Xfe On A 2008? 6 Cyl Transmission?

[wescollins]

The XFE didn't come out until '09 right? My '08 keeps saying its in 4 cyl mode when going down hill or easy driving and the "instant" mpg goes up. Is it just a computer thing? It was actually mfg'ed in early '08.

 

Also, they still had the 4 speed trannies right? I was getting ready to change out the tranny/transfer case fluid and it lists the 6 speed in the '08 manual as optional for some reason.

 

How do I tell what tranny I have?

 

This says the dexron VI in both the transfer case and tranny. Is that right? It has the "auto" 4wd mode. Thanks for the help!

[MS3DALE]

The 4 cyl. mode is the AFM or "Active Fuel Management"

Your '08 would have the 4L60E 4-speed transmission - RPO "M30" (Unless you have the 6.0 which would have the 4L70E - RPO "M70")

And yes,Use Dexron VI in both the transmission and transfer-case.

 

BTW...The 6-spd. transmission the manual is talking about is either the 6L80E or the 6L90E thats in the Denali's/Escalade's/2500HD's/3500HD's.

 

Oh....The "XFE" models are 2wd only,You cannot get a 4wd XFE.

[wescollins]

Thanks.

 

So it does actually have active fuel management? Cool, thought that was only on the XFE models.

 

its the 5.3L, Z71 4wd, 3.73 gears, LT model with leather bucket seats, fold-in signal mirrors, G80 rear end, I guess it was probably special ordered, I didn't get it new. Had 18k on it.

[MS3DALE]

Thanks.

 

So it does actually have active fuel management? Cool, thought that was only on the XFE models.

 

Yes,and no It does have AFM,and its not only on the XFE models.

[trucc_boi]

dont all nnbs 5.3's have AFM? unless they have been tuned to turn it off.

 

why dont they put AFM on the 4.8's or even the 4.3's?

[Sir Dan]

dont all nnbs 5.3's have AFM? unless they have been tuned to turn it off.

 

why dont they put AFM on the 4.8's or even the 4.3's?

Probably because it's doesn't do any good for gas mileage anyway and prompts more complaints than its worth. AFM was mostly a sales gimmick and only helps your mileage like .25 mpg. For me its not worth the engine hesitation and jerky throttle response for that little bit so mine is turned OFF.

Oh and yes, all 5.3s in full size truck models have AFM.

[caddycruiser]

dont all nnbs 5.3's have AFM? unless they have been tuned to turn it off.

 

why dont they put AFM on the 4.8's or even the 4.3's?

Probably because it's doesn't do any good for gas mileage anyway and prompts more complaints than its worth. AFM was mostly a sales gimmick and only helps your mileage like .25 mpg. For me its not worth the engine hesitation and jerky throttle response for that little bit so mine is turned OFF.

Oh and yes, all 5.3s in full size truck models have AFM.

 

 

The "problems" part isn't really true. It doesn't help much, but it definitely helps some. It would just help if things were tuned to operate a little more effectively right from the get go, 8-cyl and 4-cyl modes. Did make for some buzzes & such in some vehicles, but not the majority. Otherwise it wouldn't be there.

 

Custom tune done for my G8 GT with the AFM 6.0L, for 93 octane and making AFM active more often, and there were times when I could cruise to work & back and be in 4-cyl mode most of the time. The 6.0L's extra torque to begin with helped here, and made for great mileage at those times, another reason why the Hybrid trucks were based on using the 6.0L.

 

It all depends. Just like with the G8, Camaro, etc. most don't even notice the AFM system on/off, but some vehicles have issues, like anything else. Start modifying intake/exhaust, and it also gets more noticeable. Whether it's truly effective enough to be worth it is another matter.

 

Back to the original topic, all 5.3L full size trucks have had it, like said, since the redesign. Same for the trans change already described. XFE differences are tuning, tires, and some extra aluminum bits & lower ride height. Otherwise all the same mechanicals.