Rattle from below floorboard above 15 MPH ('05 Rubicon with manual transmission)

dukegrad

dukegrad

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Joined
May 14, 2021
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20
Location
Fort Mill, SC
I might be grasping at straws, but hoping to get some help troubleshooting a new rattling noise from my 2005 Rubi 6MT... Here are the particulars.
  • Rattle sounds like it's coming from the center/front, between and below the front foot wells
  • Sounds kind of like a big washer rattling against something
  • Noise happens only above 15MPH and gets louder with speed. There are no noticeable pitch or frequency changes with speed (ex. it's not a tick-tick-tick you'd hear from a u-joint, bad brake, etc.). Noise get quieter as you slow down and goes away completely when back under 15MPH
  • The NSG370 tranny was rebuilt about 10K miles ago, and a new clutch and throwout installed at that time
  • Rear axle is a double cardan with proper pinion setup (no drivetrain vibes)
  • Except for the rattle, there is no noticeable difference when driving (no vibes, grinds, pulling to one side, etc)
  • No recent changes to anything, other than installing a new stereo (noise appeared a couple weeks after that, seems unrelated)
Here are things I've checked:
  • Engine RPM and gearbox don't have any effect (changing gears, no difference)
  • Transfer case doesn't have any effect (placed both tranny and transfer case in neutral and coasted down a big hill, noise appeared at ~15MPH as before). Also tried 4H and same noise
  • Clutch in/out same issue (so doesn't seem to be throwout bearing related)
  • No change to noise under normal or aggressive braking
  • No change to noise when using e-brake (thought a loose cable rattling against something could make that sound)
  • Checked u-joints on both drive shafts, no abnormal play or wear
  • Took a rubber mallet to skid plates and anything else that looked like it could be it. No dice
  • Checked exhaust and hangars. Nothing obvious there.
Any words of wisdom from the experts?

-Eric
 
Have you looked around inside for the noise? I have what I first assumed was a rattle coming from under the Jeep. It was intermittent, unlike yours sounds, but occurred almost every time I hit a decent size bump. I haven't verified it yet but I suspect it's a blend door or something similar in or under the dash. The fact that my HVAC blows weakly on the floor with the selector on dash seems to support this.
 
Mine rattle sounds about the same and have determined it is the heat shield above the exhaust mounted to the tub. All the bolts pulled through it and it’s loose.
 
Being it is speed induced I would guess something in transfer case or front driveline/drivetrain. Yokes on tcase didn’t come loose did they?
 
I had rattling once and couldn't figure out where it was coming from. By accident, I discovered the problem when I decided to clean out the torque boxes. The previous owner had removed the floor plugs, resulting in stuff on the floor falling into them. Here's a sample of what I found on just one side.

FWIW, I found almost $10 in various change there, along with an assortment of nuts, bolts, and miscellaneous other crap!

zUTwMyz.jpg
 
  • Wow
Reactions: Zorba and Chris
joelachr said:
Have you looked around inside for the noise? I have what I first assumed was a rattle coming from under the Jeep. It was intermittent, unlike yours sounds, but occurred almost every time I hit a decent size bump. I haven't verified it yet but I suspect it's a blend door or something similar in or under the dash. The fact that my HVAC blows weakly on the floor with the selector on dash seems to support this.
Click to expand...
I did. No carpet and no mats, not much to rattle in floorboard :)
 
Irun said:
I had rattling once and couldn't figure out where it was coming from. By accident, I discovered the problem when I decided to clean out the torque boxes. The previous owner had removed the floor plugs, resulting in stuff on the floor falling into them. Here's a sample of what I found on just one side.

FWIW, I found almost $10 in various change there, along with an assortment of nuts, bolts, and miscellaneous other crap!

View attachment 253275
Click to expand...
Woah! Haha! Mine has had the plugs pulled for years. Still to this day I find an old cigarette butt in the floor occasionally. (I don’t smoke cigarettes). Worth checking those torque boxes! Researching…
 
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Gollywomper said:
Being it is speed induced I would guess something in transfer case or front driveline/drivetrain. Yokes on tcase didn’t come loose did they?
Click to expand...
Drivetrain seems fine. T-case was my best guess previously too, but 4H and t-case in Neutral (coasted down a hill) both yield same noise. Any other thoughts on how to troubleshoot/isolate the t-case?

I also thought about disconnecting the front drive shaft for kicks to see if it went away. Sounds more back toward t-case direction than front shaft/axle though.
 
Honestly best way I've isolated these types of things is get you phone on a tripod under your jeep in a bunch of locations and jump up and down on the bumpers, rock it back and forth by the doors, in gear rock it back and forth. Its amazing what the camera will pick up. I do this at least once a year and always find a loose bolt or something getting ready to fail.

I'd guess it is your shifter linkage.
 
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