Hello FitFreakers

I am at my wits end trying to find a "clunk" in the rear end of my Fit. It's a hollow sound clunk coming from under the floor of the cargo area, it can happen when going over uneven pavement, without hitting a bump. Hell, I had it make the clunk when turning hard to the right on solid pavement.

I've changed everything. Shocks were first, followed by the shock isolator mounts, then the trailing arm bushing. I've removed the spare tire and all that goes with it, made sure it wasn't the magic seats, I've zip tied anything lose inside (sun roof vent hoses, wire harnesses). I drove without a passenger side rear shock (havent done with drivers side removed) because it sounds like its coming from that side. I thought that was my fix but it just made it happen less frequently. I've had my buddy (ase master certified) sit in the back, he was sure it was coming from underneath. He also went over the vehicle and is stumped. There's more small things I've done and so far as I can tell, nothing has even made a dent in the volume of the clunk.

If anyone has even any ideas, I'm open to them. Thanks
2017 with 262k miles.

 

Check your muffler and all exhaust pipies.

 

I did a cat-back exhaust replacement in December because I (accidently) tore the old exhaust out. That was my first thought too, but when I grab the muffler tail pipe and shake that sucker as hard as I can, I can get it to clunk a little but it doesn't sound like what I get during my normal driving. I wedged a piece of wood between the muffler and the outer part of the spare tire well to keep it from moving and I still get the sound

This whole bit has been extremely baffling. I'd also like to add that I can't get the clunk to happen when rocking the car while stationary.

I'll be taking another close look at the exhaust, thanks for your help!

 

Here are a couple unlikely thoughts.

1) Any chance one of your rear springs is cracked or broken?
2) Have you serviced the rear brakes? With 262K miles, something could definitely be worn/broken in the drum brake mechanism.
3) Have you ever had interior panels or the door cards out (e.g., to repair a window or door lock)? Any chance something (e.g., a socket) got left behind? There is plenty of space inside the doors and rear hatch for something to rattle or clunk around. Similarly, in the right rear of the car (at least a GE8) behind the small pocket molded into the plastic interior panel there's a pretty large cavity. I'm pretty sure there are also openings/cavities at each back corner behind the plastic interior trim. Anything that got behind the trim could be rattling/clunking around in there as you drive, and depending on the object's shape/size/weight it might take a certain movement to cause the clunk.

 

The rear springs looked great when I had them out to do the trailing arm bushings, I completely redid the rear brakes two weeks ago, all hardware and drum + the wheel bearing. No change. I have had many interior panels off but I am almost certain it's nothing loose like that.

I was certain it was the hatch rattling for a while but I've locked that down as best I can, but that's the area it sounds like its coming from, though it's hard to tell since the rear is basically an echo chamber. I've tightened everything possible on and in the hatch.

I kind of think the clunk has been happening for years but has reached the point where my OCD needs to kill it.

Thank you for your thoughts!

 

Turns out there was an 8 inch horizontal crack in the rear axle beam. Problem solved, finally.

 

That's not good, but it's good you found it. Expensive?

 

Interesting.

I've started hearing a clunk somewhere on the left side of my GE. Yesterday, a buddy of mine (a mechanic) and I inspected the suspension front and rear, and we could not find anything that was wildly out of spec. I'll have to check my axle beam next time. Approx. 98k miles on the car.

 

Wow, I have the same clunk (2015) and I sure hope it's not the axle beam.
What did they do to fix it, did they weld it?

 

I just finished installing an axle from the junkyard to fix it, it's not recommended to weld it because the beam will still flex and the weld probably wouldn't hold.

It should be noted that I live in the Northeast where our roads are crap, and I have the habit of driving like it's a rally car + the very high mileage and almost daily use for the past decade, this problem probably isn't likely for your average user.

 

Maybe an undercarriage wash could have prevented your rear axle beam from rusting through.

 

Hmmm... while that is a low-hanging fruit option for why it happened, it's not really possible spray the underside all winter long, especially when you have to do 100+ miles a day in slush, 5 days a week all winter long. I've got a power washer and a garage and do my best to keep the underside clean, but that cant happen when its below 20 for a month at a time.

 

It is clearly a stress crack from fatigue load. Of course surface imperfections give a starting point to a crack, but axle beam can not be kept polished when the car is in use. I wish you many trouble-free miles with the new axle.

 

You're a good candidate for Fluid Film or similar. Basically, get the underbody as clean as possible in the Fall and then spray everything (except brake surfaces!) with Fluid Film, Wool Wax, or PB Surface Shield. Your heavy usage will likely mean it doesn't last forever, but all you really need is to get to Spring, when you can do a good deep-clean and then reapply the next Fall.

Even with a Fluid Film application, it's still a good idea to flush out the undercarriage when possible during the winter, but the coating should protect in between.

 

Although it's a bit late, I'm going to spray both Fits with Fluid Film.

 

This follow-up info is very helpful. Thanks.