Reply to "Gear oil level and change- New owner"

Steve, as a help, the stock fill and drain plugs are 17mm and a VW has the exact same size hex. So there are cheap VW drain sockets available, or you can shorten a metric allen with a sharp hacksaw. Be prepared with a drip tray: it's a sloppy job trying to get lube into the side of the cases with a flexible funnel or a lube pump.

The trick is, fill until lube starts drooling out. Stop for a few minutes, then continue to fill. It may take 3-4 tries before the cases stay filled to the bottom of the fill plug. There are many internal passages and cavities and 90-wt doesn't flow very fast. The books say a ZF holds 3-1/2 liters of 80W90, but you won't be able to put that much in unless it's a brand new bone dry assembly, as the same problem with cavities and passages happens when draining a ZF. You might only get 2-1/2 L. back in. Remember: too much lube only makes a big mess while too little wrecks ZFs.