haraldpost

I bought 2 litres of 75W-90 oil with plans of doing preventive maintenance on my car: 96 Audi C4 FWD automatic transmission (CRD). But WHERE is the drain plug? Thought I was going blind, had my father have a look. It looked like there was a hole blinded off where there should have been a drain plug. We tapped it lightly with a hammer before we decided to leave it alone. After all we do have a manual pump, so plan B was to suck out the old fluid. I removed the exhaust to gain access to the fill plug. But it turned out there is no way in hell I am able to get a thin hose down to the bottom through there. We tried one hose after the other, with no luck at all. Do we really have to undo the center bolt on the hub and remove the drive axle and flange to be able to suck the fluid out??



I ended up just topping it off... cars done 200.000 kms (124.000 miles) and I can't find records of a diff oil change. I suppose it is "lifetime" like the ATF and the servo oil. Which is fine if you plan to scrap your Audi after 100.000 miles.

egp320i

You are not blind, no drain exist for the front "pumpkin". Mighty vac is popular.
Audi states lifetime but nothing lasts that long and changing it is a good idea.
If the oil is original you probably got a whiff that smells like a sewer, it's nasty.

Vacuum out as much as possible, top off till it dribbles by the threads and your all done.

Last I recall the fill hole was by the drive shaft and you did not have to remove the exhaust. It's been a long time or I could be thinking of another model.

Rusty Spokes

Could be the fill hole is the round thing with the allen socket fitting just left of the axle in the picture?

egp320i

Yeah, that's about what it looks like. I recall my 90 is on the left but the A6 certainly could be on the right.
Come to think about it I don't recall ever changing this fluid on mine, I think the shop did it long ago.

haraldpost

You are right, with the right tools it is not necessary to remove the exhaust to access the fill plug. The plug is on the passenger side.

I tried a vacuum brake bleeder tool to suck the fluid out, but had no luck as it is not possible to insert the hose into the "pumpkin". It was sucking air. Maybe it is possible with a strong vacuum pump and a good seal.

I had the car raised and removed the front wheels. I put bolts in the brake rotors (never forget..) and fastened one with pliers so it couldn't turn past the caliper. I started the car and let it idle in drive. With the fill plug out the differential gushed out oil. I filled with fresh oil and repeated a few times. For the first drain I jacked the car to the side to get most oil out. I used 2 litres 75W-90 synthetic.

egp320i

Unorthodox but if it worked. As noted mity vac has been used often with good results.
If you were grabbing air it was either low or not inserted to the bottom?
Gear lube is thick, I can't see it gushing even when warm, more like oozing out.

haraldpost

I drove the car 15 minutes to get to the workshop, and tried not to waste much time before draining the oil. The brake bleeder tool I used looks exactly like this mityvac fluid extractor.



But I was not able to insert a tiny plastic hose into the bottom of the pumpkin. I tried several different hoses.