L405 rear end vibration like an out of balance wheel...but it's not

[Daveykid]

Hi guys, I have an issue that is driving me nuts.

2021 L405 SV Autobiography Dynamic Holyoke edition here. Has anyone had any issues with what feels like a rear wheel out of balance? Here's what we know so far and what we've done:

Starts around 73mph and remains until 85ish. It's a pretty short range and smooth otherwise.
Stock wheels/tires.
14K miles on the truck.
Never an accident.
Never so mush as a curb rash.
Had the wheels balanced a few times now in the hope of thinking it might be just that.
Had the tires spun on the wheels to help achieve a “zero” balance.
Have been to three different places including the dealership for the wheels.
Tried a second set of OEM wheels off another one and it's still there.
Swapped rears to the front and it’s still in the rear so I know it’s not the wheel/tire combo.
Happens no matter the outside temps and tire pressures are per factory spec.
Perfect alignment. No unusual wear on the tires.
The dealer had another L405 Autobiography on the lot with the same size wheels and options and it too vibrated around the same speeds. I'm going to test drive that one Saturday to confirm.

I think it's safe to assume it's not a balance issue at this point. So...

They recorded the vibration on a Picoscope and sent the results for analysis to JLR New Jersey. JLR just told me the vehicle is “within spec”. Yes it was elevated up the chain to their engineers (opened up an Engineering Case) and it is as high as I can go in the US. The technical advisors in New Jersey are stumped.

Thoughts? Known issues? Wheel hub? Driveshaft? Rear axle? Anything else I can't think of that I should chase? I’m at wits end on this one. Thanks!!!

 

[alldazed]

Is it fitted with the harmonic balance weights that hang from the rear corners up inside the rear bumper corners ? I have a 2011 RRS that will occasionally do a weird shake / sound at certain speeds but clears up. Does it every few months. If you google harmonic weights Range Rover you will see what I’m talking about. I think they are supposed to hang freely so feasibly dirt could interfere with that. I assume a dealer would consider this though at the level it has been elevated too.

 

[Daveykid]

Is it fitted with the harmonic balance weights that hang from the rear corners up inside the rear bumper corners ? I have a 2011 RRS that will occasionally do a weird shake / sound at certain speeds but clears up. Does it every few months. If you google harmonic weights Range Rover you will see what I’m talking about. I think they are supposed to hang freely so feasibly dirt could interfere with that. I assume a dealer would consider this though at the level it has been elevated too.

I have no idea what they've considered (or haven't for that matter) but it's worth a shot at this point. If I used the truck for mostly city or short suburban driving you would never know. Unfortunately it gets a decent amount of highway "trip" time and it's almost annoying as the dealer telling me it's "within spec". One of the most annoying and insulting things a dealer can tell you when they are clueless about their own product.

 

[Daveykid]

As a follow up from the engineers at JLR, they are aware of the problem that exists with the L405 body vibration at certain speeds but are unwilling to pursue it any further. It is operating within "spec". So there you have it folks. Great vehicle, just don't drive it between 73-85 without the fear of losing your fillings.