So I've been looking online and haven't really came to a conclusion, I browse here often and seems like there are a couple guys in here with a lot of knowledge.

When hitting small bumps, turning, or during the occasional shift, I get a clunk right under the floorboard in the drivers side.

From reading, there are a couple options.. it seems that the strut mounts were a problem, but people have also pointed towards the axles and even tranny mounts.

Just looking for a friendly discussion or perhaps some suggestions.

definitely check axles first, if a boot is torn youve probably already lost all the grease on there which would wear out the CV joint pretty damn quick.

telltale signs is if theres grease flung all over the components around the boot of course.

strut mounts wouldnt really do that on shifting, and it definitely wouldnt be under the floorboard, and you'd most likely feel it in the steering wheel.

transmission mounts are my second guess, after a bad CV join on your axle.

how many miles does your car have?

I already took a quick glance at the boots and they look okay, but I will double check those. As for axles should I just look for end play and/or freeplay?
Car only has ~114,000 KM on it

yeah pretty basic check too, you'll know if one side feels worse than the other for sure.

end links or the bushings for the sway bar, or bushing in the control arms cause this 9/10 times on cobalts.

http://www.carparts.com/details/Chevrolet/Cobalt/Mevotech/Sway_Bar_Link_Bushing/2007/LS/4_Cyl_2-dot-2L/MEMS50402.html

http://zzperformance.com/ecotec/suspension-brakes-handling/moog-front-sway-bar-end-link.html 11.8" for base model

9.86" for SS

as for if your worried about the control arms just buy new ones its more expensive to get all the bushings VS buying new control arms with all them in already

http://www.carparts.com/details/Chevrolet/Cobalt/Replacement/Control_Arm/2007/LS/4_Cyl_2-dot-2L/REPS281508.html
http://www.carparts.com/details/Chevrolet/Cobalt/Replacement/Control_Arm/2007/LS/4_Cyl_2-dot-2L/REPS281504.html

left and right side 35$ a pop for stock replacement with all bushings and ball joints already installed

This post was edited by night_throne on Jul 11 2015 04:07am

yeah but control arms wouldnt cause him to feel it in his floorboard...

im by no means saying it is the control arms in this case im just giving him all his options and at the mileage it wouldnt be a bad idea to do them anyhow

Thanks for the suggestions guys, really appreciate it. Hopefully tomorrow I will have time to look into it further!

Also, I forgot to mention I don't feel anything at the wheel, it's just a clunk in the floorboard.

I guess my plan of attack is to check play in the axles and then check out the strut mounts, as I'm going to assume that's the issue, but who knows

let us know how it feels