Vibration from Rear of Car

[KayCee]

I have a mk4 gs450h i have not done much mileage due to the covid situation  I dont drive too fast maybe 70 + on motoway but have not had occasion to use motorway.

However in september of last i took my car in for service at Sheffield got the loaner car and awaited call that car was done  Gary at Sheffield rang said Robert you need new rear discaand pads shall i fit them So i said yes

Picked car up drove home no problem was busy so never reached 70 5 days later i got a letter saying i need to take my car in for Fuel pump recall i arranged another visit and took car in for pump change On driving home i did go 70+ and there was a vilolent shaking from rear of car i slowed and it went I did ring Gary who said we havent touched wheels but if you bring it back we will check as i didnt have the time i said i will ring later but due to lockdown I couldnt

On urban roads was no problem so forgot about it last night had to go to hull 70 + there it was again

as anyone any idea what it could be i did think maybe wheel weight fell off  putting wheel balance out but i thought that came in around 50mph

TIA

[paulrnx]

I’ve had wheel balance issues prevalent at 70-80 before so it is possibly this.

[Steven Lockey]

Could also be something that has become loose and is hitting it's resonance frequency at that speed. 

[The-Acre]

I don't know the GS brake set-up but on the LS if you take off a wheel the disc becomes loose and bits of flaky rust get trapped between the disc and the hub causing an imbalance.  It happened on mine causing a vibration until I cleaned the surfaces.

[KayCee]

Well stupid me

 

18 hours ago, Steven Lockey said:

Could also be something that has become loose and is hitting it's resonance frequency at that speed. 

Steven i checked in the boot and the cover over the Battery it as 5 pres stud type clips only one was engaged so it must have been the cover rattling at the resonance caused by the wheel balance

thanks all for your replies

Robert