Product Reviews

034 Motorsport Rear Diff Carrier Mount Insert Kit

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I’ve had the recently released 034 Motorsport Rear Differential Carrier Mount Insert Kit installed my B7 S4 for about a month now, and wanted to share with my readers what an awesome part it is – I can’t recommend it enough for how great the price is relative to the impact. The part fits B6/B7 Audi A4, S4, and RS4s and costs just under $100, an can be installed in under an hour. The part works regardless of whether you have an OEM or aftermarket rear diff mount, and in fact it compliments my Apikol rear diff mount quite nicely – between the two of them, the driveline slop is practically gone and shifts are so much smoother! This is a mod I’d strongly recommend for any B6/B7 S4 owner, especially those with manual transmissions who have always found shifting a bit jerky like I have.


The mount is made of billet aluminum and firms up the OEM bushing which is rubber, thus taking a lot of play out of the equation and making shifts and power delivery much smoother. You can feel this in each shift, as well as whenever the rear differential is working hardest such as power-slides and burnouts. It’s amazing that such a small part has such a big impact, but it really does!


Installation instructions are provided by 034 on their website, but are a little bit trickier than they sound – while in theory it is as simple as loosening two bolts, slipping in these inserts, then tightening the bolts back up, it’s a bit of an awkward area to get to, which is complication #1. Likewise, the inserts and the locking washers fill a lot of empty space, so it’s a very snug fit and difficult to push them in all of the way. The trick here is to use a lubricant on the insert and OEM rubber bushing so that you can push the insert in as far as possible – a little persuasion from a crow bar or long screwdriver might help too. If you just try to force the insert with your bare hands, you probably won’t be able to thread the nut onto the end of the bolt, as the bolt probably won’t reach. You’ll also need two 18mm wrenches, which aren’t the most common size in the world (I have two sets of sockets and neither had 18mm, jumping from 17-19mm). If you are going to order the tools to DIY it, here is what I’d suggest:

All in all, this is definitely a highly recommended mod regardless of whether you have a heavily modded car like mine or just starting out – it’s one of the best bangs for the buck I’ve experienced on this car, and the fact that its noticeable in both spirited driving and daily driving makes it a huge win in my book.

Thanks again, 034 Motorsport!

Nick Roshon

Nick has been an Audi owner and fanatic for the last 10 years, and started Nick's Car Blog in 2009 to share DIYs and pictures of his A4. Currently he drives a 2012 Audi TT-RS, and has previously owned a B7 S4, B7 A4, and an 82 Audi Coupe (GT) LeMons race car. In his day job, Nick is a digital marketer and lives in San Diego, CA, USA.


  1. It can fit auto or manual Joey – it will just make a bigger difference for manuals since the shifting is inherently rougher when humans do it 🙂

  2. Do you recommend 034 over ECS? 034 seems like one should upgrade the bushings too while at it (i have 90k) but I think ECS comes with new poly bushings. I have the Apikol to install too. I do worry about vibrations.

  3. I tend to prefer 034 all things equal, they engineer things in-house and have always done well for me and the Audi platforms they support. I’m not familiar with the ECS offering, but if they seem comparable then sure.

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