Nov 13, 2009 update to the BMW M3 project car

Fresh Friction

The ACT Clutch and Flywheel kit was very complete.
Here's our disengaging Autosolutions short shifter.
Exhaust and heat shielding removed, drive shaft disconnected.
BMW superhero Rennie Bryant lent a hand.
Here, we're removing the transmission. It took some rocking to get it free.
An air chisel was needed for the job. Fortunately, the ACT kit came with new fasteners.
New vs. old--new wins!
We removed the heavier stock flywheel.
Here's our rear main seal and crank.
Our new flywheel saved over 8 pounds.
We replaced the rear main seal.
We matched the crank marker to the flywheel.
Ooh, here's our shiny new flywheel.
Al in and ready for reassembly!

The car is still easy to launch, suffers from no increased noise or vibration, and is refined in all situations.

Sometime, somewhere, someone said, “To all good things there must come an end.” Although it is doubtful the person that coined this phrase was talking about the clutch on an E36 M3, in our case they could have been. We first noticed the clutch was getting a bit weak a while back—when we were doing zero-to-60 testing on the trusty BMW. Usually, dropping the clutch at 4000 rpm would incinerate the tires, even the sticky Yokohama Advans we had on that day. Instead, we heard the engine revs climb, and the sickly smell of clutch material filled the car. We knew that time was running out for the stock clutch.

To be fair, the stock piece held up incredibly well. It had withstood 135,000 miles, multiple track days, autocross launches, and even a few trips down the drag strip. Although it was still usable in day-to-day driving, enthusiastic full-throttle upshifts also resulted in a bit of slippage. It was time.

Fortunately, the aftermarket is full of performance parts for the E36 M3. We had always heard good things about Advanced Clutch Technologies clutches and flywheels, but we’d never tried one in a European application. ACT has been known for years in the Japanese tuner scene, and recently they have added a large number of European cars to their parts catalog.

While we were changing the stock dual-mass clutch, we decided to install a lighter flywheel to reduce rotating mass. When it comes to driving fun, a lighter flywheel can pay great dividends. More immediate throttle response and a more eager run to the redline are typical benefits from installing a lighter, aftermarket piece.

Unfortunately, clutch “chatter,” difficult launches and other drivability problems can also arise from switching to a too-light flywheel. As the M3 is mainly a street car, we decided to run the middle ground and opted for a Street Light 14.8-pound flywheel. We hoped it would be light enough to increase our fun factor without ruining the smoothness the BMW is known for. Also, the switch to a lighter rotating assembly, coupled with the solid disk in place of the stock dual-mass clutch, would shed some pounds.

Although the brave among us may be willing to tackle a clutch installation at home, hopefully that home would have a lift, a transmission jack, an air compressor, and all the tools needed for the job. Our home away from home was Redline BMW in Pompano Beach, Fla. Rennie Bryant, our favorite BMW guru, has performed dozens of these installations. He lent a willing hand—well, both hands—to help us out.

Once the M3 was in the air, the first step of our operation was to clear the underside of the car from all of the components that would be in the way. The entire exhaust system (aft of the downpipe) was removed, along with the heat-shielding material covering the driveshaft tunnel. While we were at it, the subframe bracing was also removed, the driveshaft was disconnected, and the Autosolutions short shifter was disengaged. The top starter bolts proved to be a chore to reach. A very long socket extension was used to access them; we approached it from the rear of the transmission. Having an assistant guide the socket onto the fastener was a big help in getting the job done. This also was true when we disconnected the bell housing fasteners.

Once all the bolts were removed, the transmission slid out and was free from the car. As our car’s transmission and engine had never been apart, it was difficult to remove the two, but gentle rocking gradually separated the assemblies. Dropping the fancy BMW’s transmission on the ground would have really ruined our day, so we took extra care in the separation and lowering process.

Now we were staring directly at the pressure plate and clutch assembly. We deliberately removed the pressure plate fasteners, as they strip easily. Even with the extra care, a few of them became rounded off, and we needed to use an air chisel to remove them. Fortunately, new fasteners were included in our ACT kit.

Finally our worn clutch was visible. The old unit was clearly in need of replacement, but it had held up well considering its long-term use. With the car all apart, it was a good time to clean as much of the assembly as possible. It was dirty, nasty work, but soon the bell housing and input shaft were gleaming and ready for the new pilot bearing and reassembly.

While the car was apart, we decided a bit of preventative maintenance was in order. We replaced the original rear main seal with a fresh unit. The reassembly was pretty straightforward. We took care to line up the marked point on our crank to the flywheel assembly to make sure all was aligned properly. We used the clutch alignment tool provided by ACT to make sure the assemblies mated together smoothly and perfectly. While we were under the car, we also changed the 12-year-old fuel filter with a fresh unit. We then filled the transmission with Redline ATL synthetic oil to ensure smooth shifting for years to come.

Fortunately, our BMW didn’t pull a Humpty Dumpty, and all the pieces fit back together without issue. Finally, we could take the car out for a test drive!

Our M3 has always been a satisfying machine to drive. However, thanks to the reduced rotating mass of the new ACT flywheel and clutch, it really chomps at the bit. The car is more eager in all driving situations, with improved throttle response across the rev range. It actually feels faster.

The best part is that the improved performance came with basically no downside. The car is still easy to launch, suffers from no increased noise or vibration, and is refined in all situations. We haven’t abused the car, as ACT recommends a break-in period of a couple hundred miles. Once the break-in period is over, however, we plan on taking the M3 to the track to see if the seat-of-the-pants improvement in performance is measurable.

Evidently, good things coming to an end sometimes leads to even better things in the future.

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