Katarina Gets the Iron Out

I've got 2 huge addictions when it comes to cars.   Speed and individualism.  So lets put a lightweight flywheel in and see if we can get those acceleration lowered a notch.   The following pictorial will walk you through putting an Active Autowerke lightweight flywheel into my '98 M3/4.  It weighs 12 pounds.  I also bought an E34 535 bearing fork from AA on Mike Hugh's advice.  It keeps the clutch release point high instead of on the floor.  The fork cost $12 from AA.   No brainer.  Some people have said there would be several problems possible when adding the flywheel:

Unstable idle, possibly stalling Nope.  750 RPM just like before.   My car is Sharked, but no increase programmed in by Jim Conforti.  No stalling when returning to idle from speed.
Incorrect mounting hole diameters on crankshaft mounting points Nope.  The holes are exactly the same.   The locating dowel hole is perfect too.  Fits like a glove.
Clutch release point is all wrong True.  Unless you use the shift fork from the E34 535 as recommended.  Do it.
The flywheel will be noisier True.  It makes a slight rattling sound at ~2500 RPM on light acceleration and deceleration.  I believe this is caused by the new aluminum unit NOT being a dual mass unit.  It won't hurt anything.  Its just a peculiarity of the beast.


Enough talk.  Lets see the pictures!

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Well here's the victim.  Looks like she hardly suspects a thing.  Notice the JTD Transmission brace.  Here's my friends from Bavarian Mastercare in San Marcos, CA, Hammed and Habib, dropping the exhaust.  The front section of driveshaft has to come down too.  Live in San Diego County and need some work done?  They're good and they're fair.  Recommended.

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Like I said, drop the driveshaft off the transmission.  You'll need to drop the center support too.  The insulation was removed right after the exhaust.  Disconnect the clutch slave cylinder, the electronic connections and the shifter linkage.  Yep.   That's one of those God-awful expensive AC Schnitzer linkages.  Buy Ben and Rob's, it works just as well.  I bought just before BL/SS was available (Thanks to Suzy and her sister from the E36M3 list).  Start pulling the reverse Torx bolts to get the transmission out.   A 3 foot extension helps.  Especially for the starter mounting bolts.

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How's the throwout bearing?  Mine's fine.  The picture on the right shows the old fork (well that's what it is on a Chevy anyway and that's what I always called it.) that needs to be replaced with a $12 E34 535 piece to maintain the proper clutch release point.   Note you might have to put a jack under the front of your engine to tilt the back of the transmission down to get it out.

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There's the pressure plate.  Remove the hex bolts holding the pressure plate on with a hand impact.  DO NOT USE AIRTOOLS!  Airtools will likely strip the heads of the hex bolts, they're soft.  Get a hammer and a hand impact.

Now you can zip those mounting bolts out with an air impact so you can get the flywheel off.

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New one is at the bottom, old one in the middle and the clutch disk/pressure plate at the top.   Inspect.  Mine was good enough to put all the stock parts back in again.   Be forewarned, the clutch disk and throwout bearing aren't stocked items, at least anywhere in San Diego county.  Order ahead of time and be prepared.

Well there she is, ready for reassembly, which, as they say, "is the opposite of removal".  We need to talk about a couple of things.....  This job is best left to pros with the proper tools.  Mine took 4 man hours.  I've heard horror stories from others seeking quotes.  4 hours.  Really, 4 hours.   Also, while the folks at AA are terrific, the instructions I received were accurate but out of order.  I've talked to Mike and let him know where I had questions.  He said he would take care of it in future shipments.  If you buy one and your instructions say to attach the flywheel to the pressure plate before bolting to the crank.... ummmm, no.  The other thing is that the engine compression is not going to hold the crank while you torque the flywheel to 80 ft/lbs.  You either have to hold a socket on the crank at the front of the engine or use a flywheel clamp or jam a screwdriver in the ring gear and hope it doesn't break the teeth and wreck your day.

Keep your transmission laying upright when it's out of the car.  As you can see in the photo of the 2 flywheels on the ground above, I dribbled some Redline MTL out rolling the transmission around looking at it.  Its a ZF, BTW.

So, does it run quicker?  Oh yeah!  Before installing the flywheel, I could floor the car while idling at a couple of miles per hour and it would lug up to about 1200-1500 rpm and then take off, pulling away strongly.  Two days after installing the lightweight flywheel I tried this little experiment again.  Result?  Two black fingerprints from my 255/40-17 Michelin MXX3s 50 feet long.  Yippee!  Some people that seem better than me at physics calculated the affect on the car as an equivalent drop in vehicle weight of ~250 lbs. in 1st gear and ~90 in second gear.  Whatever the actual numbers, it is certainly, clearly worth it in my mind.

That's it.   Feel free to email me  if you have any questions.