Genuine BMW M3 Transmission Assembly

BMW M3 Transmission Assembly Parts Questions & Answers

• Exchange 5 Speed (Overdrive) Gearbox
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  Q: How to remove and install Automatic Transmission Assembly?

  A: To remove and install both E30 and E36 models, loosen the throttle cable, disconnect the exhaust, remove the transfer case (for 325iX models), drain the transmission oil, support the transmission, and remove various bolts and sensors. For E36 models, remove the cross member, disconnect the driveshaft, and remove the torque converter bolt.
• Exchange 5 Speed (Overdrive) Gearbox
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  Q: What are the functions and components of an automatic transmission?

  A: The automatic transmission allows engine torque and power to be transmitted to the rear wheels within a narrow range of engine operating speeds. It uses a light fluid as the medium for the transmission of power and also works in the operation of various hydraulic control circuits and as a lubricant. The torque converter replaces the conventional clutch and has three functions: allowing the engine to idle with the vehicle at a standstill, allowing smooth shifting between ranges without closing the throttle, and multiplying engine torque as vehicle speed drops and throttle opening is increased. The torque converter consists of a metal case with three sets of blades: the torus or pump, the turbine, and the stator. Under low speed acceleration, the fluid flows through the torus and turbine, picking up speed and energy, and is redirected by the stator to allow the torus to turn faster than the turbine, resulting in higher engine power output and torque multiplication. A planetary gearbox is used to carry the power output of the turbine to the driveshaft, providing various reduction ratios. Servos and accumulators are used to engage the bands and clutches, with the servos being hydraulic pistons and cylinders and the accumulators cushioning their engagement. The hydraulic control system uses pressure from the main transmission oil pump, channeled through shift valves, to operate the servos. Governor pressure and modulator pressure, affected by vehicle speed and throttle position, respectively, control the operation of the shift valves and delay upshift points to optimize engine power output. An auxiliary circuit is used for downshifting, actuated by various means such as the throttle linkage or a solenoid. The transmission modulator also governs the line pressure to match the torque output of the engine for proper actuation of the clutches and bands.
• Exchange 5 Speed (Overdrive) Gearbox
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  Q: How to remove and install Manual Transmission Assembly?

  A: To remove and install E3D models, start by disconnecting the negative battery cable and raising the vehicle. Remove the exhaust system, cross brace, and heat shield. On the 325iX, also remove the transfer case. Disconnect the flexible coupling at the front of the driveshaft by holding the nuts on the front and removing the bolts from the rear. Remove the vibration damper if present. Loosen the threaded sleeve on the driveshaft and remove the center driveshaft mount. Move the driveshaft down at the center and pull it off the transmission output flange. Remove the shift selector rod and shift rod bracket. Remove the Clutch Slave Cylinder and the sending units for flywheel rotating speed and position. Detach the wiring connector for the backup light switch. Support the transmission and remove the crossmember holding it to the body. Remove the transmission flywheel housing bolts and separate the transmission from the engine. To install, align the input shaft and install the transmission. Coat the necessary parts with grease and torque the bolts to the appropriate specifications. Install the clutch slave cylinder and driveshaft center bearing. Torque the flexible coupling bolts and the driveshaft threaded sleeve. Finally, fill the transmission with the proper lubricant. For E36 models, start by disconnecting the negative battery cable and placing the transmission in neutral. Raise the vehicle and disconnect the oxygen sensor(s). Remove the exhaust system, cross brace bracket, and heat shields. Remove the driveshaft assembly and clutch slave cylinder. Detach the electrical connector from the back-up light switch. Support the engine and remove the transmission support cross member. Lower the engine and transmission slightly. Disconnect and remove the shift linkage and shift lever and bracket assembly. Inspect the area surrounding the transmission and remove the starter motor. Support the transmission and remove the transmission-to-engine mounting fasteners. Carefully slide the transmission away from the engine. To install, make sure the dowel pins are installed into the engine block. Coat the necessary parts with grease. Install the transmission and align the input shaft with the clutch disk. Slowly rotate the transmission output flange until the input shaft engages with the clutch disk splines. Carefully ease the transmission onto the engine and install the mounting fasteners. Torque the bolts to the appropriate specifications. Complete the assembly in reverse order, tightening the retainers and fasteners to the specified torque. Check the transmission fluid level and top off as necessary.
• Exchange 5 Speed (Overdrive) Gearbox
  23-00-1-220-371
  Q: What is the function of manual transmissions and clutches in internal combustion engines?

  A: Internal combustion engines produce torque within a specific speed range. Overhead valve pushrod engines typically achieve peak torque around 2500 rpm, often diminishing by 4500 rpm. Overhead camshaft engines generally have a higher, but narrower, torque peak. Manual transmissions and clutches adjust the relationship between engine RPM and wheel speed to ensure adequate power. The clutch gradually applies engine torque to the transmission input shaft due to mechanical slippage, allowing smooth starts from a stop. The transmission modifies the rotational speed ratio between the engine and the wheels using gears, with 4-speed or 5-speed versions being common. Lower gears ensure full engine power reaches the wheels during low-speed acceleration. The clutch driveplate, splined to the transmission input shaft, is coated on both sides with a material similar to brake lining that allows smooth slippage. The clutch cover, attached to the engine Flywheel, uses a diaphragm spring to engage the clutch and houses the Pressure Plate. When the clutch pedal is let go, the driven disc is pressed between the pressure plate and flywheel, making the disc rotate at the engine crankshaft's speed. The transmission features a main shaft that extends from the clutch to the driveshaft, segmented to allow different rotational speeds for its front and rear. Power in lower gears and reverse is transmitted via a countershaft. This countershaft's gears mesh with the mainshaft gears, transferring power between them. Several mainshaft gears either rotate freely or lock to the shaft. Shifting gears releases one and engages another, facilitated by internal dog clutches sliding between the gear's center and the shaft. Forward gears typically use synchronizers to align gear and shaft speeds before the dog clutches engage.