NHTSA opens preliminary probe into more than 870,000 GM vehicles

[jfoj]

Pumps are not interchangeable but you'd think they were looking at them. Both are "2 stage" as in they're both variable geometry pumps. GM does reference the L84 as "single stage" but it's more marketing than anything else. In theory they're infinitely variable but GM only uses a binary high output and "low" output via the solenoid.

A variable displacement pump is what both the L84 5.3l and L87 6.2l engines have, but a variable displacement pump is not functioning as a 2 stage pump. The "2 stage" pump uses an electrically operated solenoid to likely bleed off oil/oil pressure back into the sump when engine conditions are not requiring as much oil pressure/volume. This is likely why there are 2 different oil pump part numbers, one likely with a 2 stage solenoid and one likely without the 2 stage solenoid. It may be possible that the 2 stage solenoid is not a serviceable part by itself as I have not been able to find one.

For reference, for the previous generation 5.3l L83 and 6.2l L86 they actually did use the same oil pump based on part numbers I have found and I believe both these engines had the 2 stage oil pump solenoid.

All the research I have done and it has been quite a bit indicates that the current generation L84 5.3l engine does not have the 2 state ECM controlled solenoid like the L87 6.2l currently has. As mentioned, research seems to indicate that the previous generation L83 5.3l engine did have the 2 stage oil pump that was ECM controlled.

 

[blanchard7684]

Ended up placing an order today for a 2025 F150 Lariat with the 5.0 with Granger Ford because it seems GM has been unable to resolve the problems with its NA V8s after 5+ years.

Maybe they will work it out on their next gen V8s.

I don't have a dog in your particular hunt...but FYI I have a 2025 f150 for work with 5.0 and it is terrible. outside of wide open throttle, the engine and transmission mapping are nauseating, it feels like a 1980s truck with a carburetor way out of adjustment and a bad secondary ignition system problem.

I would drive one before you take delivery.

 

[blanchard7684]

LSPI really isn't an issue with atmospheric engines. Forced induction different story.

Forced induction a pre-ignition issue can cause engine failure in a few hundred rotations of crankshaft. An NA engine it can still cause damage but over a longer period of time.

Current engine controls are very good at detecting and mitigating it.

The question is if low engine speed pre ignition is more prevalent on 6.2 vs 5.3.

 

[Polo08816]

I don't have a dog in your particular hunt...but FYI I have a 2025 f150 for work with 5.0 and it is terrible. outside of wide open throttle, the engine and transmission mapping are nauseating, it feels like a 1980s truck with a carburetor way out of adjustment and a bad secondary ignition system problem.

I would drive one before you take delivery.

Out of curiosity, does your work truck have 3.31 rear end or the 3.73 - I know there's the 8.8" and the 9.75" variant diffs.

We test drove the Sierra 1500 SLT with the LZ0 and 6.2L - once each.

We test drove the 2024 F150 5.0 and the 2025 F150 5.0 (Job 1) as well.

GM's transmission programming was better than both, but the 2024 F150 was more clunky than the 2025 F150. I would imagine that it's harder to re-program a shift strategy in the middle of a MY because it may impact EPA ratings.

The 2025 F150 5.0's transmission was acceptable and this is coming from someone who has 2 vehicles with the ZF 8HPXX series transmissions. I think the mechanical flaws with these transmissions have been worked out at this point with the TSBs that were released in 2023 and 2024.

In many respects the Sierra 1500 were more polished but it had 2 critical deficiencies. First, the potential L84/L87 design flaw with its lifters/DOD system coupled with the 3+ month backorder of L87 engines AND the 24 gallon gas tank.

I just simply wouldn't consider a turbodiesel powertrain over a naturally aspirated gas powertrain for 1/2 ton use because we keep our vehicles 6-12 years. Complexity is usually at the expensive of reliability.

 

[blanchard7684]

Out of curiosity, does your work truck have 3.31 rear end or the 3.73 - I know there's the 8.8" and the 9.75" variant diffs.

We test drove the Sierra 1500 SLT with the LZ0 and 6.2L - once each.

We test drove the 2024 F150 5.0 and the 2025 F150 5.0 (Job 1) as well.

GM's transmission programming was better than both, but the 2024 F150 was more clunky than the 2025 F150. I would imagine that it's harder to re-program a shift strategy in the middle of a MY because it may impact EPA ratings.

The 2025 F150 5.0's transmission was acceptable and this is coming from someone who has 2 vehicles with the ZF 8HPXX series transmissions. I think the mechanical flaws with these transmissions have been worked out at this point with the TSBs that were released in 2023 and 2024.

In many respects the Sierra 1500 were more polished but it had 2 critical deficiencies. First, the potential L84/L87 design flaw with its lifters/DOD system coupled with the 3+ month backorder of L87 engines AND the 24 gallon gas tank.

I just simply wouldn't consider a turbodiesel powertrain over a naturally aspirated gas powertrain for 1/2 ton use because we keep our vehicles 6-12 years. Complexity is usually at the expensive of reliability.

it is 3.31

 

[Polo08816]

it is 3.31

I think that would impact perceived performance, but I don't think the 3.73 will fully resolve what you're experiencing.

I was willing to accept a less than optimal shift strategy as long as it didn't affect reliability/durability. The alternative was an engine with a possible propensity to have parts from the bottom end "hatch" out of the side of the engine block.

Going the pickup (F150) route will impact our future car purchase selection though. We were considering a full size SUV before going with the pickup, but the price for these new Expeditions / Suburbans were just too high for not needing the passenger space at the moment. Now that we will have a large vehicle to do the hauling/towing, it gives us more flexibility with our replacement SUV to something smaller like a Ford Explorer, Toyota 4Runner, or Lexus GX550.

 

[cjlewis]

GM Can’t Keep Up With 6.2L V8 Engine Replacements​

https://gmauthority.com/blog/2025/02/gm-cant-keep-up-with-6-2l-v8-engine-replacements/

 

[Polo08816]

GM Can’t Keep Up With 6.2L V8 Engine Replacements​

https://gmauthority.com/blog/2025/02/gm-cant-keep-up-with-6-2l-v8-engine-replacements/

That was one of my fears... and why we switch to the Ford F150 5.0 last minute.

 

[blanchard7684]

I think that would impact perceived performance, but I don't think the 3.73 will fully resolve what you're experiencing.

I was willing to accept a less than optimal shift strategy as long as it didn't affect reliability/durability. The alternative was an engine with a possible propensity to have parts from the bottom end "hatch" out of the side of the engine block.

Going the pickup (F150) route will impact our future car purchase selection though. We were considering a full size SUV before going with the pickup, but the price for these new Expeditions / Suburbans were just too high for not needing the passenger space at the moment. Now that we will have a large vehicle to do the hauling/towing, it gives us more flexibility with our replacement SUV to something smaller like a Ford Explorer, Toyota 4Runner, or Lexus GX550.

Fair point.

 

[jfoj]

The question is if low engine speed pre ignition is more prevalent on 6.2 vs 5.3.

Do not know about the 5.3l engine loading, but after my 2 hour drive today monitoring the engine RPM and ECM % Load I was shocked. The 6.2l is like a Diesel engine, a torque monster. What I found is the engine RPM even at 85 MPH is only 1840 RPM. While cruising at one point around 75 MPH with the engine RPM at around 1620 RPM and climbing a slight grade, I watched the engine Load % go up to as high as 85% without the transmission ever downshifting. What I am finding is approximately 70% of time during highway cruising the 6.2L operates at or above 50% Load based on the ECM values, rarely does the transmission downshift unless trying to moving around traffic, but if on cruise control, the transmission rarely downshifts.

Not sure if the 5.3l is has more active transmission downshifting due to its lower torque output?

The conclusion I am quickly coming to is the 6.2l with the 2 stage oil pump and running 0W20 oil and the engine loading that I am seeing, if you are not running Premium fuel and even if you are, the engine may have conditions for LSPI and the bearing loading will be very high.

I am thinking the majority of the 6.2l problems are from lower oil pressure due to the 2 stage oil pump (around 45 PSI at 75 MPH at 1600 RPM) causing oil starvation when running 0W20 engine oil. With the constant high loading on the bearings, this does not seem like there will be a good outcome. This along with the conditions with a NA engine for LSPI that could start to hammer bearings in these engines. High loading under low RPM and thin oil that is being washed in the cylinders and if the engine has higher oil consumption, this is really a bad situation.

Some initial feedback I am getting is a similar 5.3L L84 configured vehicle has close to 60 PSI oil pressure at 1500 RPM while cruising on the highway. The 5.3l likely would not be constantly operating such high engine loading due to the lower torque output. Assuming the transmission on the 5.3l may be downshifting more often than a similarly configured 6.2l vehicle.