Chrysler Repair: Rear end noise: 06 300c AWD

Question
QUESTION: I have an intermittent noise from the rear end of my 06 300c (5.7L) AWD Chrysler 300.  The car has 112K on it and has just completed a 2000 mile trip. The noise is becoming more frequent and seems to be more prevalent when turning left.  The rear wheel hubs and bearings have been replaced, but this did not address the problem.  Also, when I turn the ignition off, the problem seems to disappear.  Any help would be appreciated.
Thanks.

ANSWER: Hi Tom,
Have you checked the level of lubricant in the rear axle. There is an access plug on the side of the differential which you can remove and insert your finger to sense if there is lubricant near the lower level of the opening. If you need to add get Mopar synthetic gear and axle lubricant 75W-140. The capacity is 1.4L if you would want to drain and refill the unit. Do it after warming up the vehicle by driving it some.
I checked my '06 manual which I have on CD and find there are sections of the manual that relate to the AWD system, but you need to know more about the specifics of the noise source.
If you mean that the noise disappeared while in motion but when you turn off the ignition then that may be due to the fact that you were 'coasting' with no motive power being applied to the rear axle. That can mean that your lubricant level is low. Noises that mainly occur during turns are usually related to the "side gears/pinions" which are called into play when you turn.
The AWD has the transfer case and rear differential units, each of which is described in detail in a separate section of the manual. I can copy some noise diagnostic pages for the rear differential. It  appears that the 198R is the rear differential unit used in your AWD vehicle.
There are several pages that describe how to differentiate the source of the noise. I can copy and send those to you as attachments to an email.
Let me know your email address but don't use the @ symbol, instead use "at" or the address will be erased.
Please read the PS (below) and respond to it.
Thanks,

Roland

---------- FOLLOW-UP ----------

QUESTION: Roland,
Thanks, it makes sense, but there has been no evidence of leaking at the differential.
My e-mail address is: thomhickey at aol.com.
Will check the fluid level and add as needed.  What about an additive to the fluid?
Tom

Answer
Hi Tom,
I'll copy the pages this morning and send them to you. I don't have an opinion about additive fluid for the differential except as a last resort before removal/repair.
Thanks for the rating and nomination. You can do both again if you would care to do so.
Roland