Replacing crown and pinion for audi a4 2000 multitronic

this indicates failing bearings on the pinion shaft allowing the mesh of the pinion and crown wheel to alter
check for oil in the diff and metal on the plug magnet
if there is a problem you can get good low mileage replacement centres from the wreckers cheaper than repairing yours

if the noise is occurring on acceleration it will be the rear pinion bearing
if it is on deceleration it will be the front pinion bearing
if it comes and goes s you drive normally it is the incorrect mesh between the crown wheel and pinion and indicates worn carrier side bearings allowing the mesh of the crown wheel and pinion to vary
check for correct oil in the diff and check magnet on drain plug for metal bits

Adjustment to crown wheel and pinion has to be done after bearing replacement on the pinion and carrier. It is a method that unless you have done a lot of diff repairs will amount to a trial and error procedure to get it right. Fortunately any work shop manual that you can borrow will have the way to set up the diff and there will be photos and directions on which to move to get the setting right. It is important to get the reading right as correct gear mesh will ensure a long lasting quite diff operation.

a noise from a diff are , normally a high frequency harmonic sound while driving is from diff pinion bearings
if you decelerate and you get a noise normally as a low grumble ( low drumm noise )to a frequency noise is again the diff pinion bearings
you can distinguish the noise from power on to deceleration
the noise can be most noticeable with a slight load ( 2 people travelling at a steady speed say 60- 80 klm/hr) as a steady but harmonic pitch variation
the noise varies as the load is transferred from the bearing immediately behind the pinion gear to the bearing immediately behind the drive flange or in your case driven gear from the gear box
it is caused by a slight movement of the pinion which varies the correct mesh with the crown wheel , resulting in the whining sound
sorry but noise sounds are very hard to describe

Low transmission fluid. Manual gearboxes normally use gear oil, automatics use transmisison fluid. Sill could be a bearing, just not a wheel bearing. Just curious, how can you tell its not a wheel bearing?

Whining sounds come from diffs that have a problem in the mesh between the crown wheel and pinion If yours is not front wheel drive then the noise may be from over tightened wheel bearings or failed bearings or the abs sender touching the exciter

Wow this a touchy. There are several options to look into. Don't be mistaken with always the most obvious. Sometimes the problems occur right in front of our eyes and we still cant find it. A option i'm thinking is, and i'm not over ruling that what you mentioned, but is to jack up the vehicle with all wheels in the air. Use safety when doing this. Fire up and put her into gear try going through all the gears. Rev only to about 2000 rpm. Get out and try to listen all around the vehicle. Listen to wheel bearings, actually after a drive you place your hand on the wheel hub and feel for high temperature. Wheel bearings get hot if they are on the way out. Listen for grinding near the diff sections, Listen in the engine compartment. Use a long steel rod or something place the one end on the gearbox near the engine and place your ear on the other side. My guess is your crown wheel and pinion on the diff is on the way out. Yet difficult to establish, but when you go through all the gears maybe even look at gearbox syncs. A good way to establish if the pinion of diffs are the culprit is to get under the vehicle when on the ground, engine switched off, and in neutral handbrake down, is to feel propshaft play on the pinion. It shouldnt rotate more than 2mm either way.

That is very likely a wheel bearing staring to go out to lunch.

Wierd Wheel Noises:

New bearing is actually good? Take wheel off of the ground, vehicle in neutral and rotate the wheel by hand and see that there are no problems with the bearing, CV Axle, or the brakes. And put some pressure on the bearing as much as you can to make sure it is not binding itself.

More than one bearing has been damaged during installation. I now own a 10 ton press and keep it in my basement for the next time I have to replace my bearings. Thank goodness I always buy in pairs.

Here's to hoping you just identified your problem.

If not, then: Have someone turn the wheel in both directions while watching the CV Axle at both ends, to make sure it isn't the problem.

One more issue: Swap your tires front to rear, and rear to front, and drive to see if your noise changed locations, indicating a tire or wheel problem.

If everything you just checked is working properly, then you know what's next.

Good luck !

SELL SELL SELL!!! I have owned various audi's over my lifetime and have always loved the quality and drive that they offer but when i bought my first auto which was multitronic i had nothing but big problems! costly problems which ended in a replacement gearbox and surfing the internet has brought to my attention that i aint the only one!