Clunk heard when letting on/off gas?

[lasvegash2]

mine does the same thing....

[TGCOFTN]

My 2008 does the same thing.............my 2007 dont make the noise.

I know the noise your talking about, but I dont know how to describe it on a message board, LOL

[solarflare]

yeah, it's really hard to describe what it does...scared me yesterday though...I was in traffic and coming to a stop, and the front end went bang. Seems like a driveline issue. I did find that there are a lot of TSB's in regards to this problem, and that there are updates to correct it. The only problem is I don't know what the actual bulletins say, I just have the #'s. Here are a few:

99-04-20-002E JUN 08: Drivetrain - Driveline Clunk Noise Information
07338A JUN 08: Campaign - ECM Update for OBD Improvements
08080 MAR 08: Campaign - Reprogram the TCM
01-04-18-001F FEB 08: Drivetrain - 4WD/AWD Driveline Operating Characteristics
01-07-30-042E MAY 07 A/T - 2-3 Upshift or 3-2 Downshift Clunk Noise

[Stainless]

I occasional hear the same. My service guy said it was from running low octane gas. Are you guys running Premium?

[HummerJim]

My 2008 does it when it's cold or when I get off the highway and slow down to a stop after a long highway drive. I think it's the 6 speed transmission and I really don't notice it that much anymore.

[HumminNBoatin']

most likley the x-fer case.

[TGCOFTN]

I am like you HummerJim, I think its the 6 speed as well. Comparing it to the old 4 speed with the 6.0 liter is a lot of difference. Due to me having both, it was hard for me to get use too. At first I didn't really like it because of all the shifting, but I will say as time goes on, I am liking the 6 speed more and more. The past 5 days, I have tacked on over 2,000 miles on my 2008 H2 and got 19 miles per gallon with it.

-------------------------
To Stainless, I run Shell V-Power Premium in both of mine. Engine idles smoother, and dont downshift as much, plus you get better fuel economy.

2007 Hummer H2
2008 Hummer H2