What remains unknown:

• Whether all failed engines share the same condition

• Whether the missing bearing was a manufacturing error

• Whether the oil squirter played any role in the failure

• Whether multiple failure modes exist

At this point, I'm not prepared to say we've solved every LZ0 thrust bearing failure.

What I am saying is that this engine exhibited the same symptoms we've seen elsewhere, and during teardown, evidence strongly suggested that only one thrust bearing was present.

That finding deserves further investigation.

As more engines are torn down and inspected, we'll continue gathering data and sharing what we find. Every teardown gets us one step closer to understanding what's really happening with these engines.