Our Project M3 starts in Grassroots Motorsports this month. As part of our grande M-car comparison cover story in the April issue (available late February) we have officially announced and begun our Project M3 build-up series. The stories will contain much more detail than what you see on the Web site (a good reason to subscribe!).
The M3, like most BMWs (and for that matter, most other German cars) uses a Sachs clutch. A stock Sachs clutch is as good as most anybody needs in an M3. By design it is heavy duty in nature and we have used standard Sachs clutches in all our BMW project cars with absolutely no problems. We would be hesitant to put a lesser brand or no name brand in any project car, primarily because of the difficulty involved in replacement. We say difficulty, although replacing a clutch is really pretty straightforward. The difficulty is in getting to it.
In any vehicle we have ever worked on you must first remove the transmission to replace a clutch. Obviously, a lift sure makes this job easier. Once you remove the exhaust system, driveshaft, heat shields and transmission, the job is quite easy (except for putting everything back together again). You simply pull the old clutch disc, pressure plate and throwout bearing out and put new ones in. The pressure plate just bolts to the flywheel and the throwout bearing just slides over the input shaft of the transmission on a sleeve and sits in the clutch release fork.
A few notes when you do this job though… first, always have the flywheel resurfaced. Even if it looks good, you can’t tell how straight it is. Resurfacing a flywheel is cheap and easy at any good machine shop. This would also be a good time to lighten and balance the flywheel if your class rules allow it. Careful on lightening a flywheel too much, as it can effect driveability. You also want to always replace the throwout bearing or bushing and pilot bearing (found inside the crank shaft at the end of the input shaft on the transmission). These items may not be bad, but they cost so little to replace, it is stupid to get all the way in there and not service these items.
Heavy duty clutch kits are also available from Sachs. These items are perfect for club racing or serious school or autocross work. They offer increased clamping force as well as more durable organic racing linings. The Sachs M3 part number for the Sport pressure plate is #88 3082 999 618. The disc is #18 1862 168 132. The heavy duty throwout bearing is part number 05 3151 047 231. This bearing has an aluminum carrier rather than the stock plastic one, so it takes more heat.
As is unfortunately a little too common with big powerful four cylinder engines, the drivetrain in the E30 M3s has an annoying vibration that manifests itself as a terrible shifter buzz between 4000 and 5000 rpm. All M3s have this buzz, it just ranges from barely noticeable to downright annoying. We have had several M3 experts drive our car and all have said that ours has the worst shifter buzz ever seen.
While we were putting in the new Sachs clutch and while we had the transmission out we went to work on the buzz. The problem is so prominent in M3s that BMW has even done warranty work and issued service bulletins in this area. What is odd on these cars is that some M3s do it way worse than others with no rhyme or reason.
Our first attempt at a solution came in the form of installing an Autosolutions shift kit. We have known Autosolutions owner Ronald Aractingi for years and have found him to be very helpful and a great guy when it comes to BMW technical questions. Please understand, that putting a quick shift kit in a car does not by itself fix a shifter buzz problem. But, many of the replacement bushings in a quick shift kit also are needed to fix the buzz. We also do not like the sloppy way that most BMWs, especially when they get older, shift, so we figured we could kill two birds with one stone.
Well, we killed one bird, as once everything was tightened up in the shifter department the car shifted well, but it buzzed worse than ever. Someone on the M3 users group (Bimmers.com) suggested we check out UUC’s web page (http://www.uucmotorwerks.com/), as they have a good technical article on the subject of E30 M3 shifter buzz. We went through all of their recommendations, and just for kicks and comparison’s sake tried one of their UUC shift kits. We liked their shifter kit even a little better than the Autosolutions kit, but still we had the shifter buzz.
Next, we talked to M3 expert Mario Langsten, who made a few recommendations and is letting us experiment with some of his parts. We are almost done experimenting and can happily say that with a combination of all three experts opinions and a lot of help from Rennie at Redline BMW we have this problem about solved.
Our next project will be the fitting of a Mass Air Conversion kit. Designed by Split Second , and sourced from BMP Design, this product replaces the highly restrictive air flow meter. We will be doing before and after dyno runs to see if this innovative product lives up to expectations.
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