The driveshaft has splines in it to allow it to change length as the suspension cycles. If the axle bolt loosened up enough it might be possible for the driveshaft to try to compress to a size smaller than it is capable of, putting an excessive side-load on the cv joints, causing thumping. Keep in mind this is quite unlikely...

 

o ok now i see what you're saying... i just showed my friends dad whos car savy, says he's almost certain its the bearing. sucks. im going to try and tighten it a little and see if it makes any change. Does the car have to be off the ground to tighten that bolt and is it reveres threaded?

thanks

 

if you can shake the wheel its probably bad bushing's control arm upper and lower and tie rob inspect all of them a very small amount of ware can cause this symtom

 

That bolt is supposed to be tightened with the car on the ground. It's got the typical right-hand thread.

 

IIRC, it is supposed to be tightened with the suspension loaded, but not necessarily on the ground. Correct spec is tighten to torque spec unloaded, then load suspension (lower to ground if DIY) and tighten to specified additional turn specified.

...HOWEVER... if it is a used bolt, pull it out, loctite it, and tighten bolt while making a wish for it to stay. It is supposed to be replaced every time it comes out.

Stupid, and maybe obvious question, but what size wheels are you running? A8 upgrade with 16" wheels will cause rotors to hit stick-on wheel weights, creating a thumping sound. It's just another thing to check and eliminate.

 

I just read through my service manual, and it reads (and I quote):
I've been re-using the same bolt for quite some time now... I know, shame on me. But it's never loosened up on me; my biggest fear is it breaking. Though today it will be getting replaced with a brand new one

 

Interesting. Which service manual? Maybe I'm confusing it with a Jetta or something. Most axle/bearing bolts are stretch bolts, so they are torque to spec, then turn an additional 90 or 180 degrees loaded.

 

I am on 16" wheels, and I'll check if there are stick-on weights but it started making the sound before I upgraded the brakes. And there is no doubt the right front has more play than the other side. So that's an issue I still have to address. But the sound is only brought on under braking not any other time and I think if it was a rotor hitting stick-on weights it'd make the sound all the time. Doesn't make the sound when braking in reverse only when braking forward

 

Correct on all counts. My vote also goes to the wheel bearing with this info.

 

Lol nvrmnd.