GM Redesigns the 3.0 Duramax Engine Oil Pan (LM2) (LZ0)
- Greg Nelson
- 2 minutes ago
- 3 min read
New Part # 40009800 Replaces # 55506665
GM has quietly rolled out a redesigned engine oil pan for the 3.0L Duramax diesel (LM2 + LZ0) — and the changes are more significant than they first appear.
I came across this updated design while replacing an LM2 in a 2020 Silverado. At first glance, the drain plug location caught my attention. But once the pan was off and sitting next to the original design, it became clear: this is more than a minor revision.
Let’s break down what changed — and what it likely means for owners.
Old vs. New Oil Pan Design
1. Drain Plug Relocation
The most noticeable change is the drain plug position.
On the original pan (# 55506665), the drain plug was not located at the absolute lowest point of the sump. As a result, a measurable amount of oil remained trapped inside after draining. If you've ever removed one of these pans, you know exactly how much oil can sit in that lower pocket.
The new design (# 40009800) moves the drain plug to the true low point of the pan.
Why this matters:
More complete oil drainage during service
Less residual oil mixing with fresh oil
Potentially cleaner oil changes over time
It still won’t be a 100% perfect drain — there’s still a stepped section inside the sump — but it is unquestionably an improvement over the original design.
2. Revised Internal Sump Geometry
Inside the new pan, there is a noticeable “step” and recessed pocket area.
At first glance, it looks like sump volume was reduced in one area. However, GM appears to have compensated by expanding the outer perimeter of the pan, reclaiming what was previously unused space.
The net result appears to maintain similar oil capacity while improving oil control and drainage characteristics.
Why the internal change?
Possible explanations:
Oil control refinement
Pickup optimization
Windage/aeration management
Preparation for upcoming platform updates
Until GM publishes specific engineering notes, we can only speculate — but it does not appear accidental.
3. New Oil Pickup Tube Design
The new oil pan comes with a matching pickup tube — and it is not interchangeable with the original.
The revised pickup features:
A straighter entry angle
A scoop-style inlet
A changed mounting orientation
The original pickup had a more angled design, which confirms the pickup location within the sump has shifted.
Important:These pans are not directly swappable without the correct pickup tube. If you’re ordering parts, make sure you’re getting the proper matched setup for your engine configuration.
4. Added Structural Tabs
The new pan features multiple small exterior tabs that were not present on the original design.
Their exact purpose isn’t officially documented, but they could assist with:
Alignment during installation
Structural reinforcement
Ease of removal
Regardless of purpose, it’s another indicator that this was a thoughtful redesign — not just a casting tweak.
5. Improved Factory Drain Plug
GM also upgraded the drain plug itself.
The new plug features:
A taller head profile
Easier tool engagement
Slightly improved serviceability
It’s still not perfect, but it’s better.
That said, I still recommend a high-quality aftermarket magnetic drain plug. The stronger magnet and taller head design make servicing easier and provide an extra layer of monitoring for internal wear.
Aftermarket Compatibility: PPE Oil Pan Question
One open question is how this new factory design Pickup interacts with aftermarket oil pans like those from PPE.
Because the pickup location and sump geometry have changed, fitment may vary depending on which factory configuration your truck has.
If you’re planning an upgrade:
Verify which pan is currently on your truck
Confirm pickup compatibility
Double-check part numbers before ordering
Until confirmed otherwise, caution is advised when mixing early and late-style components.
Why Did GM Make This Change?
While GM has not publicly detailed the reason, here are the most logical explanations:
Improve oil change effectiveness
Optimize pickup location
Refine oil control under load
Prepare for upcoming model year updates
Given how much residual oil the original pan retained, the drain relocation alone justifies the revision.
This feels like a genuine step forward.
Part Numbers
NEW Oil Pan: 40009800
OLD Oil Pan: 55506665
If you’re servicing or replacing an LM2, verify which design you have before ordering.
From a technician’s perspective, this redesign makes sense.
Better drainage.
Updated pickup design.
Improved drain plug.
Refined sump geometry.
It’s not revolutionary — but it’s meaningful.
And on an engine like the 3.0 Duramax, small refinements over time add up.
If you’ve encountered this new pan in the wild, I’d be interested to hear your experience.
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