[PaulV]

Hello all. My son has a 2011 Hyundai Genesis Coupe 3.8 Track. He told me he thinks he has a 'clunking' noise when accelerating from a stop. I've driven it myself and noticed this as well under standard acceleration - not hammering it at all. At first I was thinking U joint and after crawling underneath, I see this car doesn't have traditional U joints so that was ruled out pretty quick. To be honest, to me it seems a little more high pitched than a 'clunk' that I'm used to hearing with rear end problems. He sent me a screenshot of a post he found about missing differential mounts and it appears his LH rear differential mount bolt is missing. The RH is of a different design with the bolt running through a bushing set up in the frame. Not really sure how the LH should look, but the hole running through the frame is much smaller. Definitely nothing there now and looks like it may have been gone for a while. Part of me wonders if it's more of a 'slap' than a 'clunk' and if it could have to do with the servicing of the differential. BTW, we changed both rear axles and wheel hub assy's about month ago.
This is all new territory for me. I'm 52 and more of an old school car mechanic on old cars. I appreciate any advice or direction to go forward from here.

 

[Red Raspberry]

The left rear never had anything from the factory. Some have put a bushing there in place. A good mod to do. How are the motor mounts? And the flex disc do go bad. Rear will go first.

 

[AKGC]

Check the CV joint boots for leaks/tears .

If damaged, then better off replacing the halfshaft instead of trying to rebuild it.
Cheapest/better thing to do is get a used one off of ebay, without any tears/damage, replacing the boots and repacking the grease(Because might as well do it now instead later), then installing.
I say it's better, because normally OEM is better than remanufactured.

 

[PaulV]

Good to know about the left rear mount. I was thinking that because it looked like nothing had ever been in there. Both of the half shafts/CV joints are new and replaced about month ago. Haven't checked motor mounts but will. Are the flex discs what couples the ends of the drive shaft? I didn't notice any play in them, but then again conditions are different with weight on wheels and a load placed on them. Might take them apart do a more thorough inspection. Thanks for any/all the info.

 

[0101charlim]

Cheapest/better thing to do is get a used one off of ebay, without any tears/damage, replacing the boots and repacking the grease(Because might as well do it now instead later), then installing

Oooh, good alternative to driveshaft mechanic shops. Fingers crossed ebay sells good quality parts.

 

[expired]

my first gen coupe (2010 track) developed a rear "clunk" that seemed to make noise with inertia (for example, moving from a stop, braking, etc). Luckily it was still under warranty and the dealer had to replace my rear differential which cost them several thousand dollars.