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Date: Sat, 27 Feb 1999 22:12:37 -0600
From: Paul Hahn <>
To: bmw Mformation <> Subject: M635 rebuild - put that tranny in


With the engine sitting on it's two mounts , it has as a natural tilt down towards the rear - perfect angle to mate the gear box up. Install a new pilot bearing and then the flywheel . Sandwich the clutch disc between the flywheel and the pressure plate and start the bolts but don't tighten. Use a disc locating tool to align the disc centered in the assembly so that the splined shaft of the tranny will slide through the disc and then into the pilot bearing. I did a trial fit of parts while the gearbox lay on the floor to assure myself that the disc would fit on the splines and that the tip of the shaft would fit into the pilot bearing. That way if there was a part problem I could remedy it ahead of time and if i had trouble later on getting the tranny to mate, I could be assured that it was due to a misalignment of the disc. Use some thread lock on the bolts that hold the flywheel to the crank and the bolts that hold the pressure plate to the flywheel. Clean the surfaces of the flywheel and the pressure plate with some brake cleaner and avoid putting dirty fingers on any of the friction areas.

In the bell housing of the gearbox lives the throw out bearing (put in a new one) and the clutch actuator arm which is held in place on one end with a spring clip. After you get these in place it's time to put the gearbox (put into any gear- NOT neutral) on a lifting device (i used a hydraulic floor jack) and raise it towards the flange of the block. Move slowly and notice that when you get to within two inches you'll feel some resistance from the tranny shaft fitting through the disc. Stop here and rotate the output of the tranny which will allow the input shaft to "find" it's splines in the disc. When the tranny output will no longer turn by hand , proceed with pushing it closer to the block and when it gets close enough , start two of the mounting bolts and use them to pull the two together with LIGHT turning force on the bolts. Check the top , bottom , and both sides of the gap between the tranny and block to keep the tranny "square" to the block. If the disc is properly centered in the clutch assembly , the gap will close to zero with ease. Install the rest of the mounting bolts, torque them all and jack the rear of the tranny up to install it's support. Now you can install the shift mechanism and the "back-up" light wires. I put on a new guibo and a new center carrier bearing as i re-installed the drive shaft. If your diff support is sagging , this is an excellent time to replace it. Check for sag by lifting the diff with a floor jack - if the whole vehicle raises with the diff then the support is ok. If the diff moves an inch or more before the car moves , it's worn out. Put the heat shield up against the underside of the car and install the exhaust system - again i used a floor jack to hold it up while i connected the support devices. Renew the rubber parts if in doubt about their quality. Don't forget to reconnect the O2 sensor wires.

If you need any more detail , drop me a note. I've got all the specifications on torque.


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