Clunk sound going in reverse in Model 3

[jpsgoneev]

This morning when getting ready to reverse out of my garage, the car did not respond to the slight press of the ‘gas’ pedal that usually gets it to s slow roll. So, I pressed a little harder on the pedal, and it started to budge but that was followed by a loud “clunk”. Not super loud, but it felt like something had given way.

After pulling all the way out of the garage, I found this thin metal rod on the garage floor under what would be the front right half of the car. I don’t remember seeing this in the garage floor just the day before the car was parked there.

One end is threaded (left side of 1st photo). The other end, which also appears to be bent, looks to have been sheared off. So I am guessing that this may have been the part that broke, causing the ‘clunking’ sound. The dia. is approx 1/16” - 3/32”.

Does anyone recognize this part from the underside of a Model 3? Thank you.

 

[brkaus]

The clunk is usually brake pads frozen/rusted to the rotor. Typically happens when the car is parked after driving in the rain.

 

[jpsgoneev]

The clunk is usually brake pads frozen/rusted to the rotor. Typically happens when the car is parked after driving in the rain.

Thank you, but I’m familiar with that type of clunking/resistance. This was different than that. This required much more force, and then the much louder clunk as if something had broken/snapped ... back to the rod in the photo above.

 

[AlanSubie4Life]

Were you using autopilot yesterday? Did you run over a bicycle? It is hard to determine scale from the picture with no ruler, but at 1/16" diameter that aligns with bicycle spoke diameter.

It looks like a bicycle spoke to me. I suppose it was possible that it somehow got wedged up there and the act of reversing caused it to "catch", while moving forward (yesterday) did not ("ratchet" behavior). I would at least look under your vehicle to see if you have anything under there though I'd suspect you would have noticed if something substantial was caught there. Like a bicycle wheel! More likely that a loose spoke from road debris somehow got caught up in something in the undercarriage, but really can't imagine how it would result in significant resistance unless it had to be stretched to free the wheel (bicycle spokes are very strong against elongation...but that's "bicycle strong," not "car strong"). When cutting spokes on a wheel (the nipple was seized and rounded so no way to loosen gracefully) I've launched them at extremely high velocity across my garage in the past. Enough potential energy stored in the stretch to launch the (light) spoke 20 feet across the garage and bounce vigorously off the opposite wall. I'm lucky it didn't hit any of my cars. I was wearing eye protection of course.

Seems unlikely that a bicycle spoke would have anything to do with the resistance though. There are places you could stick a spoke (like through the Model 3 wheel "spokes" so it was wedged against the caliper?) and get this result I guess but it seems improbable in context. I suspect the brakes too, but you say it wasn't that, so I have no idea.

 

[mrElbe]

The thread is too long for a bicycle spoke. But still could have been some debris picked up on the road.

 

[AlanSubie4Life]

The thread is too long for a bicycle spoke. But still could have been some debris picked up on the road.

It's really not too long. The only question is scale.

Here is an actual real-life bicycle spoke! Thread length can vary, too (you want to make sure you have enough otherwise you may not be able to achieve desired tension, though the total length obviously plays into that too...my point is that for a correct length if you don't have enough thread you might not get the tension). This one is actually really close for my bike. 21 thread turns vs. the OP's 23.

Obviously it could be a spoke-like object for some other purpose as well. Reasonably sure it is not part of the Model 3, if we have the scale correct.

 

[jpsgoneev]

Thanks for your input. I’ve added a few more photos for scale. Length of (broken) rod is 9-in. Threaded portion is approx. 3/8-in. The bicycle spoke theory is an interesting one and I’ll check the bikes in our garage for missing a missing spoke (?). Or, as mentioned, possibly picked up as road debris (or placed there after parked?).

I just wanted to make sure that this wasn’t a part from the underside of the M3, or perhaps used to hold panels/other parts in place (in tension).

 

[AlanSubie4Life]

Thanks for your input. I’ve added a few more photos for scale. Length of (broken) rod is 9-in. Threaded portion is approx. 3/8-in. The bicycle spoke theory is an interesting one and I’ll check the bikes in our garage for missing a missing spoke (?). Or, as mentioned, possibly picked up as road debris (or placed there after parked?).

I just wanted to make sure that this wasn’t a part from the underside of the M3, or perhaps used to hold panels/other parts in place (in tension).
View attachment 382979 View attachment 382980

Pretty much looks like a spoke (they can vary in diameter depending on the quality and purpose). Obviously other identical threaded rods for other purposes exist.

Always worth looking under the car to make sure you have all your aero cover bolts, anyway. I'd do a visual inspection with a flashlight if I were you. But yeah, I doubt this is part of the Model 3.