Rear Diffuser & Spats

MK7 Alltrack

Tools needed:

Diffuser Install



1.Put the car on flat ground, in park, or first gear with the ebrake engaged. Jack up the rear of the car with a floor jack or bottle jack using the rear jack points. Place jack stands or cribbing under the control arm. Remove the rear tires. It is good practice to place the tires under the pinch seam of the car as a safety measure if a jack stand moves or fails. 

2. If you are also installing spats, remove the T25 torx screw at the rear of the wheel well. If you are not installing spats, skip this step. 

3. Remove the two T15 torx screws that hold the snap clips into the bottom center of the OEM valence, then gently pull down to pop out the clips.

4. Locate the 4 fins.  You will have two fins that are larger than the other two, the larger fins should be in the center two slots, and the angle bracket should be on the outside edge. 

5. Locate the baseplate. With the machined pockets of the baseplate facing up, slide the fins onto the baseplate until they lock into place. The fin hole should be on the top.  

6. If you are having a hard time getting the fins to click in, hold the baseplate against your chest, then grip the fin with your hands and pull it towards you to press it into place. The brass threads on the baseplate should line up with the hole in the fin. The fins have some adjustability forward and back to line them up with the retaining screw. 

7. Install the black M4 bolts using a Phillips head screwdriver. You can use thread-locker on these screws, however it is not necessary. They just need to be snug, do not over tighten. Fasteners this small can be easily stripped. 

8. Locate the M6 bolts, and nuts in the hardware bag. Grab your clamps, a 4mm Allen key, 10mm wrench and a drill with the 6mm or ¼” drill bit. 

9. Hold the baseplate and fin assembly tight to the valence with the countersunk holes facing down. Place a clamp on each edge where the baseplate has a tab sticking forward to keep it in place. Now adjust it left or right to center it. Check the outside edges to make sure that your are lined up all the way around. 

10. Check that the center fin brackets are tight to the inside surface of the OEM valence.

11. Wear safety glasses and drill the two center holes with a 6mm or ¼” bit using the baseplate as a guide. The drill needs to be at an angle relative to the bottom of the diffuser. The goal is to drill perpendicular to the bottom edge of the OEM valence. 

12. Slide a plastic angle shim onto the long bolt, then through the baseplate and valence. Then reach behind the valence and thread on a nut. Hold a wrench on top, and turn the bolt with the Allen key. 

13. Drill the remaining outer holes in the baseplate, and install the hardware. Again, making sure to drill perpendicular to the OEM valence surface. Add the angle shim to the bolt then press through the hole and reach behind the valence and install a nut. (no image, same process as step 11 &12. 

14. Hold the diffuser assembly up tight to the valence. Check that the top edge of the fin is tight to the OEM valence and mark the location of the two angle bracket holes on the OEM valence. Silver sharpie works well. 

15. Remove the two center fins, and drill the 4mm hole for the angle bracket. Reinstall the fins, and install the small m4 bolt and nut to retain the bracket. 

16. Reinstall the clips that hold the bottom of the valence in place. Align the valence, press in the base of the clip, then thread in the T15 plastic screw. 

Spat Install

12. The spats are left / right side specific. The countersunk holes will be on the bottom. The wide end of the spat should be closest to the wheel well

13. Slide the longer included torx screw through the fender washer, then through the non-countersunk hole in the spat. Add on a spacer, then thread into the OEM valence. Just get this started for now. 

14. Repeat for the other two bolts, this time using a countersunk bolt, slide through the spat, add a spacer, then slide into the existing holes in the bumper cover. Thread on a nut. Once all 3 are installed, tighten each down until the spacer is tight to the bottom of the bumper cover. Repeat for the other side.