Gearbox assembly (BMW 3 Series E21)

Replacing secondary and intermediate shaft bearings

Heat the gearbox housing on a heating plate to a temperature of approximately 80°C and press the bearings out of the seats.

New bearings are pressed in with the markings facing the rear of the gearbox.

Assembly

During the gearbox assembly process, it is necessary to lubricate the parts with gearbox oil as they are installed.

Clamp the secondary shaft in a vice with soft pads.

Install the needle bearing, 2nd gear pinion and synchronizer locking ring on the secondary shaft belt. Measure the clearance between the end face of the locking ring and the end face of the gear ring. If it is less than 0.8 mm, replace the synchronizer locking ring.



Install the hub of the sliding clutch of the synchronizer of the 1st and 2nd gears and the second locking ring of the synchronizer on the secondary shaft.



Heat the 1st gear bushing on a heating plate to a temperature of 100-120°C; in this case, it is recommended to control the temperature with thermochromic pencils (for example, manufactured by Faber Castell).



Press the needle bearing, 1st gear and bushing onto the secondary shaft (make sure it is heated to the specified temperature first) using a mandrel and a hammer.

Install a 0.10 mm thick adjusting ring on the secondary shaft, and then place the inner ring of the roller bearing installed in the intermediate housing on the shaft, using a mandrel if necessary.



Determine the axial free play of the reverse gear, which corresponds to the standard if the distance "A" (see photo) between the end face of the bearing race and the flange of the secondary shaft is equal to the height "B" of the hub of the 5th gear and reverse synchronizer clutch assembled with the bushing. If necessary, achieve equality of dimensions by installing adjusting rings under the hub bush of the 5th gear and reverse synchronizer clutch.





Remove the secondary shaft from the vice, turn it over and clamp it in the vice again.

Install the needle bearing on the secondary shaft (with plastic separator) gears of the third gear, gear of the third gear, synchronizer locking ring, hub of the sliding clutch of the synchronizer of the third and fourth gears, directing the flange towards the gear of the fourth gear, adjusting ring and locking ring. By selecting the thickness of the adjusting ring, ensure a tight fit of the parts.

Install the synchronizer locking ring for III and IV gears on the secondary shaft and press the bearing onto the end of the shaft.

Connect the primary shaft to the secondary shaft.

Position the intermediate shaft opposite the primary and secondary shaft assemblies and insert the shafts into the intermediate case.



Place the gearbox in a vertical position with the gear blocks facing down, supporting the shafts with a pipe resting on a wooden block.



Heat the reverse gear bushing to 100-120°C.

Install the adjusting rings of the required thickness (see above), then press on the reverse gear bushing using the 23 1 160 mandrel.

Install the needle bearing (with plastic separator) and the reverse gear.

Place the gearbox in a horizontal position.

Connect the hub and the sliding sleeve of the synchronizer of the 5th gear and reverse gear.

Insert the ball of the 5th gear and reverse gear fork rod retainer into the intermediate case socket.

Connect the rod with the 5th gear and reverse gear engagement fork together with the hub and synchronizer clutch and install them in the gearbox housing.

While holding the rod, put the pin of the 5th gear and reverse gear fork into place, move the rod, the fork with the hub and the 5th gear and reverse gear synchronizer clutch, and then move the hub of the synchronizer clutch to the stop.

Bring the rods together with the shift forks of III and IV, I and II gears closer to each other.

Install the ball of the fork rod retainer for the 5th gear and reverse gear and the 3rd and 4th gear shift into the socket of the intermediate housing, then put the ball of the fork rod retainer for the 3rd and 4th gear shift into place.

Install the ball of the 1st and 2nd, 3rd and 4th gear fork rod lock into the intermediate housing socket, then put the 1st and 2nd gear fork rod lock hinge back in place and install this rod. If necessary, remove the cover from the 1st and 2nd gear fork rod lock socket. After installing the rod, be sure to put the lock cover back in place.



Install the gear selector rod assembly with the leash and the intermediate rod.

Install the intermediate lever with the rounded part down and screw the bolt-axle into the intermediate housing, having first applied a special adhesive such as Loctite to the threads.

Install the intermediate rod support by tightening the mounting screw.

Secure the gear selector lever and the III and IV gear shift fork with pins.

Place the gearbox in a vertical position with the gear blocks facing down.

If necessary, heat the 5th gear bushing to a temperature of 100–120°C.

Install jig 23 1 450 on one of the guide projections of the hub of the 5th gear and reverse synchronizer clutch and press the 5th gear sleeve onto the secondary shaft using mandrel 23 1 040 and a hammer, then remove the jig.



Install the 5th gear and reverse gear synchronizer locking ring.

Press the 5th gear and needle bearing onto the secondary shaft.

Press the 5th gear onto the intermediate shaft using mandrel 23 1 040.

Press the 5th gear sleeve onto the intermediate shaft, after heating it up first.

Install the adjusting rings on the 5th gear sleeve and press the inner bearing ring onto the end of the intermediate shaft.



Insert a pin into the hole at the end of the intermediate shaft. Check if the parts at the end of the intermediate shaft are tightly seated. If not, replace the adjusting rings with thicker rings.

Install a spacer ring on the V-gear gear of the secondary shaft and press the speedometer drive pinion onto the shaft, having first heated it.

Press the bearing onto the rear end of the intermediate weft shaft with the larger diameter of the separator facing away from the 5th gear.

Place the gearbox in a horizontal position.

Move the fork rod for engaging 1st and 2nd gears to the position corresponding to engaging 2nd gear; in this case, lift the leash to a position in which the orientation of the end of the rod would ensure the installation of the locking cracker of the rods of the 1st and 2nd gear shift forks and the engagement of 5th gear and reverse.



Install the secondary shaft rear bearing cover (without putting a gasket), by applying a sealant such as Loctite 573 to the mating surfaces.

Insert the 1st and 2nd gear shift fork rod into the rear gearbox cover. Remove the inspection hole cover and make sure the locking cracker is in the correct position, then replace the cover.

Tighten the left upper bolt securing the rear cover to the intermediate crankcase.

Install the pin into the hole in the 1st and 2nd gear shift fork.

Insert the two rear cover dowel pins into the intermediate case holes.

Heat the rear cover and press the secondary shaft rear bearing into the socket with the inscription from its cover using the 7026-1 lining amendment 7026; in this case, to ensure a secure fit of the bearing, hit the mandrel several times with a hammer.



Turn the gearbox over with the secondary shaft facing up.

Install the secondary shaft rear bearing cover gasket and measure the bearing recession relative to the rear cover plane with a depth gauge, and then the height of the bearing cover seating belt. The difference in measurement results determines the thickness of the adjusting ring to be installed.





Install an adjusting ring on the secondary shaft rear bearing to ensure there is virtually no gap between the bearing and the cover (preload should not exceed 10/100).

Install the secondary shaft rear bearing cover by tightening the mounting bolts; in this case, the short bolt should be inserted into the upper right hole of the cover.

Press the flange onto the secondary shaft splines using the 7026 mandrel and thrust spacer (as the latter, you can use an old thrust bushing.)

Tighten the secondary shaft flange nut, installing a protective sleeve on its end. When performing this operation, use the 6039 locking tool and a 30 mm sleeve.

Press the front bearing of the intermediate shaft into the socket of the gearbox housing, having first put grease into the bearing; in this case, direct the larger diameter of the bearing generator towards the clutch. Connect the gearbox housing to the intermediate housing, having previously applied a sealant such as Loctite 573 to the mating surfaces.

Install the intermediate case mounting bolts to the gearbox housing and push the two intermediate case mounting pins into the gearbox housing hole.

Tighten the intermediate case to gearbox case mounting bolts.

Install the locking sleeve, spring and gear selector rod retainer cover horizontally.

Press the front bearing of the primary shaft into the socket of the gearbox housing, having preheated it.

Lift the input shaft several times to allow the bearing to self-align.

Place the adjusting and retaining rings on the input shaft.

Measure the distance between the end face of the input shaft front bearing and the support surface of the front cover. Compare the measurement result with the protrusion of the bearing outer ring when it is installed in the front cover.



Select adjustment rings that are thick enough to provide a tight fit.

Press on the outer race of the front bearing of the primary shaft, install the adjusting rings and the front cover, applying a sealant such as Curil K2 to the mating surfaces.



Screw in the reverse light switch.