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Discussion Starter #1
Has anyone else experienced a hollow rumbling noise coming from the rear of their truck? I thought it might have been wind noise form the crossbars so I removed them, no change. Made sure the spare tire is tight as well as all the skid plates and other bolt on items, including the Gibson exhaust.

The only thing I can think of is that the rear shocks might be causing it since they reused the OEM shocks on the 2" lift. I looked at them and they look almost fully extended with the lift installed. Can I replace the rear shocks with some ProComps or Ranchos and not screw up the ESP/BAS system? 4WP was going to do that but didn't want the liability issues with the ESP/BAS system.
 

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Discussion Starter #3
10500. Hard to tell, but it sounds centered. Only does it at high speed or when I go over something rough in the road. If I hit a manhole cover or similar then it sounds like it comes from one side.
 

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Unless its something like the exhaust rubbing against something I would be concerned about the rear differential. First thing I would do is make sure the differential is full of gear oil (or change the oil if its anywhere near time). If you do change the fluid or if someone else does it be sure and have it checked for any evidence of gear wear, ie small metal particles etc in the fluid. If there is no problem there then whatever the problem is it probably isnt serious. john
 

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Discussion Starter #5
Its getting close to its 12k service, so I'll have them look at it then. I think that a drain and fill of the rear diff is part of the service IIRC.
 

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I installed Rustys 2" kit which included new rear shocks. They said the stock shocks aren't long enough. I bet your problem is related to that.
 

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Discussion Starter #8
walkjon said:
I installed Rustys 2" kit which included new rear shocks. They said the stock shocks aren't long enough. I bet your problem is related to that.
Probably. Going to order the ES9000s for the rear install them to see if that helps. Didn't have this before the lift, so I think that's the culprit. 4WP wouldn't install them, very paranoid about getting sued if the vehicle is messed up or is in an accident due to their work.
 

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rwmorrisonjr said:
Probably. Going to order the ES9000s for the rear install them to see if that helps. Didn't have this before the lift, so I think that's the culprit. 4WP wouldn't install them, very paranoid about getting sued if the vehicle is messed up or is in an accident due to their work.
Who is 4WP? I want to make sure I never use them to work on my Jeep.
 

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Discussion Starter #10
4WP= 4 Wheel Parts. They're okay, good for bolt on stuff for newer vehicles, just very paranoid about lawsuits since they're based in Cali.
 

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Shocks are bolt on. 06-07 Commander is pretty new.
My Jeep dealer didn't have any problem putting my kit on. I did want them doing it though in case there was a future warranty problem of some sort. I can be paranoid about that kind of stuff.
 

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Discussion Starter #12
Just called 4WP to schedule the 10 day post lift inspection and asked them about the shocks. They said that when they tried the ProComps that the truck rode more stiffly and that it threw a CEL so that's why they didn't leave them on. They said they'd try a couple different shocks on the truck and see what happens when I drop the truck next Monday.
 

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rwmorrisonjr said:
Just called 4WP to schedule the 10 day post lift inspection and asked them about the shocks. They said that when they tried the ProComps that the truck rode more stiffly and that it threw a CEL so that's why they didn't leave them on. They said they'd try a couple different shocks on the truck and see what happens when I drop the truck next Monday.
Let me know how it turns out and what type of shocks they put on. Also, what's a CEL?
 

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Discussion Starter #14
CEL= Check Engine Light.

I'll post what happens next Monday after I get the truck back.
 

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rwmorrisonjr said:
Just called 4WP to schedule the 10 day post lift inspection and asked them about the shocks. They said that when they tried the ProComps that the truck rode more stiffly and that it threw a CEL so that's why they didn't leave them on. They said they'd try a couple different shocks on the truck and see what happens when I drop the truck next Monday.
Shocks throwing a check engine light? Thats a new one. I can see maybe throwing the ESP light, but not a check engine light.
 

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Discussion Starter #16
I think I had some other codes stored in there and the combo of the tires and lift finally caused them to throw the light. That subsequently threw the 4WP guys off and thus denied me some new shocks. Hopefully this can be cured on Monday and I'll be riding on some good shocks, not tapped out OEMs.
 

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Discussion Starter #17
Update: While I was driving home, I took the time to listen to where the noise is coming from. It sounds like its coming from the rear center, so that leads me to the rear diff or driveshaft. I'll have that looked at when I take the truck in for its 12k service next month.
 

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I wouldnt put it off if I were you. Unless its something rubbing it can only be one of two things IMHO in that area, the rear driveshaft ujoints or the differential. Either can get real serious real fast. You might crawl under and FEEL the differential right after driving it for awhile, if its really hot you got problems. john
 

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Discussion Starter #19
John said:
I wouldnt put it off if I were you. Unless its something rubbing it can only be one of two things IMHO in that area, the rear driveshaft ujoints or the differential. Either can get real serious real fast. You might crawl under and FEEL the differential right after driving it for awhile, if its really hot you got problems. john
That's the next step. I want to get the 4WP stuff done first so that everything they did is tight and the dealer can't say that the lift is what's causing the issues. Then if the noise returns its off to the dealer I go.
 

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Well, if its related to the ujoints it probably is caused by the lift. When you change the angle of the driveshaft it can cause problems with the ujoint. Thats not an expensive thing if you replace it before it breaks and your driveshaft goes bouncing all around from the roadway to your undercarraige. Also, I am not familiar with Commanders as all my mods relate to my TJ but they do today have special ujoints that can handle the more severe angle on the aftermarket. john
 
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