Article on AFM delete on GM LS engines

Status
Not open for further replies.
Joined
Dec 31, 2017
Messages
15,073
Location
SE British Columbia, Canada
I noticed a good article on deleting the Displacement On Demand system on the pre-2014 troublesome AFM system on GM LS engines. It's in the Jan 2019 issue of FOUR Wheel and OFF ROAD. Lots of good photos and tips.
 
Last edited:
That pretty much sums it up. The article in the Jan 2019 edition was only four pages long, with some of the same photos. I viewed it on ZINIO.
smile.gif
 
Last edited:
My new gen AFM engines are so seamless you have to use the dash display to know it changed modes
 
One quote in the article was " using the wrong viscosity oil can wreak all kings of havoc. "

The damage to this engine though, was caused be a clogged bleed hole in one of the AFM lifters, which jammed a lifter and bent a pushrod.
 
Originally Posted by Snagglefoot
One quote in the article was " using the wrong viscosity oil can wreak all kings of havoc. "

The damage to this engine though, was caused be a clogged bleed hole in one of the AFM lifters, which jammed a lifter and bent a pushrod.



Said often of the Mopar V8's with dual displacement …
 
Don't want to stir the hornet's nest, but from the 2017 Silverado owners manual the recommended oil vis for the 5.3 and 6.2 V-8's (with AFM) is 0w20.

The recommended oil weight for the good old Gen IV 6.0 (without AFM) is still 5w30.
 
I just bought a 2009 GMC Sierra Z71 with the 5.3L and 152K miles, as a secondary vehicle. It has AFM, but I bought a Range Technology AFM Disable module to disable it. Before that, when I had the Driver Information Center (DIC) set for mileage display, it would also show V4 / V8 mode. I noticed that it would "toggle" between those quite often, and I had some oil consumption. Since I installed the AFM disabler, oil consumption has seemed to decrease. I am using Castrol Magnatec 5W30. I may eventually do the complete delete.
 
Something I noticed in the article that made me curious was waiting until the heads were bolted to the block to change the valve springs. To me it would be a lot easier to take care of that with the heads on a bench.
 
Originally Posted by Auae85
I just bought a 2009 GMC Sierra Z71 with the 5.3L and 152K miles, as a secondary vehicle. It has AFM, but I bought a Range Technology AFM Disable module to disable it. Before that, when I had the Driver Information Center (DIC) set for mileage display, it would also show V4 / V8 mode. I noticed that it would "toggle" between those quite often, and I had some oil consumption. Since I installed the AFM disabler, oil consumption has seemed to decrease. I am using Castrol Magnatec 5W30. I may eventually do the complete delete.


You disabled the function and decreased oil consumption but the suspect parts are still in there with 152K on them. You'll likely go 300k with no problems.
 
Originally Posted by 4WD
My new gen AFM engines are so seamless you have to use the dash display to know it changed modes


I dunno, the LT1 in my Corvette has a noticeable thud. If you run the valved exhaust in the wide-open mode, you can also hear the engine get noticeably quieter.

Then again, it's a Corvette...NVH is a secondary concern. :)
 
Maybe it's different with my LT1 because it's the 8 speed auto, but when mine goes in and out of V4 mode it's barely detectable at all. I have the standard exhaust so it's pretty quiet at cruising speeds already, so you can't even tell based on that. A lot of members of the Corvette Forum believe that AFM is the cause for torque convertor failures on the new Corvette but mine has been flawless so far at just under 8900 miles and I use AFM on a regular basis.
 
Like most magazine articles, Only bits & pieces of it are factual. Snagglefoot.....This following is NOT aimed at you!

*That bent pushrod is from a VVT engine that lost it's Timing Chain Tensioner Spring, It's not even from that engine as the LH6 doesn't have VVT. If the lifter stuck.....The valve would just hang-open a bit & cause low compression on that cylinder. The valves on a LH6 are too small for the pistons to hit them with the stock Cam Timing intact!
Like I stated....This happens to VVT engines & even then, I've never seen it on 3.78" bore VVT engines with lost tensioner springs, ONLY on big valve 4.00" & 4.060" bore VVT engine like the L76 & L99.

*Bad lobe caused by AFM?.....Try again scooter! That's the #8 Intake Lobe, It's NOT an AFM cylinder. Non-AFM engines are afflicted with this as well. Oddly enough.....I've never seen a bad lobe on a AFM cylinder/lobe.

*You "might" get 400hp out of a LH6 with the perfect camshaft selection......That shifts the max HP to about 6,800+rpm & Under the curve torque will be very lacking on your new dyno queen!! Further more, The LH6 like the L33 is a "HO" high compression version of the 5.3L, Most will have a lower compression LMG/LY5 version.



False operational information quoted from the article......
"When the system is activated, solenoids positioned on the underside of the engine valley shut off pressurized oil via special passages to these lifters. This causes the lifter to collapse, allowing the body of the lifter to continue moving up and down with the lobes of the camshaft while the plunger that engages the pushrod remains stationary. "

This is how the AFM Solenoids & Lifters operate in reality......
" The deactivation lifters contain spring loaded locking pins that connect the internal pin housing of the lifter to the outer housing.
The pin housing contains the lifter plunger and pushrod seat which interfaces with the pushrod. The outer housing contacts the camshaft lobe through a roller. During V8 mode, when all cylinders are active, the locking pins are pushed outward by spring force, locking the pin housing and outer housing together causing the lifter to function as a normal lifter. When cylinder deactivation is commanded ON, the locking pins are pushed inward with engine oil pressure directed from the valve lifter oil manifold (VLOM) assembly solenoids. When the lifter pin housing is unlocked from the outer housing, the pin housing will remain stationary, while the outer housing will move with the profile of the camshaft lobe, which results in the valve remaining closed. One VLOM solenoid controls both the intake and exhaust valves for each deactivating cylinder. There are 2 distinct oil passages going to each cylinder deactivation lifter bore, one for the hydraulic lash-adjusting feature of the lifter, and one for controlling the locking pins used for cylinder deactivation."
 
Originally Posted by Patman
Maybe it's different with my LT1 because it's the 8 speed auto, but when mine goes in and out of V4 mode it's barely detectable at all. I have the standard exhaust so it's pretty quiet at cruising speeds already, so you can't even tell based on that. A lot of members of the Corvette Forum believe that AFM is the cause for torque convertor failures on the new Corvette but mine has been flawless so far at just under 8900 miles and I use AFM on a regular basis.



I have a 2018 Silverado with the 5.3 and the six speed. The V4 to V8 change is not noticeable at all.
 
Originally Posted by Snagglefoot
Don't want to stir the hornet's nest, but from the 2017 Silverado owners manual the recommended oil vis for the 5.3 and 6.2 V-8's (with AFM) is 0w20.

The recommended oil weight for the good old Gen IV 6.0 (without AFM) is still 5w30.


The Gen V LT1 calls for 5w30 & uses the exact same AFM hardware as the Ecotech-3 engines......
 
Originally Posted by CKN
Originally Posted by Patman
Maybe it's different with my LT1 because it's the 8 speed auto, but when mine goes in and out of V4 mode it's barely detectable at all. I have the standard exhaust so it's pretty quiet at cruising speeds already, so you can't even tell based on that. A lot of members of the Corvette Forum believe that AFM is the cause for torque convertor failures on the new Corvette but mine has been flawless so far at just under 8900 miles and I use AFM on a regular basis.



I have a 2018 Silverado with the 5.3 and the six speed. The V4 to V8 change is not noticeable at all.


What is noticeable to me … the Silverado does not use V4 as often as the Tahoe … that surprises me being the truck is lighter (it's a SWB regular cab) but has 3:08 gears … Tahoe has 3:42 gears …
 
Status
Not open for further replies.
Back
Top