afn passat

humming road speed related .hums straight line and turning left when turning right sound goes away ...
so put car on axle stands to spin right wheel vibration and humming
so replaced bearing
replaced inner and outer cv joint
still the same
when up in air on axle stands sound went away when drive shaft was off
so i am thinking diff

so got hold of output flange from gearbox and i can rock it left and right but with a click....

tried same test on another good passat and no clicking ,,

question is there some kind of preload which can be adjusted cos on other side of box there is a ring of bolts ,,which might give me acess anyone throw some light on here

The differential carrier is preloaded by shims under the carrier side bearings.

Just because you can move the flange in and out doesn't necessarily mean that the bearings have play. I have never seen a diff with a bad bearing change tone on side-to-side loading, just driveline load (on/off the accelerator).

The best way to diagnose would be with a set of these:

https://www.amazon.ca/STEELMAN-97202-Wireless-ChassisEAR-Diagnostic/dp/B00123J79O

not in and out but left and right lol ...yes side to side load ,, suppose i might try replacing other side wheel bearing poss inner and outer cv as well ,,,just to rule them out ,, and yes can see huge advantage of microphones ,,,thinking about that with remote one on vid camera ...

Make sure you slather any parts with glue before you throw them at the car.

They might stick this time.

*Sarcasm*

Diagnose properly before wasting money on parts. If the Wheel bearing is bad, it may have play, and might be noticible from a passenger seat more than the driver's seat - as above listening to the part directly, preferably when you are able to make the noise happen is the best diagnosis.