What could cause this noise/pulsing in the floor boards?!

robcarync

Sliders
Location
Raleigh, NC
OK..I have a 2004 Xterra, 4WD non S/C. This is driving me crazy.

When I drive, I get an intermittent/random pulsing/popping noise/vibration in the floor board. I feel it pretty noticeable where my left foot rests under the ebrake, and maybe a bit more faint on the right foot. It doesn't seem to be directly related to wheel speed, but it is hard to determine the root cause since it isn't consistent and doesn't seem to be influenced by wheel speed, transmission gear, engine RPM, etc. It really is bizarre to me. It is not a consistent pattern, but can almost sound like a faint sound of popcorn popping (maybe 4-5 clicks/pops/pulses and it stops for a bit). Speeding up had no impact...letting off the gas has no impact. It does NOT sound like a very mechanical/suspension CLUNK...it is more subtle pulsing in the floor board. The noise and pulse has no impact on the driving of the vehicle...it doesn't lose power, slow down, brake from ABS, or happen with suspension cycling.

Here is what I have done:

At first, I was thinking maybe a wheel bearing was "sticking" or not running smoothly at all times. I repacked them and it still made the noise. I then replaced both bearings and repacked with fresh grease/repacking tool, and it still makes the noise. I have inspected all brake components and cleaned all left over dirt from the pads/calipers and rotors. I made sure there were no rocks stuck in the tire treads. The tire spins very smooth with no bearing play.

I completely removed the 4WD hubs thinking maybe they were getting stuck and trying to engage the front Lokka or backspinning the drive shaft. Drove around the block, and the noise was still there. I got my wife to drive slowly and I verified the front CV axles were not spinning (granted it wasn't making a noise driving this slow).

I took the truck to a gravel road and cycled the transfer case and 4WD was working great.

All steering links are rock solid (grassroots center link, good tie rod ends, gusseted idler/pitman arms etc).

Literally, the ONLY clue I have is that it won't make any noise driving slowly (25 MPH or less in my neighborhood).

I think I have ruled out a bearing/hub issue. The transfer case and front driveshaft run right under the drivers seat, so maybe the transfer case is doing something funny, but it cycles through 2hi/4hi/N/4lo smoothly and without issue.

The driver's side catalytic converter and exhaust pipe is right under the pedal area. Maybe one engine bank is having a slight misfire causing a pulsing through the CAT? I have no CEL though...but did scan and find the P0327 knock sensor code. Maybe the 2nd cat is breaking down and causing a noise (that one wouldn't trigger a CEL, as it is down stream from the sensors).

I did get my brother to test drive it and I could barely hear it from the passenger seat, so I think it is more of a feeling than a noise...but he did confirm that I am not losing my mind and that there is something going over there.


ANY IDEAS HERE?
 

robcarync

Sliders
Location
Raleigh, NC
Not a bad idea...I didn't see anything wrong the fender liner...but it also got me thinking:

There is a heat shield above the catalytic converter which would be right where I am feeling it. The heat shield is bolted to the actual body of the vehicle. A year or so ago, it had worked loose and was squeaking a bit. It is possible the heat shield has loosened up and is flexing/springing back and tapping around. I am going to double check that now too.

Keep the ideas coming...I am confused on this one!
 

robcarync

Sliders
Location
Raleigh, NC
Prime...You may be an absolute genius!!!! I think it is a combination of a few things:

So...the regular fender liner looked tucked back and out of the way.

I went to take a look at my heat shield over the catalytic converter. It is literally right on the other side of where my left foot would be. It is on two studs sticking down from the body and has 2 nuts holding them on. I had some issues with that shield a year or so ago with non stop squeaking. I couldn't get a wrench in there due to access issues to tighten the loose shield, so I never got it tight (just smeared some grease between the shield and body at the time and that got rid of squeaking). Well, it looked even looser this time and was clunking a bit on the body and adjacent heat shields. A few scratched arms later and I somehow managed to get a wrench in there and tightened up the hardware.

The other thing that looks to be contributing: GAP GUARDS! After the body lift, the vertical wall/flap between the body and frame is ditched. I recently installed the gap guards from 4x4parts.com which is a heavy rubber mat about 1/4" thick. Well...you install it with plastic flips on the top side...but there is no good way to attach it to the frame (no holes in the mat...) so they are basically free hanging downwards. The front edge by the power steering gear also hangs down enough to get caught up on the pitman arm. Cycling the steering certain ways can push it out...pull it in...which can pull on other things (ABS sensor, brake line brackets, etc)...and the tire rubs on it. I am going to trim the mat so it doesn't hang so low, and drill a couple of holes in the frame to secure the mat on the bottom half.

I think what I was hearing/feeling was a combination of a very slight rattle of the heat shield, coupled with the gap guard getting tugged around and hitting on the tire. The gap guard on the tire fooled me into thinking it was rotational interference...AKA wheel bearings...where the clicks of the heat shield made me think a bearing was getting stuck and clunking intermittently. I test drove it after tightening down the heat shield, and I could barely hear and feel the noise or vibration (definitely improved...basically eliminated it but I am hypersensitive to the noise now!). That at least tells me the heat shield is influencing the noises. Without the clicking noise felt at my foot...the tire on the rubber mat was obvious when I heard it alone.

I am glad you put me on the wheel well liner train of thought. I had the bearings and locking hub apart 3 times cleaning and regreasing and triple checking everything. Nothing was out of the ordinary and I was about to drive myself insane.

I am going to drive some more this week to confirm it is gone after I trim the mats...but I do feel confident it is a superficial noise and no mechanical concern.

THANKS!!!!
 

Cruecible

Titan Swapped / SAS'd
Location
Albuquerque, NM
So what I gather from this is that Prime knows all. Except when he doesn't.

Glad you got it figured out! I still need to tackle some annoying maintenance things before it starts getting too cold
 

Prime

Shut up Baby, I know it!
Admin
Location
Denver Adjacent
I almost always know what I'm talking about.

You'd never feel wheel bearings in your feet. The rotational feedback would be absorbed by the rubber bushings of the lower control arms. You're more likely to feel bearings in the steering wheel. Kind of like an out of balance tire.

Feeling flapping at your feet is a short list of things it could be. There isnt much there.

As far as your gap guards, I would just get some fender washers and self tapping screws and secure the lower half to the frame and be done with it. I'd also see if you can get some epoxy or something on the studs for the heat shield so that they can't come loose again.
 

robcarync

Sliders
Location
Raleigh, NC
I almost always know what I'm talking about.

...even you left the door open for being wrong every once in a while!

:sure:

I tightened the heat shield hardware down as tight as I could and wedged a section of 5/8" fuel line between the shield and the floor boards. That should dampen any vibration from the shield.

I plan to do similar to what you mention with securing the bottom half to the frame. Super smooth cruisin' is my hope!
 

Cruecible

Titan Swapped / SAS'd
Location
Albuquerque, NM
Stranger things have happened.

4118bc185081d7b9ff5160dc6e5304cbaab081a7.jpg
 

robcarync

Sliders
Location
Raleigh, NC
Noise is completely gone.

Tightening the heat shield changed the noise from the clunky/clicky noise to the high pitched squeaky noise I used to have.

I am taking that thing out next chance I get.

Thanks all!
 
Top