Further chassis stiffening, AKG Motorsport shifter and 3.91 gears installed in my BMW E36

There’s just time to address a few more things before the 2019 autocross season kicks off. Quite a bit of miscellaneous items but they will all definitely impact the car’s performance. This upgrade session is focused on the following areas:

  • Adding more braces to the E36 to further stiffen the chassis front and rear
  • Changing the rear limited slip differential ratio from 3.15 to 3.91
  • Installing a chassis mounted short shifter

Let’s dive in!

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Only a few BMW E36 models came from the factory with the front X-brace installed under the engine to stiffen the chassis. Most models were equipped with a simple bar that connects one frame rail to the other behind the engine (as seen at the top of the picture above).

Obviously, installing the X-brace will stiffen up the front chassis to a certain degree as well as offer more protection to the engine oil pan. I actually went as far as installing both the original simple brace and the X-brace at the same time. There are enough mounts already present in the E36 to do this.

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The only real trick to installing the X-brace in an E36 not setup from the factory for one is the need to install nutserts into the front subframe. You’ll need 6 nutserts total installed in order to mount the front of the X-brace. I found a pretty simple kit online at BimmerBum that I highly recommend, I’ll provide the link below. Install was easy after the nutserts were installed.

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I then installed a rear chassis reinforcement bar that ties together the rear shock mounts. There’s definitely no load coming from the shock mount towers (like the front strut towers) but this will theoretically help to stiffen the rear chassis. Since the bar is so light and I don’t have a rear cage, why not throw this in there??? Every little bit helps.

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I went with the Megan Racing rear bar as I was impressed by the quality of the front bar that I was already running from them. The rear bar is just as well built as the front and was a simple install. I just had to slightly modify the Ground Control shock mounts to eliminate interference with the bar.

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Though the Vortech supercharger is giving my E36 great power now, it still lacks in the low end as I previously noted. That’s just part of the expected performance delivery when it comes to a centrifugal type supercharger. But there’s an easy way to increase low end torque, just change to a numerically higher ratio limited slip differential. After researching the various E36 ratio differentials that I could simply swap in, I decided to go with a 3.91 ratio. I found a used one locally through Craigslist and swapping it in was pretty easy as I had done this previously (check out a previous post for details). Luckily, no issues were encountered during the swap.

After driving the car with the new 3.91 installed, it was a night and day difference! Where before I couldn’t spin my tires in 1st gear even if I dropped the clutch at 4,000 rpm, now I can spin the tires through all of 1st gear and part of 2nd gear. And this is with my sticky Bridgestone Potenza autocross tires!

There’s no doubt that I’ll need to shift into 3rd gear in every autocross now as the ratios per gear are so much shorter. For instance, 2nd gear tops out at about 47 mph now instead of about 60 mph. This is a small price to pay for the urgency that my car now blows through every gear from just off idle! This was just the ticket to make up for my high altitude power loss.

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In order to make my shifts easier, since I’ll be making more of them now, I decided to install a short shifter. I read all about the normal short shifters where you’re basically just changing the shift rod but keeping pretty much the same shift carrier, bushings and relative architecture. I decided to bypass all those stock type replacements altogether and go right to a chassis mounted shifter. The stock shift mechanism (and all aftermarket types that follow the same architecture) have compliance built into them to cope with the movement in the stock rubber engine and transmission mounts. Since I have solid engine and transmission mounts, I don’t need any compliance in the shifter mechanism and can thus mount it directly to the chassis. You can see the stock shifter mechanism on the left in the picture above and the chassis mounted AKG Motorsport Stage II shifter on the right side.

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The AKG Motorsport Stage II shifter is a very solid piece of engineering with no noticeable compliance in the mechanism. It mounts to the E36 chassis with a solid aluminum plate and has a spherical bearing for the shifter rod.

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Seen above is a view from under the car and looking up that shows the placement of the shifter when mounted properly in the chassis. The stock BMW selector rod is shown mounted to the shifter in the photo.

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Here’s a view of the AKG shifter mounted in the stock console. As you can see, it mounts in the stock location and you can even reinstall the stock boot (like I did, though not pictured).

UUC Comparison

When installing the AKG shifter in the car, I did note that the stock BMW selector rod (which connects the shifter to the transmission) had some play in it. After researching this rod further, I saw that many companies offer a better designed replacement bar. UUC Motorwerks appeared to be the best of the bunch. The picture above does a great job of showing the difference between the stock rod and the UUC rod.

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With the new UUC selector rod installed, there’s much less side to side slop of the gear shifter when in a gear. Everything just feels tighter and it will allow me to be more precise when making gear changes.

With the winter upgrades finally complete, it’s time to get this beast out on the track!

Website Links:

UUC Motowerks DSSR Selector Rod

BimmerBum X-Brace Install Kit

Megan Racing Rear Bar

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