[Shadofax]

I have an F250 that was making an intermittent scraping noise that was terrible. Was it a front wheel bearing? A rear brake pad dragging? Noises transfer in a vehicle. My problem was finally found by raising the truck and running it at 60 mph until the sound appeared. What was it? The center bearing on the drive shaft.

When you disconnect the solenoid you are releasing the clutch. The differential gears still turn. The drive shaft doesn't.

In other words, I'm not sure what conclusions to make based upon your experiment.

Having said the above, others on this Forum have had rear diff problems. The AMG diff oil change interval is 10K miles and then every 20K miles after that. In other words, high maintenance making me wonder why.

I'm not sure about all this Wayne. Let's start with your last sentence, accurate. The rear diff I have never seen what upgrades there are vs. a GLA250 even though there is way more HP and Torque, always why I was wondering how any power upgrades would allow differential pieces to survive (if you actually tuned a 45 for more power).

So the question here is if the car was mint, have the dealer show that the rear diff was at least serviced once. When I bought my 2015 with 18k, at 20k I paid to have rear diff, and front diff/tranny fluid/filter replaced, forget about service A/B blah blah.

Now, about the driveshaft and your comments....if he disconnected a rear diff solenoid, I'm not sure the driveshaft is not turning, if say the car is encountering a situation where AWD gets engaged (it's normally FWD, especially if in eco C mode. He didn't disconnect any solenoid at the front tranny, so driveshaft engages and spins down to clutch, which is likely disengaged, so no AWD.

That's an expensive fix though, I'll be tuned in to how this turns out.