question on MPG before and after AFM delete

[harbison]

I have experienced AFM lifter failure FOUR times! First time was at 124,000 miles (slightly out of the 120,000 mile limit). No help from GM. Replaced failed lifter on 4. Next failure was on 1. Replaced all four lifters on 1 and 7. Next failure was on 6. Replaced all four lifters on 4 and 6. Thought I was in the clear since all eight AFM lifters had been replaced and Range Disabler was installed. Nope. Replacement lifter on 7 failed at 200,000 miles last week. Going to get AFM Delete Tune now. Range Disabler is not 100% reliable in turning off AFM. Gas mileage is not the point here. I have noticed little to no change. V4 only occurs when you're coasting downhill. But even if it did cost you a mile or two of mpg, you would never come out ahead.
Head gasket kit - $250; Lifters - $45-55 each; plus Oil change and Antifreeze. And that's with my free labor. Took me about 7 hours this last time. First time took about two days. I'm getting better with experience but trust me I don't want this kind of experience. Also had to rent a car for my wife in the meantime.
This is a one owner vehicle. So I know it's entire history. Never been abused. Always been maintained well. It's always used oil. Since first lifter failure I've ignored the Engine Oil Life suggestion which is 8,000 miles or more. I've changed the oil every 3,000 miles. I know the oil can go longer than that but with the oil consumption problem and the extremely tight tolerance inside the AFM lifters I don't want to take any chance with dirty oil. Oil is a lot cheaper than an engine.
I would GLADLY give up a little mpg to avoid such a headache!
5.3 is a good engine but the AFM lifters are a mistake.

 

[PG01]

Wow, thats a first......

 

[iamdub]

Range Disabler is not 100% reliable in turning off AFM.

That's a first that I've heard of the Range not being 100% reliable in turning off AFM. I thought either it keeps AFM from engaging or it doesn't (defective). Unless you have a defective unit that only works intermittently and the few times it was plugged in but not working was enough to let AFM activate and ultimately lead to your failures.

I'm more inclined to believe that the failures aren't from the Range, but from the lifters themselves. You should delete AFM rather than just disable it. A tune would disable AFM just as the Range does, but the mechanical components- the unreliable lifters, are still there. I believe disabling AFM via tune or Range just buys time.

 

[harbison]

Wow, thats a first......

Yeah, first fool who would fix it that many times! We've driven over half a million miles in the four Suburban/Yukons we've owned in the past twenty years (93, 99 Suburbans, 01 Yukon Denali XL, 09 Yukon XL). This is the only one that has ever had any drive train issues. We have three kids in high school and one in college and drive 25-30K per year. Nothing else really fits our family comfortably. Even as much trouble as it is, it's still cheaper than a car payment. In a few years we'll probably switch to a smaller non-GM SUV.

 

[harbison]

That's a first that I've heard of the Range not being 100% reliable in turning off AFM. I thought either it keeps AFM from engaging or it doesn't (defective). Unless you have a defective unit that only works intermittently and the few times it was plugged in but not working was enough to let AFM activate and ultimately lead to your failures.

I'm more inclined to believe that the failures aren't from the Range, but from the lifters themselves. You should delete AFM rather than just disable it. A tune would disable AFM just as the Range does, but the mechanical components- the unreliable lifters, are still there. I believe disabling AFM via tune or Range just buys time.

There are a few times that I have caught the Range not working, very few but a few. You are correct that the real problem is unreliable lifters. But if AFM is never called for, then the lifter never collapses and never has a chance to stick.

I checked with an engine builder who does a true AFM delete by changing the camshaft and replacing AFM lifters with non-AFM lifters as well as AFM delete tuning. However, the cost was almost as much as a replacement engine.

 

[conchasjim]

I guess I should knock on wood. None of these issues with my 07 with the 5.3. My only complaint is it doesn't tow worth a shit. I attribute that to the 3:43 rear end. I'm looking to change to 3:73 and see what that does. Anyone tried it?

 

[iamdub]

I guess I should knock on wood. None of these issues with my 07 with the 5.3. My only complaint is it doesn't tow worth a shit. I attribute that to the 3:43 rear end. I'm looking to change to 3:73 and see what that does. Anyone tried it?

*3.42

Mine has the 3.73, but I've never towed more than a 5'x8' expanded metal trailer with maybe 200lbs on it. I think it should have more off-the-line pull towing or not. But, I think that's from the conservative Torque Management tuning.

 

[NGAneer]

I had improved MPG from my BB tune which removed my AFM among other things. I went from 11 city, 17hwy to 13 city, 20 hwy with the tune. All numbers with same suspension/tire combination.

Sent from my VS835 using Tapatalk

 

[992dr]

I guess I should knock on wood. None of these issues with my 07 with the 5.3. My only complaint is it doesn't tow worth a shit. I attribute that to the 3:43 rear end. I'm looking to change to 3:73 and see what that does. Anyone tried it?

I will agree with you there and I have 3:73s.
What are you towing?
My only towing experience was with an 18' enclosed trailer empty one way and with my 54" tool box on the way home. It weighs about 600lbs. It was a dog both ways.

Mine is pretty much stock besides the tune and 2800/3000 billet stall and a shift kit jr.

My previous 992dr had a built trans 3200 billet stall, intake and full exhaust and that sucker would pull until the tires would burn off hahaha.

 

[PG01]