I have a small leak under my 02 A4 in the rear. I'm not sure if its the trans pan or diff cover. I want to check the fluid levels and top off if necessary. I'm sure it has Dex III in it. I know Dex VI is compatible. My question is SYNTHETIC or CONVENTUAL?

 

Synthetic is fine for '02.

 

The engine MUST be running transmission in park before removing the fill/ check level plug on an A4.

Changing or checking the fluid and filter on a C5 A4 is fairly easy, but there are specific procedures to insure that the fluid level is correct after changing or checking:

After replacing the filter and bolting the pan back up, fill with new fluid to the drain/ check level plug hole. Then start the engine and leave it running with the transmission in PARK.

Immediately add fluid through the drain/ check level plug hole until fluid flows out of the plug hole. It may take as much as another couple of quarts.

With your foot holding the brakes, cycle the transmission through all the gears, then back to PARK.

Go back underneath and make sure that fluid is still dribbling out of the fill/ check level plug hole. You might have to add some.

With the engine still running and the transmission in PARK, monitor transmission temperature on the DIC. When transmission temperature rises to 122 F, put the plug in the fill/ Check level hole. Keep a pan under the hole, fluid will dribble out as the transmission temperature rises.

Do NOT shut the engine down until the plug is in the fill/ check level hole. If you do, HOT fluid will gush out and the transmission will be low on fluid.

I recommend full synthetic fluid.

Keep in mind that the above procedure drains about half the fluid in the A4. The other half is in the torque converter and other works.

You will need a small hand pump to pump the fluid into the fill/ check level hole.

 

Thanks for the replies. I assume synthetic is ok for the gear oil? I’m not draining it either just topping it off.

 

Yes, synthetic gear oil is good for the rear drive.

 

I don’t know about auto trans oil but synthetic is not recommended for the t56 z06 trans

 

I had my trans flushed and serviced last summer by my local Vette shop (Tony's!) We used AMSOIL 100% synthetic OE trans fluid and AMSOIL 100% synthetic 75-90 GEAR OIL in the fresh 3.42SP rear I had installed at the same time. Brand of your choice of course, but SYN is fine in the A4's-I am sure the updated Trans tune (for the 3.42 rear) helped but it runs and shifts smooth as silk-

 

I'm not changing at this time, I've been advised not to change it if I didn't have service records. I have a tiny leak in the rear of the car and can't tell if it's the transmission pan, axle seal or the diff cover. I'm going to clean all of it up and check fluid levels and top off if needed.