Ok, got me an a technicality... But in 5th gear at 40mph, it feels like an overdrive gear.
No, it doesn't. moderate acceleration from 40 in 5th in no way feels like an overdrive.
lol. Ok. Let's forget I used the word "overdrive" to describe 5th gear. 5th gear around 40mph for me sits around or below 1600 rpm. A moderate acceleration would definitely feel like i was in the "wrong" gear.
That's definitely how transmissions work!
This is exactly how I would describe it, having been intimate with a variety of VW diesel engines in the past. Too low RPM and an attempt to accelerate basically stalled the engine and produced deep droning sound. The shape of the car's cabin adds to that.
You’re missing the point
If it is please explain to me why? I have read the manual but to be honest its vast and not very specific when it comes to details like this. Just says to vary the RPMs. Ive been driving like a madman and have bounced off the limiter more times than id like to admit.6th gear at 1500 rpm and only 200 miles on the clock ?
I understood that was a big no no for ‘running in’ ?
WD
The UK manual has this statement on the end of that section "Do not labor the engine" which to me seemed to fit what you were doing to get that noise in the first place.
Just be wary of continued use of the limiter (rumoured to contribute to oil pump gear failure) 
I couldn't accelerate from 40mph in 6th even if I wanted to lol. I downshift for 90% of my acceleration... It's more fun anyway. Just like shifting into 6th even if you don't really need to. We got manuals for a reason.There is no "seems like". 6th is a huge overdrive. You can use 6th gear at 40 mph if you want, so long as you use it correctly. It's not for acceleration unless you're going 60-65+, but even then you should probably downshift to 5th. Doing so sounds better anyway.
