View Full Version : DIY: B6 A4 - Installing the B6 (ARDU) Apikol Rear Diff-support Upgrade

02-13-2009, 05:10 PM
The standard A4 B6 rear differential mount is good at what it was made to do. That is to dampen the torque placed on the rear differential housing in on-off throttle input situations. However as we start to stiffen up the following:

1) Snub mount
2) Engine mount
3) Tranny mount

Add the following performance enhancements:

1) Upgraded clutch
2) Short shifter
3) Chip and/or turbo mods
4) Intercooler

It becomes apparent that there is a lot of moving around going on back there as you transition from on to off throttle or release/take up the clutch. I experienced this myself last year with only the upgraded mounts. It only became worse with the more powerful clutch, short shifter and my stage 1+ flash. I immediately started looking for an upgrade for the rear differential mount – long story short: never found one. The only ones I saw were for the B5. Then in Aug 2008 browsing the Apikol site I saw a pre-sale going on for the B6 rear diff mount. Throwing caution to the winds I ordered at once knowing that there would most likely be an intro-sale. The mount arrived in Sep 2008 and sat in a box till Jan 2009. Fast Forward to today the day of the install.

Time for Install: 1-2 hours depending on facilities, experience, & working speed.

Tools Needed:

Socket wrench(s)
#6 Hex socket – I prefer the type with the attached socket adaptors
16mm Socket
Locking pliers
Various extensions
Jack + wood (I used several layers of cardboard)
Ramps/Jack Stands/Floor lift
Blue loctite
Shop light (Whatever works, its dark and cramped under there.)
Penetrating oil



Disclaimer: Okay now remember if you do not know how to take care of yourself under a car have the installation performed by an experienced mechanic and just read this for informational purposes only. Drinking and driving are not encouraged. Use due diligence when working on your whip. U will be working near exhaust parts allow sufficient time for them to cool properly preferably overnight.

Steps to Swap out B6 Rear Diff Mount:

1) Raise car up so you have access to the rear differential (I used my ramps and just backed up onto them) Stop, relax and crack open a beer, Rockstar, or other beverage of choice.


2) Using your jack and a block of wood (in my case cardboard) support the front end of the rear differential as shown in the pictures below. Only raise the jack enough that it is snug up against the differential. This will help to make loosening the bolts sooo much more easier.



3) Here is your stock diff mount:


Using your #6 hex socket and a socket wrench remove all 3 of the hex bolts. I started with the bolt closest to the front and worked my way to the back of the car. At this time you will want to ensure that the jack is indeed snug up against the differential because with the removal of the last bolt the jack will be supporting most of the weight of the front part of the rear differential and the rear part of the driveshaft.


4) Loosen the single 16mm nut holding the bushing of the differential mount. Mine broke loose relatively easy but it is possible for both the bolt and nut to turn together. If this happens just use the locking pliers to hold the end of the bolt while loosening the bolt. If you are using ramps like I did there is not a lot of room under there but it can be done. Also if u live in a state that salts the roads during winter this nut might be rusted on there. Give it a few squirts of penetrating oil and allow it enough time to break through the rust before trying again. Here is the stock diff mount hanging free


5) Carefully lower the rear differential out of the way of the differential support by slowly lowering the jack. Roll, move jack out of the way – I found out that the jack can be totally removed out of the way to make the next few steps easier.

6) Remove the 16mm nut and its washer. Use one of the hex bolts to push the long mount to sub-frame bolt partially out of the stock diff mount and leave in there to support the diff mount. Move around to the other side and pull the mount to sub-frame bolt out the shorter hex bolt should now be holding the stock diff mount in place but be prepared to support the diff mount in case it falls out. Here are both mounts side-by-side; sorry for the shadow in the pics but you get the idea of how much more support is offered by this bushing than the stock one. It is completely filled in with a much more stiffer material. Relax here and have another beer, Rockstar, or beverage of choice and mentally compare the pieces and prepare yourself for the improved shifting and more solid driving feel you are about to experience.



7) Here is the hardest part of the install and where I hope others will learn from my folly. Using one of the HEX BOLTS from the driver’s side of the car place the bushing end of the Apikol rear diff mount in its location as shown in the pic below.


Moving to the passenger side of the car with the long mount to sub-frame bolt with its associated washer in hand “attempt” to locate the hole on the passenger side of the sub-frame to diff mount. When ready to insert the bolt/washer ensure that the bushing is centered in its position using your other hand if not, you might use 30 minutes like I did trying to push the mount to sub-frame bolt in the hole that is blocked by the edge of the un-centered Apikol rear diff mount bushing hole. When you find the hole push the mount to sub-frame bolt all the way in to be rewarded by the tinkling of the hex bolt falling out of the other side.


8) Place the washer on the mount to sub-frame bolt and apply blue loctite to the bolt. Loosely tighten the 16mm nut leave it loose enough to wiggle around.


9) Moving your jack and wood/cardboard combination into place raise the rear diff up to the level where the 3 hex bolts can be re-inserted into the side of the differential. I found it easier for you to actually start at the rearmost bolt first and physically move to the side to visually ensure that the bolt hole of the Apikol diff mount is perfectly lined up to the hole on the side of the diff. Apply blue loctite to the end of the bolt and insert in hole. Do not tighten leave it loose enough to wiggle around. Do the same for the middle hole and then finally the front most hole on the diff mount adjusting the jack each time to ensure the holes are centered.


10) Tighten the 3 hex bolts starting with the one closest to the front of the car to “35lbs.”or ”good and tight” according to Brian at Avalon Motorsports - maker of the Apikol rear diff mount. I then tightened the mount to sub-frame nut last. At some point the bolt and nut will start turning together. Using the locking pliers hold the bolt in place while getting that nut on there “good and tight”.


Move back a little and marvel at the beauty of a much more solid rear diff mount and the install money you just saved.



11) Take car out for a spin and enjoy more solid shifting and more importantly no more rear end diff clunk.

Thanks to:
Brian @ Avalon Motorsports for replying sooo quickly to my email.
My girlfriend Kat for having dinner hot, perfectly timed and ready for me late when I finished this install and a quick shower.