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Unread 06-06-2014, 12:20 PM   #1
Tombo_ontario
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2002 KJ Liberty 
 
Join Date: May 2014
Location: Windsor, Ontario
Posts: 29
Exhaust(?) drone only when driving not parked

I have had this issue for a little while, ever since installing an aftermarket muffler. Now I know, obviously, that the muffler is louder than stock, but not by much...and it gives more growl. However, I've noticed that at right around 1500rpm there is a nasty drone while driving around. This is especially irritating as it tends to be right at city cruising speed. This is not the case though if I rev up through the rpms while stationary...

So obviously it is being caused when the jeep is under load or perhaps there is something else that is resonating only while moving though?? The muffler itself gives a nice note while idle...definitely not loud at all...and when I rev up while stationary (parked), that too is a pleasant sound...not too loud at all...

Anybody run into this problem? Any suggestions? My next step may be to just try and tighten every nut and bolt I find on the underside...who knows lol

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Unread 06-06-2014, 07:29 PM   #2
tjkj2002
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2002 KJ Liberty 
 
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Revving in park will not have the same volume out the tail pipe since the engine is under almost no load or airflow(of passing air as your driving) as actually driving.

Gotta live with it or find a more stock replacement type.
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Unread 06-07-2014, 04:28 AM   #3
kirksjeep
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1992 YJ Wrangler 
 
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Location: CT
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Switch to a Dynomax. Affordable, and no drone.
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1992 YJ Sahara- 4.5" RE XD, 1" BL, 1" MML, 35" BFG MT, 8.8 w/Aussie, D30 w/Ten Factory shafts/ Aussie, 4:10 gears, Soild Diff Covers, SYE, CV Drive shaft, OBA, Flowmaster Super 44,, Custom head pipe, Super Chip, Boared out TB, Rock It Intake , Goferit Tie Rod Flip, 99+ intake manifold/Steering pump, custom front/rear bumpers,Hand Throttle, Hurst Shifter, Smitty Built sliders , 6" TJ flairs, Kilby belly up skid, Quadratech 9K winch, ZJ PS cooler. 01 XJ Sport-2" lift, 31x10.50 MT/ 02 Liberty 2" Lift
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Unread 06-07-2014, 06:29 AM   #4
Tombo_ontario
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2002 KJ Liberty 
 
Join Date: May 2014
Location: Windsor, Ontario
Posts: 29
Thanks guys...ya it just hit me that it's chambered and I've read bad things about them droning like hell. I'll see if i can pick up a dynomax or maybe even a magnaflow perforated core on the cheap side.
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Unread 06-07-2014, 05:10 PM   #5
02blue
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Location: Frederick, MD
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Just put a Dynomax High flow on my 4.0L Ranger and it sounds real nice. Ultra flo Welded.
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Unread 06-07-2014, 07:48 PM   #6
Tombo_ontario
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2002 KJ Liberty 
 
Join Date: May 2014
Location: Windsor, Ontario
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Anyone have a specific dynomax or magnaflow part number for the 3.7 liberty? Just wondering if I can get away with a shorter muffler than stock or if it's best to get same size...
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Unread 06-07-2014, 10:04 PM   #7
tommudd
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2004 KJ Liberty 
 
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Can't remember the number I have, its about half the length of a stock one, just found one with 2.5 in and out and offset/center
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Unread 06-08-2014, 12:00 AM   #8
kirksjeep
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1992 YJ Wrangler 
 
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I bought the Dynomax muffler and tail pipe at the same time from Jegs. They used to sell it as a kit, but now you have to buy both pieces separate. The only other piece you would need is the muffler clamp for between the muffler and cat.
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1992 YJ Sahara- 4.5" RE XD, 1" BL, 1" MML, 35" BFG MT, 8.8 w/Aussie, D30 w/Ten Factory shafts/ Aussie, 4:10 gears, Soild Diff Covers, SYE, CV Drive shaft, OBA, Flowmaster Super 44,, Custom head pipe, Super Chip, Boared out TB, Rock It Intake , Goferit Tie Rod Flip, 99+ intake manifold/Steering pump, custom front/rear bumpers,Hand Throttle, Hurst Shifter, Smitty Built sliders , 6" TJ flairs, Kilby belly up skid, Quadratech 9K winch, ZJ PS cooler. 01 XJ Sport-2" lift, 31x10.50 MT/ 02 Liberty 2" Lift
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