Kansas City Tdi & CoolAirVw Repair
01M Differential Fluid Change
To change the fluid in the differential either need to remove the rear diff cover to drain the fluid, then reinstall the diff cover with a new gasket, and fill it at the G22 location in the pic below. This would be the prefered method, but is fairly difficult and the gasket is silly expensive from Vw, like 20 bucks if I recall correctly, so most people would choose to suck the fluid out with a Pella or something similar.
In this pic you can see the speedo drive shaft and the gasket. Unfortunatly its difficult to get this cover off in the car due to blockage from the k memeber.
You suck the fluid out throught the G22 speed sensor as located in the pic below. You also refill through this as well.
The speedo drive shaft is used as a dipstick and Vw calls for less than a quart of refill in the diff to get the level to the bottom of the dipstick. Atra (auto trans rebuilders association) recommends overfilling it to the level of the "gear" itself". A happy medium would be to just dump in 1 quart.
Here's what happens if you put in a new trans and dont fill the diff. If your diff leaked and ran low similar destruction would happen.
The differential bearings spun out inside the case and destroyed the case. This unit was not rebuildable.