Roaring sound coming from rear axle on 2006 Monaco Executive

[Doug Patton]

Am looking at 06 Monaco Executive on S Series chassis. 48,000 miles. Test drive revealed a roaring sound coming from rear axle. Unit has tag axle. Not sure dealer selling the coach has right mechanics to diagnose and properly repair the issue. Any advice as to cause of noise or known issues with 2006 Roadmaster"S" chassis would be appreciated.
Doug

[jacwjames]

I'd get a differential oil sample and see if there is any metal in it. I would also get someone to physically look at the ring and pinion and check tolerance and back lash.

I had a similar problem in my suburban differential, ended up having it rebuilt.

[Mr_D]

Does the sound change when you back off the throttle or when you add throttle? If so then the ring and pinion are needing a rebuild. If it changes with speed but not load then it's probably a carrier bearing.

[Stretch]

Just tell the dealer to install a new differential. Of course a roaring sound could be a bad wheel bearing.

[K7JV]

To me, a truly roaring sound from the area of the rear axle could easily be the engine cooling fan running on high speed. Our '06 Dynasty does that from time to time, usually very shortly after start-up. So far, it always calms down after a few minutes, although it may ramp up and back down a few times until it finally does settle down. It is incredibly loud if you are anywhere near it. Repair costs can, I understand, be a bit high, and since it hasn't gotten any worse in the past 8 or 9 years that it has been doing it, I've not worried about it.

[DtBt]

In addition to those mentioned above:
Ride height off can cause roar due to improper drive shaft angle.
U joints or drive shaft spline play should be checked as well.

[Twomed]

Re-man'd differential at Kenworth about $2,800 installed. Get it checked out for sure.