intheburbs

What a shame. Only GM could take an awesome motor like the 5.3, and crap all over it with this AFM BS.

Get a 3/4-ton with the 6.0. No AFM.

My 08 is at 130,000 miles and still runs like new.

I plan to purchase an 07-08 GM truck for my daughter, and I'm just about 100% sure it won't be an AFM truck.

in2pro

To the best of my knowledge the 6.0 does have the AFM as does the 6.2... government mandates on fuel efficiency pretty much put all auto manufactures over the barrel to do something if they want to continue to use large engines in passenger vehicles and trucks and turning off half the cylinders is the current work around...

Sierra and Yukon V8s Balance Fuel Efficiency, Capability

Dave01

Sorry to hear about your problems. As a 2010 owner stories like yours make me wonder if it will happen to me, have 80,000 on mine.


I've still not seen a definite answer to the question, if you disable AFM are you less likely to have the lifter problems.

in2pro

I have 100,388 on my 2007 and she is still running well...
It happens to a lot of them but not all of them...

intheburbs

Maybe in the half-tons, but not the three-quarter tons. The LY6 in my 08 does not have AFM. And I believe no GMT900 2500 Burbs have AFM, from 07-13.

CAFE does not apply to vehicles with a GVWR above 8500 lbs. So there is no incentive or requirement that the manufacturers make their behemoths more efficient. My 2500 Burb has a GVWR of 8600 lbs.

Which is why I'm leaning towards buying my daughter a 2500 pickup or 2500 Burb, instead of the Avalanche or half-ton pickup.

in2pro

That's all bout to change with with " Phase 2" which will cover medium and heavy duty trucks starting in 2015...
Fuel Economy | National Highway Traffic Safety Administration (NHTSA)


"President Obama directs the National Highway Traffic Safety Administration (NHTSA) and the Environmental Protection Agency (EPA) to develop and issue the next phase ("Phase 2") of medium- and heavy-duty vehicle fuel efficiency and greenhouse gas (GHG) standards by March 2016. Under this timeline, the agencies are expected to issue a Notice of Proposed Rulemaking (NPRM) by March 2015. This second round of fuel efficiency standards will build on the first-ever standards for medium- and heavy-duty vehicles (model years 2014 through 2018)."

Rooti

Update on the turning off of my AFM on my 2007 5.3 silverado....
To refresh your memories I went from 3.42 gears to 4.11 because I'm towing a heavy travel trailer. I had to have the recalibration done afterwards and had it done by a very qualified tuner (Henderson performance) I did not have it dyno tuned but Cory did adjust the original map, recalibrated the speedo and tack, and at the same time turned off the AFM.

Outcome:
Before with the 3.42 gears and the AFM on I averaged a combination of city and highway at 16 MPG. (I don't have a light foot and drive at least 75MPH most of the time on the freeway)
After with the 4.11 gears and the AFM turned off I'm getting exactly the same mileage.

So much for government mandating crap that actually hurts the mileage and messes up your engine. Cory stated that he sees an average of 2MPG more when he turns off the AFM. He states it is counter productive. In other words it burns more fuel going on and off then it would if it never came on.

I paid 100 bucks for the calibration and the ECM tweek. I'm glad I didn't fork over the money for a tuner. For those of you that still have your AFM at stock, I strongly recomend you find a way to shut it off.

in2pro

I don't know if I can buy into the AFM making MPG worse but am glad to hear you had for the most part zero net loss of mpg with the gear swap !

Henderson performance is just down the road from me here in Austin, I might give them a call and see if they can simply turn off my AFM feature..

73shark

There was a lot of anecdotal evidence during the 2007 model year about the 4.10 gears getting better mpg than those with higher gear ratios. The consensus of opinion was that it allowed the engine to operate closer to its sweet spot.

Rooti

I tend to buy onto what cory says. Even the local GM dealership here says whatever Cory says having to do with chevys, you can bet it's true. Try switching back and fourth from 3rd to 4th on the freeway and see if it doesn't affect your mileage.

I have a tendency to believe most of that statement. Once you get over 65 or 70MPH the 4.11 gears are going to suck up more fuel just for the fact the RPM's are higher.
In the city, you get to 4th gear real quick with a light foot and it will still pull most anything in Texas.

Towing my trailer I'm getting 8MPG (7500#'s) but I was pulling a lighter trailer before the 4.11 and only getting 7. I'm expecting better mileage on the freeway. Last trip was all hill country with grades.