Nbs Or Vmax Owners

2007VMAX · June 26, 2007

Does anyone else feel their truck make the change between V4&V8 mode? While cruising down the highway I was noticing the truck would almost feel like it had split second hesitation every once in a while. I put the displacement mode up and it would do it every time the mode indicator would switch between V4&V8. I never noticed it in my wifes 07 Tahoe 5.3. My truck only has about 300 miles on it so maybe this has something to do with it. It's a VMAX with 4.10 gears just curious if anyone else noticed this?

VMax2007 · June 26, 2007

Does anyone else feel their truck make the change between V4&V8 mode? While cruising down the highway I was noticing the truck would almost feel like it had split second hesitation every once in a while. I put the displacement mode up and it would do it every time the mode indicator would switch between V4&V8. I never noticed it in my wifes 07 Tahoe 5.3. My truck only has about 300 miles on it so maybe this has something to do with it. It's a VMAX with 4.10 gears just curious if anyone else noticed this?

Mine is a Vmax with 3.73's. I never notice it at all, it has 3000 miles now, but I didn't notice it at 300 miles either. Make sure what your "feeling" isn't TM though, that does create a slight hesitation when accelerating, especially when downshifting. Also, keep in mind my truck with 3.73s rarely stays in V4 mode unless I am decelerating or have the cruise on and the freeway is completely level. My truck actually uses V4 mode more while towing my 3000 lb boat and using Tow/Haul mode because it keeps the RPMs higher. Your truck with 4.10s probably uses V4 mode on the freeway more than mine due to higher RPMs and more available power.

2007VMAX · June 26, 2007

I don't think it's TM it does it only when it is changing cylinder modes? Yes it does use V4 mode quite often when traveling on the highway.

GeoHawk · June 26, 2007

I can't feel the switch in mine. Other than the DIC the only way I can tell the switch is the different exhaust sound. My truck did kind of run like crap for the first few hundred miles or so. Must have just been the ECM "learning" or something. It's butter smooth now.

redsled2007 · June 26, 2007

Does anyone else feel their truck make the change between V4&V8 mode? While cruising down the highway I was noticing the truck would almost feel like it had split second hesitation every once in a while. I put the displacement mode up and it would do it every time the mode indicator would switch between V4&V8.

The way the V4/V8 mode works is every 8 secs it changes the 4 cyclinders that are operating. This is to keep the bearings from becoming damaged after long periods of V4 usage. But I haven't felt any hesitation that you discribe.

GeoHawk · June 26, 2007

Actually it looks like there is a TSB for this condition. I'd wait a few hundred more miles to see if things smooth out, but if it's still doing it take it in to have the ECM/TCM reprogrammed:

Document ID# 1969002

2007 Chevrolet Silverado - 4WD

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Subject: L76 4L60-E, 4L70-E Chuggle, Surge or Hesitation May be Felt with Active Fuel Management System Cylinder Deactivation Transition from V8 Mode to V4 Mode (Reprogram ECM and TCM) #07-06-04-013 - (05/04/2007)

Models: 2007 Chevrolet Avalanche, Silverado, Suburban, Tahoe

2007 GMC Sierra, Yukon, Yukon XL

with Active Fuel Management System Vortec® GEN IV 6.0L V8 Engine (VIN Y -- RPO L76)

and

HYDRA-MATIC® 4L60-E, 4L70-E Transmission (RPOs M30, M70)

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Condition

Some customers may comment on a chuggle, surge or hesitation felt during an Active Fuel Management System (AFM) cylinder deactivation transition point .

Correction

Before reprogramming the ECM and TCM, compare the vehicle to a like vehicle. This may be a normal condition for an Active Fuel Management System equipped vehicle and no repairs should be attempted. The vehicle you are evaluating may be a little harsh in AFM transition. A calibration update was released for the ECM and TCM to soften the feel of the AFM transition.

SPS Information

• ECM -- New calibration to address customer concern of bump during active fuel management transitions. Must also program TCM with latest calibrations.

• TCM -- New operating system and calibrations to improve engine performance and shift quality. You must also program the ECM with latest calibrations.

Reprogram the ECM and TCM with the latest calibrations if the above concern is encountered. Updated ECM and TCM calibrations are now available to address this concern. These calibrations, or any that follow, are designed to address this concern. Refer to Service Programming System (SPS) using the appropriate Service Information (SI) procedures. The new ECM and TCM calibrations will be available to dealerships as part of TIS2000 incremental satellite update version 4.5, for 2007 (available on 04/23/07), and on TIS DVD version 5.0/2007 or later, which will be mailed to dealers on 05/09/2007. If you cannot access the calibration, call the Techline Customer Support Center and it will be provided. As always, make sure your Tech 2® is updated with the latest software version.

2007VMAX · June 26, 2007

You guys are a basket of knowledge! Thanks I will let it break in a little more and then get it flashed if it is still doing it, thanks again. And I agree with these trucks do run a little rough before they are broken in?! Wonder why, my 07 classic 5.3 was smooth from day one.

HuntingEd · June 26, 2007

I might be headin to the dealer to get my ECM reprogramed!

I occasionally notice the shift, but what I really notice is the chuggle or surge when im stopped.

My truck sometimes will surge for a split second at a light, not move but i feel it. Considering my truck was built in feb, I'll be getting that april udate!

VMax2007 · June 26, 2007

I might be headin to the dealer to get my ECM reprogramed!

I occasionally notice the shift, but what I really notice is the chuggle or surge when im stopped.

My truck sometimes will surge for a split second at a light, not move but i feel it. Considering my truck was built in feb, I'll be getting that april udate!

I used to notice that slight surge occasionally at a stoplight too, but how could that be related to AFM? It is in V8 mode when stopped. My truck now has 3000 miles and I have not noticed that in quite awhile now.

HuntingEd · June 26, 2007

I was wondering the same thing, I thought maybe V4 kicks in/off after you stop compeletly. Like if your in V4 upto the stopping point.

Im at 3600 miles, so im not sure.

hotwheels57 · June 26, 2007

I have only 1,100 miles on my '07 Silverado crew cab LTZ, 2wd, 6.0L w/ 3.73 gears. I haven't noticed the symptom, but my truck seldom gets into V4 due to the grade changes in the mountains @ 5,200 ft.

VMax2007 · June 26, 2007

I was wondering the same thing, I thought maybe V4 kicks in/off after you stop compeletly. Like if your in V4 upto the stopping point.

Im at 3600 miles, so im not sure.

No, it switches back to V8 mode at about 15 MPH or about 1000 RPM when decelerating to a stop. According to the DIC.

Gozer · June 26, 2007

I've been feeling a surge also with my 6.0L / 4.10's. Sometimes it occurs when stopped, and I have to push brake pedal down harder to hold it. Other times it's when trying to accelerate. This throttle by wire stuff with computer in between stinks!

I think I'll be taking it in to be looked at, along with a high-pitched "whistle" I hear coming from the drivers side under the hood.

VMax2007 · June 26, 2007

I've been feeling a surge also with my 6.0L / 4.10's. Sometimes it occurs when stopped, and I have to push brake pedal down harder to hold it. Other times it's when trying to accelerate. This throttle by wire stuff with computer in between stinks!

I think I'll be taking it in to be looked at, along with a high-pitched "whistle" I hear coming from the drivers side under the hood.

Wow, yeah, I would bring it in too. My "surge" was very faint, almost like someone pushing on the back of the truck with their foot. And it only happened after coming to a stop. It never does it anymore.

I am not a huge fan of "drive by wire" either, I think I will be getting a tune to take care of some of that TM.