Clunking Noise By Drivers Feet Upon Startup Sounds Like Something Cycl

[mc1984ss]

I have a 2006 Sierra 1500 4wd. Most of the time ( but not all of the time) when I start the truck I get a fairly loud clunk by the drivers feet, I can even slightly feel it in the floor. This may sould odd but it seems to be a valve or solenoid or something cycleing but I am not sure. It does not seem like a broken motor mount or anything like that. It only happens right when the truck starts and is stationary but it does not do it all the time. Thanks in advance, its appreciated!

[levigarrett]

Yep, I get this too. clicks twice. No Idea, I have a 2009 silverado

[MikeNH]

Is it just the AC compressor coming on?

[levigarrett]

No not the compressor. You only feel it in the pedal. like someone is tap it lightly.

[ChevyTech77]

Dessicant bag thumping around in the a/c systems receiver/dryer. Seen it many times.