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paddler1954 · 03-19-2017, 03:20 PM

We purchased our 2008 Expedition used in 2013. Ever since we have owned it there has been a whine coming from the rear of the coach as we boogie down the road. We always assumed it was a normal sound for a diesel pusher. Well, this week I went on a test drive of a new Allegro Bus my buddy is thinking about buying. Guess what, near total silence while cruising down the road.

This weekend I was planning on doing an engine and generator oil, oil filter & air filter change so..... I checked the differential fluid level, finger didn't touch any gear lube. :( So I drained the pumpkin, lube came out black and the magnetic drain plug looked like a 90's punk rocker with the spikey hair, not good.

Taking the coach to Freightliner tomorrow to get a quote on replacing the differential. The "over the phone" ball park estimate is $5000 if all goes well. We have an extended warranty but I'm sure they're going to ask for differential service records before they will pay any portion of the repair.

Painful lessons learned, 1) don't buy diesel pusher with whinny rear end, 2) drain and replace differential gear lube when I do my annual oil changes.

paddler1954 · 03-22-2017, 08:04 PM

Just a quick update. Final cost was $3930. So from now on, when I change the oil, I'll also be changing the differential fluid.

88keys · 03-23-2017, 08:28 AM

We've got a similar issue, but, our "whine" and "drone" is on an '08 Sprinter 3500 chassis.

When talking with some different differential experts, when they found out it was a "Florida RV" possibly sitting for quite a while, bells went off and corresponding sounds emanated from the phone.....as in, "ahhhh !"

Turns out, there were two issues with Sprinters :
#1) When Mercedes owned Dodge, as it was told to me, they imported the Sprinters un assembled, assembled them here, and they could possibly sit around for a while before being shipped on the docks.

#2) If it's an RV in a humid climate, the differential sits "half in -half out" of the precious bath tub that is the differential, with oil/fluid that protects it only covering half of the metal. The other half corrodes causing the characteristic "whine-pause-whine-pause...etc.." rotational noise.

The drone ? no idea. But, it occurs exactly at 55 mph which on rural Ontario highways is a perfect speed. Arghh !!!

The other nasty thing that I was told is that you can replace the whole thing and STILL have the exact same recurring problem. It turns out that differentials are made differently today than they used to be. The expert explained it but I can't remember the difference. There used to be a mitigating design which is no longer used....maybe much in the same way that transmissions these days are sealed !!! imho, this is ridiculous.