Potential Lifter Issue Post Factory “Fix”

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Geotrash

Dave
Supporting Member
Joined
Feb 16, 2018
Posts
5,867
Reaction score
14,206
Location
Richmond, VA
A lifter is such a simple device. A pushrod engine is stupid simple. This isn't rocket science.
It’s true. A standard hydraulic roller lifter is a simple device. But DFM lifters are not simple devices, nor is the system of electro-mechanically controlled hydraulics that operates them.
 

DuraYuk

Full Access Member
Joined
Sep 17, 2022
Posts
813
Reaction score
590
It’s true. A standard hydraulic roller lifter is a simple device. But DFM lifters are not simple devices, nor is the system of electro-mechanically controlled hydraulics that operates them.
Its actually incredibly simple. Ecm sends signal to solenoid. Solenoid either allows the lifter to fully engage or gets by passed for active/dynamic fuel management to take place. This isn't rocket science.

If you think this is some crazy tech on the prehistoric pushrod v8 good for you. But it's not.
 

BlaineBug

Full Access Member
Joined
Dec 29, 2019
Posts
1,157
Reaction score
659
Location
Clown World
Don't these "new" motors with active fuel management have twice as many AFM lifters as previous gen with dynamic fuel management which also only had 4?
 

Blackcar

Full Access Member
Joined
Mar 31, 2018
Posts
684
Reaction score
590
May not be rocket science but most repair parts are made by outsourced company's which makes quality control a problem. If I understand when suppliers part causes problem they are responsible for cost of parts and repair which in turn alot of times in big recall or problem bankrupts said supplier.
Now if problem raises its head after power train warranty they expect as I have been reading owners to pay half of repair when they are being if I understand agreements with suppliers reimburse by supplier, so in my view they are making money on repairs.
Also, techs don't get paid going shop rate for warranty repairs and parts are provided at wholesale. So, this repair does not cost GM a whole lot just reputation to brand. Just my view to repair under so called goodwill.
 

Geotrash

Dave
Supporting Member
Joined
Feb 16, 2018
Posts
5,867
Reaction score
14,206
Location
Richmond, VA
Don't these "new" motors with active fuel management have twice as many AFM lifters as previous gen with dynamic fuel management which also only had 4?
Yes that’s correct, but you just have the terminology reversed. DFM is the current generation, and AFM is the previous generation.
 

Geotrash

Dave
Supporting Member
Joined
Feb 16, 2018
Posts
5,867
Reaction score
14,206
Location
Richmond, VA
Its actually incredibly simple. Ecm sends signal to solenoid. Solenoid either allows the lifter to fully engage or gets by passed for active/dynamic fuel management to take place. This isn't rocket science.

If you think this is some crazy tech on the prehistoric pushrod v8 good for you. But it's not.
Roller lifter riding on a cam = simple

Roller lifter where the top half rotates 90° + 16 oil control solenoids + wiring + electronics + thousands of lines of code to control it in response to inputs from crank, cam, throttle position, and vehicle speed sensors plus other vehicle status data = not simple.
 

DuraYuk

Full Access Member
Joined
Sep 17, 2022
Posts
813
Reaction score
590
Roller lifter riding on a cam = simple

Roller lifter where the top half rotates 90° + 16 oil control solenoids + wiring + electronics + thousands of lines of code to control it in response to inputs from crank, cam, throttle position, and vehicle speed sensors plus other vehicle status data = not simple.
You can cut it up any which way but it's very simple in operation.

A dohc motor with vvti is way more complex then a pushrod v8 with dfm. And even those are simple.

These engines are ancient. If you really think that dfm makes them complex that's exactly what GM hopes for because the v8s they have are stupid old and stupid simple..for some that's an advantage for others it's a sour point.
 

Geotrash

Dave
Supporting Member
Joined
Feb 16, 2018
Posts
5,867
Reaction score
14,206
Location
Richmond, VA
You can cut it up any which way but it's very simple in operation.

A dohc motor with vvti is way more complex then a pushrod v8 with dfm. And even those are simple.

These engines are ancient. If you really think that dfm makes them complex that's exactly what GM hopes for because the v8s they have are stupid old and stupid simple..for some that's an advantage for others it's a sour point.
We’re not talking about cam phasers. We’re talking about the design of the DFM system and its complexity relative to the simple roller lifter system of pre-AFM engines. You were trying to make the case that it’s not a complex system, and I’m disagreeing with you on that point. Further, that because of it there is a substantially higher probability of failure as a function of both design and the manufacturing challenges inherent to it. And, others here are arguing quite rightly that the problem is widespread relative to any other potential problems with these trucks. Only a small portion of those stories are being told here.

I don’t see how anyone could honestly argue otherwise without access to the incidence data.
 

DuraYuk

Full Access Member
Joined
Sep 17, 2022
Posts
813
Reaction score
590
We’re not talking about cam phasers. We’re talking about the design of the DFM system and its complexity relative to the simple roller lifter system of pre-AFM engines. You were trying to make the case that it’s not a complex system, and I’m disagreeing with you on that point. Further, that because of it there is a substantially higher probability of failure as a function of both design and the manufacturing challenges inherent to it. And, others here are arguing quite rightly that the problem is widespread relative to any other potential problems with these trucks. Only a small portion of those stories are being told here.

I don’t see how anyone could honestly argue otherwise without access to the incidence data.
We are not talking about cam phasers. You are arguing that somehow a dfm lifter is some complex mechanism when it is not. Having more lifters a few more oil passages and a solenoid to direct action is simple stuff.

I used to be a tech and am a mechanical engineer. Maybe for me it is but you see it as some complex mechanism.

Im not making excuses for why it fails. It's a supplier issue that does not affect even remotely all the vehicles with these engines.

The GM pushrod v8 with dfm is stupid simple and one of the most archaic drive trains out there. I don't think you quite understand vehicle systems if you are arguing that it's complex.

Regardless i will leave the argument here.

Its almost better not to comment I suppose.
 

Geotrash

Dave
Supporting Member
Joined
Feb 16, 2018
Posts
5,867
Reaction score
14,206
Location
Richmond, VA
You are arguing that somehow a dfm lifter is some complex mechanism when it is not. Having more lifters a few more oil passages and a solenoid to direct action is simple stuff.
No sir. I’m arguing that the DFM *system* is complex and accordingly more vulnerable to manufacturing defects, demands more from the collapsible lifters than the previous AFM system due to how frequently it engages and disengages, and that it’s proving problematic enough as a system for enough people, to be a valid reason for me to avoid buying a DFM equipped truck until they sort it out. And that people are justified in being upset about it and in feeling unable to trust their vehicles.
 

Forum statistics

Threads
130,407
Posts
1,832,042
Members
94,019
Latest member
Samuel t1
Top