4.0T Downpipe Installation

Thank you for purchasing from ARM Motorsports and congratulations on your new 4.0T Downpipes! 

For this install you will need:

  • A Jack and Stands
  • A Socket Set (10,12,13mm) and Ratchet
  • 10mm Triple Square Socket
  • 22mm O2 Sensor Socket
  • T25 Socket

Step 1

Pull the weather stripping off of the plastic cowl over the rear of the engine bay. You can do this by pulling it towards the front of the engine, off of the lip on the rain tray. Then remove the rain tray and engine covers.

4.0T Downpipes Installation

Step 2

Disconnect the negative battery terminal with a 10mm socket. This will ensure there are no shorts.

Step 3

Remove the strut tower brace by removing the 7 bolts holding in.  


Remove the 2x bolts fixing the strut tower brace on each side.

Step 4

Strut tower brace removed. 

4.0T Downpipe Installation

Step 5

Move to the electrical junction box attached to the top of the bulkhead. Unscrew and disconnect the 2x ground connectors, 1x 10mm and 1x 13mm. Pull the harness up and out of the way. Look to the electrical connection to the left side, unclip this and pull the entire harness out of the engine bay.

Step 6

Take the 2x 10mm nuts out holding the junction box in place. Then move the box out of the way.


Step 7 

On the back side of the bulkhead, pull out the vacuum booster line from the rubber grommet. Pull the rubber fitting out of the bulkhead.

Step 8

Take off the metal clip on the top of the threaded stud.

Step 9

Peel back the heatshielding to uncover the 10mm nut underneath and remove.

Step 10

Label each O2 sensor post/pre cat and driver/passenger. Then remove them from the downpipes with a 22mm socket.

Step 11

On the left side, pull back the heat shielding to uncover the 2x T25 screws and remove.

Step 12

Take note of how the bulkhead is fixed to the firewall, then remove.


Step 13

Now underneath the car, remove the 3x T30 fasteners on the underbody pan. There will also be 7x quarter turn fasteners that will need to be removed as well. Then pull the pan and set aside.

Step 14

Loosen the 2x 13mm nuts on each exhaust sleeve at both midpipes.

Step 15

Take the 3x 12mm nuts off each flange of each side exhaust from the midpipe to downpipe. 

Step 16

Loosen the 13mm bolt from the brackets on the transmission to the downpipe.

Step 17

On each turbo there are 5x 12mm nuts that need to be removed.

Step 18

Remove both downpipes from the engine bay. Lowering the right downpipe and then working out the left tends to be the easiest path.

Step 19

Set in each ARM Downpipe (start with the left for ease) with supplied gasket and nuts. These can be torqued down to 17 FT-LBS.

Step 20

Find both the pre and post-Cat O2 sensors that are part of the right side harness. Place the Pre-cat O2 Sensor back in the location closest to the turbos.

Place the post-cat O2 sensor in the location farthest from the turbo ON THE SAME SIDE (This is where you will place the CEL Kit if you are using that from us).

Even though the original downpipes did cross over, the post O2 sensor is simply reading for catalyst efficiency, not to determine fuel trims, and can be placed on this side with out issue. This will negate the need for a harness extension.

Step 21

You will then perform this same process for the left side.

Step 22

Use the included midpipe gaskets and bolts to loosely connect the midpipes to the downpipes.  They will be fully tightened after the brackets have been mounted. 

Step 23

Go back to the stock Downpipes and remove the 13mm bolts that are part of the spring bracket (the right and left side do look different).

Step 24

The left downpipe bracket will be flat, and can be attached to the left side of the transmission with the 13mm bolts

Step 25

Install the right side bracket in the same fashion. 

PRO TIP:  On some vehicles the brackets will line up better when flipped in the opposite direction.  Orient the bracket so that it lines up correctly for your vehicle.

Step 26

Now all 6 midpipe bolts can be tightened all the way down.

Step 27

Reinstall the Belly Pan

Step 28

Reinstall the bulkhead, and make sure the bottom is in its normal position. This must seal.

Step 29

Replace the 10mm nut from underneath the heat shield. Bend the heat shield back and put the metal clip back to hold the shield in place.

Step 30

Reinstall the T25 screws under the heatshield on the right side of bulkhead.

Step 31

Place the rubber grommet back into the bulkhead. Reinstall the vacuum line.

Step 32

Flip down the junction box and secure it back in place with the 10mm bolts

Step 33

Reconnect the ground straps in the junction box with the 10mm and 13mm nuts, respectively. Plug in the wiring harness.

Step 34

Place the strut tower brace back with any of the brackets that were removed at the beginning. Secure this down with the 5x 10mm triple square bolts to 177 in-lbs. Put the 2x T25 bolts back in, holding the bulkhead to strut brace.

Step 35

Install the rain tray weather-stripping supports on both sides of the
bulkhead. Secure with the the plastic push-clip and 10mm plastic nut.

4.0T Downpipes Installation

Step 36

Reinstall the weatherstripping, and reinstall the
engine cover.

Step 37

Reconnect the battery

 Your 4.0T is now equipped with the ARM 4.0T Downpipes!  Enjoy the new sounds and power, and check out our other Performance Parts for your 4.0T Powered Audi!


Net Orders Checkout

Item Price Qty Total
Subtotal $0.00

Shipping Address

Shipping Methods