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Old 02-11-2013, 06:29 AM   #1
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Help with exhaust interference

Over the weekend I replaced my entire exhaust system, downpipe back. I bought a "direct fit" system by Bosal that included all 3 cats and a dynomax muffler with tailpipe. Everything went pretty smoothly once I had the correct swivel socket to remove the mini cats from the exhaust manifold.
On my test run after completing the installation, I heard/felt something hitting. Come to find out, the u-joint on the front driveshaft is occasionally hitting the downpipe. While the jeep is parked, it looks like I have about 1 1/2" of clearance between the two, and everything feels really tight. I tried using a pry bar to see if I could get more clearance, but to no success.
Any suggestions or ideas. Should the engine be moving that much to cause the occasional interference? It seems to happen more pronounced when I brake from 10+mph. Should I just take it to a local muffler shop??

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Old 02-11-2013, 09:02 AM   #2
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Does anyone know if installing an adjustable front track bar would help this issue? The PO installed a pro comp lift but DID NOT upgrade the front or rear track bars. I'm getting ready to replace the lift with a OME 2.5 kit, so this would be the perfect time to replace the front track bar if you guys think it's necessary.

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Old 02-11-2013, 11:10 AM   #3
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I deleted my first response because I think I had it backwards.

Lifting a TJ with the stock track bar would shift your axle towards the driver's side, thus creating more room inbetween the pipe and the drive shaft. Seems like centering the axle with an adjustable track bar would only make it worse.

Something is not right, and no, your engine should not be moving that much. Have you checked the condition of the motor mounts?
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Old 02-11-2013, 11:39 AM   #4
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When you hung all parts... Did you leave it all loose first? You may have tightened down the down pipe with a swing sag to the driver side which would account for the rub. The pipe under the pan should be pretty level with the frame. Sagging down on passenger side would be evident looking under from front.
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~Todd~ 2004 X 4.0 5 speed---SOLD
4" Lift, 4.56's, 33" Duratracs on M/T Classics
RR SYE, Tatton CV, MML, BL, TT, Dynomax Exhaust
Hella Lighting: Driving, Fogs and H4 E-Codes
NOPE! ... and NEVER will be...
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Old 02-11-2013, 11:43 AM   #5
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I was thinking the same thing about the track bar but wasn't 100% positive.

What's the best/easiest way to check out the condition of the motor mounts? The original down pipe assembly I removed appears to have had interference issues at sometime in the past as well because its dented-in in almost the exact same spot that the new one is hitting.
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Old 02-11-2013, 12:10 PM   #6
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Quote:
Originally Posted by TnDz TJ
When you hung all parts... Did you leave it all loose first? You may have tightened down the down pipe with a swing sag to the driver side which would account for the rub. The pipe under the pan should be pretty level with the frame. Sagging down on passenger side would be evident looking under from front.
You probably just hit the nail on the head TnDzTJ. After I got the hanger in the transmission mount, I was more concerned trying to get the down pipe flanges connected fully and tight to the manifold than paying attention to make sure everything was level. This might also explain why I had such a hard time getting the flange on bank 1 to line up. Thanks for the heads up about checking for the pipe being level under the pan with the frame.
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Old 02-11-2013, 01:18 PM   #7
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Just loosen the flanges a bit and muffler clamps and see if you push up on the passenger side if you get it all to move up a bit. You should be able to get it level that way.

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~Todd~ 2004 X 4.0 5 speed---SOLD
4" Lift, 4.56's, 33" Duratracs on M/T Classics
RR SYE, Tatton CV, MML, BL, TT, Dynomax Exhaust
Hella Lighting: Driving, Fogs and H4 E-Codes
NOPE! ... and NEVER will be...
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