Knocking while braking

[SilveradoCA]

I have an odd symptom; it started a little while ago, but is 10X worse today, which is the first day we've had weather below -20°C.

When I brake, there is a knocking noise, which seems to live right underneath and slightly to the right of the console/shifter area, but definitely not inside the cabin itself.

It sounds a lot like the sound a failing/failed CV joint would make while turning. This isn't present under any other condition but while braking.

I can't decide if this is an actual knock, or a flexing sort of sound, but it's present whether I brake gently or hard.

What should I look for under there?

 

[briteboy]

I'm sure it could be a multitude of issues, but I remember a post here several months ago that showed a stabilizing arm for the transfer case or a suspension member that was broken, and it was near the center of the car, under the console area. Looked like a stress fracture.

IF...it's something like that, I could see where the knocking would come from the flexing of the power train or suspension under braking.

Take a look at all your suspension parts, exhaust hangers (I think there is one near the tranny) and stabilizing supports. You might get lucky and find one that's busted, and would be a "simple" fix (if there is such a thing).

Good luck. Let us know what you find.

 

[LukerDooker]

Does it alternate with the knocking literally at the top of the center console at the arm rest door, and sometimes the knocking is further down, but still felt in the console?

 

[Bill #5 Explorer]

Cracked rotor?
Cracked brake pad?
Strut bearings?

 

[dudefish]

Are you hearing only one pop/crack sound per pedal application, or is it a repeating pop-pop-pop-pop? If a repeating pop-pop-pop, what is the sound frequency and does it relate to vehicle speed?

The first thing I thought of was cracked rotor, but the nature of the sound isn't clear. More info would help.

 

[SilveradoCA]

Forgive my possibly incorrect parts nomenclature... I'm a carpenter!

The lower suspension sub-frame has two brackets (one on each side) which connect it to a crossmember in the unibody, about under the footwell. Each bracket has a large bolt at the front which connects to - I believe - the front body mount? At the rear of each bracket are two bolts (1/2" hex head, with washers) which thread into the crossmember.

All four of those bolts - two on each side - were backed out almost exactly 3/8". The brackets are slotted where these bolts pass through. Tightening them back up has eliminated the problem completely.

Clearly when the weight of the vehicle shifted forward under braking, these loose mounting brackets were creaking against the crossmember, causing the noise.

I find it unlikely that all 4 would uniformly back out the same amount! Are these bolts loosened during a wheel alignment?

 

[dont slow down]

Interesting but very odd. I wouldn't see that as a coincidence and I have no idea whether or not it is used during the alignment process. I'm dealing with a "clunking" noise in my front end as well, it's currently at the dealer getting new lower control arms however I am going to check those bolts as well on mine.