Adjusting Drive Set, Differential and Differential Lock
Adjusting drive set - GT2
Tools
Sequence of adjustment operations
If the pinion shaft and crown wheel have to be adjusted, it is best to follow the sequence below in the interest of rational working:
1. Determine the total disc thickness S1 + S2.
2. Determine disc thickness S4 and S5.
3. Determine disc thickness S3.
4. Divide the total disc thickness into S1 and S2.
5. Check the circumferential backlash and set, if necessary.
Note! The aim of the adjustment operations is to regain the position of maximum smooth running which was determined in production on a testing machine.
Determining disc thickness S4 and S5
1. Disassemble the transmission.
Note! The input shaft need not be disassembled for this setting.
2. Insert adjusting shim S3 -A- with a thickness of 1 mm.
3. If the tensioning plate has not been disassembled, install it with the input shaft.
Tightening torque: 25 Nm (19 ft. lbs.)
4. Measure the play at the four-point bearing. To do so, fit the dial gauge with the special tool dial gauge holder VW 387. Press the outer bearing race forwards as far as possible and set the dial gauge to 0.
5. Press the outer bearing race backwards as far as possible and read the play off the dial gauge.
Example: 1.00 mm
Note! The measured play plus the specified bearing pretension of 0 to 0.07 mm indicate the thickness of disc S4.
Example: 1.00 mm + 0.05 mm = 1.05 mm = S4
6. Experience shows that the thickness of disc S5 corresponds to the thickness of disc S4.
Example: S4 = S5 = 1.05 mm
7. Insert output shaft -A- with adjusting shim S5 -B- and adjusting shim S4 -C- into tensioning plate -F-.
8. Push 4th gear fixed wheel -D- onto output shaft. The large collar faces the tensioning plate.
9. Push on oil pump drive wheel -E-.
10. Insert the preselected adjusting shim S3 into the transmission housing and install the tensioning plates with the shafts.
Determining disc thickness S3
1. Push fixed wheel for 3rd gear on to the output shaft. The narrow collar faces the tensioning plate.
2. Shift into 4th gear.
3. Block the input shaft with special tool retaining device 9253.
4. Push special tool assembly sleeve 9263 -A- and discs (Part No. 950.302.296.03) -B- on to the output shaft.
5. Screw collar nut on to the output shaft.
Tightening torque: 300 Nm (222 ft. lbs.)
6. Set the setting collar on special tool measuring mandrel VW 385/1 to the dimension a (approximately 65 mm).
7. Complete the measuring mandrel as shown in the illustration.
8. Read off the installation dimension E from the crown wheel.
1 Installation dimension E
2 Backlash F
3 Matching number
Example: E = 70.20 mm
9. Set the installation dimension E on special tool universal master gauge VW 385/30 and set the dial gauge to 0 with 2 mm pretension.
10. Place special tool adjusting shim 9281 on the pinion head of the output shaft.
11. Insert the measuring mandrel as shown in the illustration.
12. Place the side transmission cover in position without an Wring and pull downwards with 4 screws. Do not knock.
Tightening torque: 25 Nm (19 ft. lbs.)
13. Press tapered roller bearing with the centring screw over the spindle into the bearing shells. It should just be possible to turn the measuring mandrel by hand.
14. Turn the measuring mandrel carefully back and forth until the reversing point on the dial gauge is reached. At this point, the dial gauge extension is positioned exactly at right angles to the front face of the pinion head.
15. Read off the deviation from the specified adjusting value E. If the deviation is greater than 0.04 mm, a correction must be carried out.
Example: 0.10 mm
Note! So in the example, the actual value of the adjusting dimension E would not be 70.20 but rather 70.30 mm.
16. In order to achieve the required adjusting dimension E, the adjusting shim S3 must be adjusted by the measured value.
Example: new disc thickness S3 = 0.90 mm
17. In order to correct the altered disc S3, disc S4 must be altered in the opposite direction by the determined value.
Example: S4 = 1.15 mm (increase by 0.10 mm)
18. As the thickness of disc S4 is identical to the thickness of disc S5, disc S5 must be altered by the same value as disc S4.
Example: S5 = S4 = 1.15 mm
19. When the discs S3, S4 and S5 have been corrected appropriately and inserted, the adjusting dimension E should be checked again.
Determining disc thickness S1 and S2
Note! The crown wheel must be adjusted again if the transmission housing, the side cover, the tapered roller bearing for the differential, the differential housing or the drive set are replaced.
Determining total disc thickness S1 + S2
1. Remove the tensioning plate with the input and output shafts.
2. Insert 2 discs S1 and S2 with a thickness of 2.5 mm each into the differential and mount the tapered roller bearing.
Note! The chamfers of the adjusting shims point towards the housing.
3. Insert the differential into the housing and turn it several times.
4. Mount the side transmission cover without a shaft seal and screw in all screws.
Tightening torque: 25 Nm (19 ft. lbs.)
5. Fit special tool adjustment device VW 521/4 opposite the crown wheel side (S2 side) into the differential.
6. Place the special tool end plate VW 385/17 -B- on to the differential.
7. Fasten special tool dial gauge holder VW 387 on the housing with the dial gauge and the special tool dial gauge extension VW 385/56 -A-.
8. Set dial gauge with 2 mm pretension to 0.
9. Press the differential upwards as far as possible with special tool adjustment device VW 521/4.
10. Read off the play on the dial gauge.
Example: 0.75 mm
Note! The differential must not be turned during the measurement, as otherwise the measurement will be falsified.
11. The total thickness of discs S1 and S2 is calculated from the total of the already inserted discs plus the measured value plus the specified bearing pretension of the tapered roller bearing.
Example: 5.00 mm + 0.75 mm + 0.40 mm = 6.15 mm = S1 + S2
Note! The pretension of the tapered roller bearing in this transmission is always 0.40 mm.
Dividing the total disc thickness into S1 and S2
Note! In order to gain as precise a setting of the backlash as possible at this point, the adjusting shim S1 must be 1.4 mm thicker than adjusting shim S2.
Example: disc thickness S1 = 6.15 mm /2 - 0.7 mm = 2.375 mm
Example: disc thickness S2 = 6.15 mm /2 + 0.7 mm = 3.775 mm
Note! As the adjusting shims are available in thicknesses from 1.5 to 2.8 mm in increments of 0.05 mm, the calculated result must be rounded off. However, the total of the disc thicknesses S1 + S2 must not be changed. To determine the thickness, measure the adjusting shims at several places with a micrometer. The discs should also be checked for burrs and damage.
Example: disc thickness S1 = 2.375 mm; inserted adjusting shim = 2.35 mm
Example: disc thickness S2 = 3.775 mm; inserted adjusting shim = 3.80 mm
Example: total of both inserted discs = 2.35 + 3.80 = 6.15
1. Remove the differential and pull off both tapered roller bearings.
2. Insert the calculated adjusting shims S1 and S2.
Checking the circumferential backlash and setting, if necessary
1. Read off the backlash at the crown wheel.
1 Installation dimension E
2 Backlash F
3 Matching number
2. Mount the input and output shafts with tensioning plate and adjusting shims.
Tightening torque: 25 Nm (19 ft. lbs.)
3. Mount the gear set and the gear housing. Then assemble front gear set go to Rep. Gr. 34 35 37; Disassembling and assembling transmission.
4. Screw collar nut on to the output shaft.
Tightening torque: 300 Nm (222 ft. lbs.)
5. Install the differential and mount the side transmission cover with all the screws.
Tightening torque: 25 Nm (19 ft. lbs.)
Note! Always make sure a certain amount of backlash is present when tightening the screws. The drive pinion must not jam under any circumstances.
6. Screw in special tool gauge plunger VW 388 with special tool adjustment device VW 521/4 and set the lever length to 91 mm -a-.
7. Insert special tool adjustment device VW 521/4 into the differential with special tool bushing 9145 and clamp tight.
8. Turn the differential several times in both directions so that the tapered roller bearings can settle.
9. Mount the special tool dial gauge holder VW 387 with the dial gauge in such a way that a right angle is formed between the dial gauge axis and the special tool gauge plunger VW 388.
10. Install special tool retaining device 9562.
11. Turn the crown wheel as far as it will go via the clamping screw of the special tool adjustment device VW 521/4 and set the dial gauge to zero.
12. Turn the crown wheel back and read off the circumferential backlash.
13. This measurement should be performed a further three times. The crown wheel must be turned 90° before every measurement. The difference between the four measurements must not exceed 0.03 mm. Moreover, none of the measurements may deviate by more than 0.04 mm from the circumferential backlash noted on the crown wheel. If any of the specified dimensions is not observed, the adjusting shims S1 and S2 must be replaced again.
Note! The total disc thickness S1 + S2 must not be changed.