Synchromesh Mechanism
BAULK RINGSTo change the baulk rings, follow the description entitled "To dismantle the gearbox", which specifies that the differential unit must be removed and the layshaft gearwheel must be removed to enable the primary chaincase to be removed.
To change the 1st and 2nd gear baulk rings, the output shaft must be removed from the gearbox, so that the gearwheels can be removed from the shaft.
TO REMOVE
To remove the baulk ring, remove the circlip retaining the baulk ring on the gearwheel.
TO FIT
First fit the guide rings for the springs and, for the 3rd and 4th gearwheels, the circlips for the guide rings. The gearwheels for 1st and 2nd gear have no circlips for the guide rings. Fit the spring with the long end towards the guide ring, and locate it so that there are 11 teeth between the spring ends. Locate the baulk ring so that the ends of the spring are between the teeth of the ring, and then fit the circlip.
(The spring for 1st gear synchromesh is softer and its free length is smaller than the others.)
NOTE: The guide rings on 3rd and 4th gearwheels fitted in production are peened in position in a special tool after the circlip has been fitted. The guide rings supplied as spares should not be peened.
1ST AND 2ND GEAR SYNCHROMESH UNIT
1. 2nd gearwheel
2. Guide ring
3. Spring for 2nd gear
4. Baulk ring
5. Circlip
6. Synchromesh hub
7. Synchromesh sleeve
8. Spring for 1st gear
9. 1st gearwheel
3RD GEAR SYNCHROMESH UNIT
1. Circlip
2. Baulk ring
3. Spring for 3rd gear
4. Guide ring
5. Circlip for guide ring
6. 3rd gearwheel
NEW SYNCHROMESH MECHANISM FOR 4-SPEED AND 5-SPEED GEARBOXES
The cone angles of the synchromesh sleeve and baulk ring have been altered from 6.67° to 6°. In addition, the baulk rings for 2nd and 3rd gears are coated with molybdenum. The gearwheels have asymmetrical tooth tip angles.
All new parts have been introduced on 5-speed gearboxes as from gearbox numbers 523814 and 480053. On 4-speed gearboxes, a new gearwheel for 2nd gear has been introduced as from gearbox No. 174284.
MARKING
To prevent mix-ups between new and old parts, the new baulk rings are provided with 6 pads (in pairs) on the outside diameter and the new sleeves have a turned step on the periphery. The groove can face either towards the front or towards the rear. The difference between old and new gearwheels is very clear, since the new gear-wheels have asymmetrically bevelled dog teeth.
NOTE: The new synchromesh sleeve (87 20 419) must always be matched with two baulk rings of new design (87 19 961 and 87 19 924), and vice versa.
1. Turned step (can face either towards the front or towards the rear)
2. Cone angle
3. Synchromesh sleeve
4. Baulk ring
5. Gearwheel
6. Symmetrical
7. Tip angle
8. Asymmetrical
BAULK RING 87 19 916 (MOLYBDENUM-COATED)
1. Pads (3 pairs) showing that the baulk ring has a cone angle of 6°
BAULK RING 87 19 924
1. Pads (3 pairs) indicate a cone angle of 6°