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Discussion Starter #1
I was running my VIN to see what exactly my truck came with when I noticed this regarding my engine....

LY2ENGINE GAS, 8 CYL, 4.8L, SFI, IRON, CYLINDER DEACTIVATION GM 4.8C W/CYL DEACTVN(LY2)
47,048
I thought active fuel mangement was on the larger V8's or is this something different..it sounds identical?
 

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First off its VORTEC, not trying to be a jerk and yes the 4.8 could be fitted with the GM AFM
 

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Discussion Starter #3
First off its VORTEC, not trying to be a jerk and yes the 4.8 could be fitted with the GM AFM
First off...i know how to spell vortec...sorry I have manly hands and and the x and the c are next to each other. I was going to change it but I couldn't see where I could via the edit post..i really didn't think anyone would get thier panties in a wad over it....but I see there's one in every forum.I was surprised to see that I had that option on my truck as i was told when I bought it that AFM was only available on the 5.3 and 6.0 trucks.
 

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I said not being a jerk, as in ha ha. But yes the 4.8 had/has the AFM option. My simple answer is, tooooo many "dealers" dont understand what they are selling or they dont explain it.
 

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Wow
Surprised GM has added this higher end feature to the 4.8.
It is certainly a good thing-should improve mpg a bit.
What is the EPA on it now?
Before cyl deactivation feature the 5.3 with deactivation was rated about as good as the 4.8.
GM is certainly serious about MPG now-FORD has forced them to get more serious.
The SBs have been pretty efficient for a while now(my 1998 Suburban gets an honest 21 mpg in long-3000 miles-hy trips- but I drive like the old man-60yo-I am-wimpy)
Charlie
Charlie
 

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Wow
Surprised GM has added this higher end feature to the 4.8.
It is certainly a good thing-should improve mpg a bit.
What is the EPA on it now?
Before cyl deactivation feature the 5.3 with deactivation was rated about as good as the 4.8.
GM is certainly serious about MPG now-FORD has forced them to get more serious.
The SBs have been pretty efficient for a while now(my 1998 Suburban gets an honest 21 mpg in long-3000 miles-hy trips- but I drive like the old man-60yo-I am-wimpy)
Charlie
Charlie
Mine has the same code and is a WT. It has a 3.23 rear and the LY2 engine. Short bead and I average around 15 mpg in town and 20 on the highway. I live in Oklahoma so not too many hills and I'm pretty easy on driving. Not to many rabbit starts.
 

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Discussion Starter #8
Wow
Surprised GM has added this higher end feature to the 4.8.
It is certainly a good thing-should improve mpg a bit.
What is the EPA on it now?
Before cyl deactivation feature the 5.3 with deactivation was rated about as good as the 4.8.
GM is certainly serious about MPG now-FORD has forced them to get more serious.
The SBs have been pretty efficient for a while now(my 1998 Suburban gets an honest 21 mpg in long-3000 miles-hy trips- but I drive like the old man-60yo-I am-wimpy)
Charlie
Charlie
I get 14 in town all day and I am heavy footed. I have gotten 15 in town but thats hard to do just becasue of my heavy foot. I dont get nearly what icemncmth gets on the freeway...I maybe get 17 doing 80-85 mph.
 

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I get 14 in town all day and I am heavy footed. I have gotten 15 in town but thats hard to do just becasue of my heavy foot. I dont get nearly what icemncmth gets on the freeway...I maybe get 17 doing 80-85 mph.
What rear gears does yours have? Also you have two more doors than I.

---------- Post added at 02:28 PM ---------- Previous post was at 02:19 PM ----------

I said not being a jerk, as in ha ha. But yes the 4.8 had/has the AFM option. My simple answer is, tooooo many "dealers" dont understand what they are selling or they dont explain it.
I will say that my father n law does have AFM and I have driven his a ton. My truck vs his Tahoe driving wise and his has the same little "quirks" as mine. You will feel a rough idle and on the highway if I have cruise on either vehicle and you put your foot to the floor it does seem to take a few seconds for the system to wake up. A buddy's truck without AFM doesn't hesitate. Mines sometimes feels like it needs a few seconds to figure out what you really want.

Now I do think GM's cruise system needs to be tweaked because it doesn't hold a candle to most of the imports. A tundra I drive at work will hold the speed within a 3 mph and most of the GM vehicles seem to float a little too much going down hill.
 

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"I maybe get 17 doing 80-85 mph. "

sstoner911- 80-85mph!! Hah, if I pushed the old 5.7 Suburban to 85 mph it would probably get 14 mpg or so. 17 mpg at 80 mph is pretty darned good!!
When we drive from New Orleans to Flagstaff AZ I drive like a wimp-slowly!!
I set the CC to 67mph but drop to 45 mph for roadwork, 35-45 mph thru cities small towns,and 58 mph for 350 miles of Hy 287.
I would guess my average driving speed is more like 60-62 mph-takes~ 71 gallons to do 1510 miles.2 adults, 1-2 greyhounds, double bed mattress, ,ice chest and bike in hitch mounted basket.

You guys are geared pretty tall-3.23- How many RPMS at 60 mph?
I think I have a 3.42- turns 1720 rpms at 60 mph-tiny 15" wheels 235/75 15

The cyl shutdown is a pretty good idea, but it probably would work better if you drove like a wimp-60-65 mph or so.When you get older your right foot will become lighter!!
 

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Discussion Starter #11
What rear gears does yours have? Also you have two more doors than I.

---------- Post added at 02:28 PM ---------- Previous post was at 02:19 PM ----------



I will say that my father n law does have AFM and I have driven his a ton. My truck vs his Tahoe driving wise and his has the same little "quirks" as mine. You will feel a rough idle and on the highway if I have cruise on either vehicle and you put your foot to the floor it does seem to take a few seconds for the system to wake up. A buddy's truck without AFM doesn't hesitate. Mines sometimes feels like it needs a few seconds to figure out what you really want.

Now I do think GM's cruise system needs to be tweaked because it doesn't hold a candle to most of the imports. A tundra I drive at work will hold the speed within a 3 mph and most of the GM vehicles seem to float a little too much going down hill.
"I maybe get 17 doing 80-85 mph. "

sstoner911- 80-85mph!! Hah, if I pushed the old 5.7 Suburban to 85 mph it would probably get 14 mpg or so. 17 mpg at 80 mph is pretty darned good!!
When we drive from New Orleans to Flagstaff AZ I drive like a wimp-slowly!!
I set the CC to 67mph but drop to 45 mph for roadwork, 35-45 mph thru cities small towns,and 58 mph for 350 miles of Hy 287.
I would guess my average driving speed is more like 60-62 mph-takes~ 71 gallons to do 1510 miles.2 adults, 1-2 greyhounds, double bed mattress, ,ice chest and bike in hitch mounted basket.

You guys are geared pretty tall-3.23- How many RPMS at 60 mph?
I think I have a 3.42- turns 1720 rpms at 60 mph-tiny 15" wheels 235/75 15

The cyl shutdown is a pretty good idea, but it probably would work better if you drove like a wimp-60-65 mph or so.When you get older your right foot will become lighter!!
I actually changed my gears from 3.23 to 4.11s! My tires are Toyo Proxies II 305/45/22.

I am not to concerned about my gas mileage....its decent but you always want to do better!

At 85mph I am running 2500 rpm's.
 

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sstoner911
14 in town and 17 hy(at 80 or so) is pretty good MPG for a 1/2 ton V-8 pickup.
GM has done a good job FE wise with their SBCs
Charlie
PS I used to be surprised that the 2 valve pushrod motors generally match and beat the "more modern" 4 valve OHC motors in respect to part throttle FE, and they more or less match the HP Torque.Guess GM knows how to max FE.
 

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Where do you look up this information? I want to know what gears are in my rear end. >.<

And i also find myself getting better MPG when i'm going 85 here in TX...
 

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Ridyn
Look at the inside of your glove box door.
It will have maybe 60-80 codes- 3 character codes.

Google GM differential codes- you will find many sites with that info. You could just search GM build codes(you don't want error codes)
From memory my 3.42 is GU6.
Charlie
 
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