In my last installment of ’98 M3 Sedan Overhaul, I covered the work done to the rear suspension and brakes.  Conducted near simultaneously was work on drivetrain, to include the shifter, driveshaft (propshaft in BMW terms), and of course the transmission itself.  As I mentioned in my first post describing the new (to me) car, the shifter was a bit loose.  This is fairly common, usually the shifter carrier bushings which attach the shifter to the transmission are worn out.  In OEM form they are made from rubber, to help isolate vibrations coming through the shifter.  This translates into slightly vague shifter feel, which deteriorates as the car ages.  After reviewing the car’s maintenance logs, it looked as though everything involving the shifter mechanism was still original.

Getting to the shifter parts is the most difficult part of any work performed, as it resides above the driveshaft, which itself is above the exhaust secondary pipes.  My work on the rear suspension had already required disconnecting the rear of the driveshaft and removal of the muffler assembly, so half the work was already done.  I then disconnected the secondary pipes, which contain the catalytic convertors, from the headers.  With the exhaust out of the way I could now drop the large heat shield that covers the central tunnel and driveshaft.  I then disconnected the driveshaft at its connection to the giubo (a rubber flex joint) at the rear of the transmission and also unbolted the center support bearing (aka hanger bearing) to completely remove the driveshaft.  I did inspect the giubo carefully, but it was in surprisingly good condition, no need to replace.

With everything underneath out of the way, I moved into the interior of the car to remove the leather shifter boot, the inner foam sound insulator, and finally the rubber boot that seals off the hole.  The original rubber boot had dried out over time and ripped apart upon removal, add that to list of items to replace.Shifter Boot RemovedBack under the car I could begin to remove the factory shifter bits.  One extra step that provides for much needed working room is unbolting and lowering the transmission crossmember.  This allows the transmission to drop away from the tight confines of the center tunnel, giving you space to access the clip (aka “Bitch Clip”) securing the shifter carrier to the rear of the transmission.  Dropping the crossmember would also give me an opportunity to replace the sloppy hourglass OEM transmission bushings.  These bushings are notorious for allowing excessive transmission movement under high loads and can severely compromise shifting, potentially causing a mis-shift (aka “Money Shift”).  With the tranmission slightly lower I could see that someone had previously attempted some work in the area.  The “Bitch Clip” wasn’t engaged properly and a zip-tie had been looped around it in an attempt to keep it from working loose, what a disgrace.  I snipped off the tie, then easily worked out the loose fitting clip.  I should also mention that the shift selector rod is also disconnected at both ends at this time.  Now with everything disconnected I could remove the entire OEM shifter assembly.

Old vs New Shifter

In the photo above you can see the original OEM shifter parts next to the new Bear Motorsport shifter and AKG billet aluminum selector rod.  Also being installed are a new rubber boot and gearshift rod joint (25117580281), which is an updated design no longer requiring use of the flimsy yellow plastic washers.  The Bear Motorsport shifter is pretty ingenious in its simplicity.  Rather than producing some overly expensive custom piece, it simply uses an M Coupe/Roadster shifter that is bent slightly for use in an E36.  The M Coupe shift is already the shortest throw shifter in the BMW line-up and makes for an inexpensive upgrade to other cars in the E36 family.  The rubber isolator of the shifter has also been crimped down, reducing the flex associated with the factory setup.  While the shifter itself is a customized OEM part, the carrier and selector are aftermarket parts milled from solid billet aluminum.  This provides for corrected pivot height in the carrier, while the selector is now a double-sheer setup instead of the single-sheer of the stock rod.  The selector rod is also made to much tighter tolerances than the factory piece, thereby doing away with the yellow plastic shims.  The tolerances are so tight in fact, that I had to file a bit of material away from the rod joint to allow for a smooth fit.

Bear Motorsport Shifter Installed

You can now see the completed assembly installed.  I added some PFTE (Teflon) grease to the pivot ball prior to installation, then gave all the steel parts a spray of CorrosionX to insure rust wouldn’t creep in.  You may also notice the Bimmerworld cup-style transmission mounts, which are just loosely fitted here.  I already mentioned how the stock hourglass mounts are pretty poor when it comes to securely locating the transmission, so this was a perfect opportunity to upgrade.  The Bimmerworld mounts are still made of rubber (rather than polyurethane, Delrin, Nylon, or aluminum), so they should do a decent job of isolating engine vibrations.  The photos below show the OEM mounts side-by-side with the upgraded mounts as well as the final install.

OEM vs Bimmerworld Transmission Mounts Bimmerworld Cup Mounts Installed

While the driveshaft was out, I took a good look at the center support bearing.  These bearings are suspended in a rubber donut, which means they are susceptible to aging and rotting like any other rubber part.  The metal frame of the bearing was also very rusted and from what I could gather it was an original part.  I happened to have an unneeded bearing on hand, so it might as well go to use.  Replacing this bearing requires separating the two halves of driveshaft, which is easily done by loosening a lock nut then just pulling them apart.  Before doing so, make sure you make a mark on the splines so that you reassemble with the two shafts properly indexed, as the driveshaft should be balanced as a complete assembly.  Once apart you can then remove the external snap ring from the front of the rear driveshaft, this ring secures the shaft inside the bearing.  Behind the snap ring is a metal dust shield that covers the bearing, which you can remove using some thin needle nose pliers.  Now the hard part; pulling the support bearing from the rear driveshaft.  The bearing is a press fit on the shaft, which requires use of a puller or press.  I couldn’t use my hydraulic press due to the length of the driveshaft, so I would have to get creative using a puller.  After a few trial and error attempts, I finally found the right combination, which you can see in the picture below.  To install the new bearing I used a brass drift and a small hammer to work it on, moving the drift around the inner race as I went.

Removing Snap Ring Removing Center Support Bearing

With the car still up in the air on stands, I had a few other priority items to take care of.  One was draining the “Lifetime” transmission fluid.  BMW began using this fluid right about the same time they started including free maintenance and servicing, coincidence right?  Nothing in their fluid specifications had changed, just the fact that you no longer needed to change it.  This, of course, is a complete farce.  There is no such thing as “lifetime” fluid, and you’d be severely shorting the lifetime of your transmission by believing otherwise.  Nothing in the car’s service records indicated the fluid had ever been changed, so I decided to drain it.  I then refilled with Redline D4 ATF, and yes this transmission does call for ATF, despite being a manual.

The other item to address was the clutch, more specifically the clutch line.  Like my M Coupe, the M3 was fitted with a Clutch Delay Valve (CDV) inline with the flexible rubber clutch hose.  This valve is really just a pair of different size orifices within the clutch line that essentially automatically feather the clutch on engagement by reducing the flow of hydraulic fluid out of the slave cylinder.  That’s great if you don’t know how to properly drive a manual and want smooth engagements, but not so great if you want fast shifts or would like to prolong the life of your clutch and flywheel.  Fortunately the fix is fairly easy to accomplish, just requiring replacement of the clutch line with an aftermarket version.  I had a Rogue Engineering stainless line on hand, which has equally sized orifices to allow matched fluid flow in both directions.  The added benefit being that a stainless steel braided line will not bulge and distort like the factory line, which at this point was showing its age.  In the photos below you can see (albeit poorly) the OEM line’s mismatched orifices and the RE line installed.

OEM BMW Clutch Line with CDV Rogue Engineering Clutch Line

The most difficult part of any work on the clutch hydraulics is getting all the air out of the system through bleeding.  I’ve done this job before, and it still is a headache.  I found that, unlike the brakes, the pressure bleeding method doesn’t produce good results.  Many folks will claim that you have to remove the slave cylinder from the bellhousing to properly bleed it.  This misinformation stems from the location of the bleed screw, which points out from the bottom of the cylinder.  Naturally air trapped in the system wants to rise, and a bleed valve on the bottom would not allow for proper bleeding.  The designers of the slave cylinder were a bit smarter than that, as the actual port for bleeding is located at the top rear of the cylinder, which then travels down to the bottom for easier servicing.  You can find photos online of these cylinders cut open, which help clarify the hearsay.  All that said, it is still a complete pain to bleed, especially if your bleed valve is leaking around the threads as mine was.  I had to remove the valve, clean it, coat with thread sealant, then finally bake it on in the oven.  This kept the fluid from escaping around the threads and therefore allowing air in.  So how did I finally get the system bled properly?  By using this simple trick I found on YouTube, which forces fluid in through the bleeder using an oil can to pump fluid up to the master cylinder and eventually overflow into the brake fluid reservoir.

 

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