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  #1  
Old 04-25-2015, 02:28 PM
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low pitch "moaning" noise from rear of jeep

okay, i researched the threads and don't see anything quite like this noise coming from my jeep. probably 1 to 1.5 months ago I had both rear axle seals replaced on my 2001 JGC Limited because one was leaking pretty good and the other was just starting to. So I'm fairly confident that this noise is not coming from any wheel seals or bearings and the mechanic said my fluid looked good....not metal when he replaced it and he also said he put the additive in. But now, 2 weeks ago, my jeep has started making this strange noise when making mid to tight left and right turns and it comes out of it when going straight. a couple of times I also noticed a bit of a "studder" getting going after the noise, but that doesn't happen much. Now, if anyone has ever had a cv joint go bad ( which I did a year ago), this is kind of the same noise as that...it's almost like a tire rubbing, rubber kind of noise. not a metal grinding noise. the mechanic isn't sure what it could be but doesn't think its from the rear differential or the bearings. he thinks "maybe" could have something to do with the brakes(which I also had new brake pads put on the rear when he did the axle seals). he wants to take off the pads and drive it to see if the noise is still there.
So............any ideas what this noise could be? could it be warped rotors and it's only showing now because of the new pads? the differential wouldn't make this kind of low tone moaning noise would it?

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  #2  
Old 04-25-2015, 03:17 PM
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Re: low pitch "moaning" noise from rear of jeep

Is your jeep Quadra Drive? You mentioned the mechanic putting an additive in. For Quadra Drive some limited slip additive or friction modifier is needed to prevent the differential lock to lock completely. Adding no additive or not enough, could cause the differential lock to lock up completely when making a turn and cause one of the two rear tires to skip.
Also have a look at the T-case fluid or change it if not done recently.
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Old 04-25-2015, 10:03 PM
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Re: low pitch "moaning" noise from rear of jeep

Yes, it quadra drive. And ya, he said he put the additive in. I'll research the transfer case on how to check that or change it...unless you have a link handy for that info. I kinda think he doesn't really understand how jeeps work because I did mention to him that I thought it had something to do with the drive system because when you turn it transfers power from one side to other when turning because of pressure or what ever. He didn't seem to think that was likely. He also didn't know when he did my axle seals that other parts were needed besides just the seals....like the bearing and retainer. so my quote for that went from $250 to almost $400+ while he had it. :-(.
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Old 04-26-2015, 12:35 AM
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Re: low pitch "moaning" noise from rear of jeep

The Quadra Drive system on the WJ is a complete mechanical/hydraulical system. Each differential has a so called Vari-lok , which consists out of a pump unit and a clutch. Speed difference between two wheels on the same axle, will drive the pump and the clutch will be activated. The bigger the speed difference, the larger the output of the pump and the bigger the holding power on the clutch. When making a turn, the inner wheel makes a smaller circle then the outer wheel, so traveling less then the outer wheel. This speed difference will activate the clutch and make the axle one unit, with one speed. Ofcourse one speed for the two wheels can not work, since one wheel is traveling more then the other. One of the wheels will start skipping the ground and make strange noises because of this.
The limited slip additive will prevent a full lock of the differential, so allowing for the speed difference during a turn. I presume that not enough additive is mixed in the fluid.
A more or less same thing happens in the T-case, however there is no limited slip additive used. Normally most of the power is send to the rear wheels and a bit to the front. If a rear wheel starts spinning, the speed difference between the front and rear prop shaft will drive the pump and the (here called) progressive coupler will start sending more power to the front wheels. Old fluid in the T-case can cause same strange noises in the drive train. The fluid in the Quadra Drive NV-247 T-case is a special mopar fluid, which in fact is Mobil 424. The T-case has two plugs in its rear casing, the fill and drain plug. The fluid level should be at the lower side of the fill opening with the jeep level. Do not drain the T-case before removing the fill plug. It already happened to some that they did drain it first, to find out that the fill plug was rotten in place and they got stuck with an empty T-case.
Due to this system works on speed differences between wheels and axles, its important to use the same size of tires front and rear, left and right. Also wheels should be swapped front to rear regulary, to prevent more wear to the (more) driven rear wheels and premature wear of the progressive coupler in the T-case.
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Old 04-27-2015, 05:32 PM
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Re: low pitch "moaning" noise from rear of jeep

I crawled under it today and took a peek. the skid plate covers it, but I could still see that there is a mess under there. I don't know what all the parts are called but there's a part that's sort of cone shaped...but not to a point....idk, it's at the rear of the tc i guess. it's pretty oily/greasy looking all around there. The plugs you mention, would they use like a hex wrench to remove? I see a couple if that's what they are. Maybe this weekend while the weather is nice I'll just change it. You said Mobil 424....is it called Transfer Case fluid? Is it thick like the differential fluid and I'll need a pump to fill it?
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Old 04-27-2015, 09:42 PM
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Re: low pitch "moaning" noise from rear of jeep

The mopar specification for the NV247 T-case fluid is P/N 05016767, from which you will need 1.6L (3.4 pts). You can buy it at the stealer. For me the stealer is very expensive and i bought a gallon of Mobil 424, which is exactly the same as the mopar stuff, only without the big $$ (for me). I change the fluid now every year, otherwise i will never use the whole gallon.
Attached a page from the manual with the fill plug (upper) and drain plug (lower), which indeed need an allan wrench to get them out. Donīt remember the size of the allan wrench, but if you want, i can measure it for you. You will indeed need some type of pump to get the fluid into the T-case. I use a small squeeze type of pump and it takes quite some squeezing to get the fluid level at the lower side of the fill opening.
The rear T-case seal tends to leak over time. This is partly caused by the axial movement of the propeller shaft in and out of the T-case, when the rear suspension moves up and down. Also a clogged T-case breather tube can cause the fluid to come out due to thermal expansion of the fluid and increasing pressure inside the T-case. The breather hose goes from the upper front side of the T-case housing towards the engine bay and when iīm not wrong will it end into the breather cap somewhere in between the left cylinder head (as seen from drivers seat) and the fire wall. There is an other, same type of cap, mounted to the left shock absorber upper mounting stud, but that one is for the front differential breather.
Attached Files
File Type: pdf NV247.pdf (105.7 KB, 3 views)
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Old 05-10-2015, 10:56 AM
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Re: low pitch "moaning" noise from rear of jeep

how much limited slip additive does the rear differential call for? a local tranny guy suggested that I drain/siphon enough of the fluid out of the differential to make room for the modifier and just add the modifier.
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Old 05-10-2015, 05:41 PM
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Re: low pitch "moaning" noise from rear of jeep

It should be 4 ounces of limited slip additive.
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