If a rattle noise is heard on a vehicle with a manual transmission, attention should be paid to the Dual Mass Flywheel (DMF).
In the case of customer complaints, follow the steps below.
A. Measure the DMF Radial Free-Play:
The DMF should be mounted on the crankshaft during the measurement. (For the measurement you will need a torque wrench.)
1. Impose a torque of 6 Nm (4.4 lbf.-ft.) on one of the bolts that holds the clutch and DMF together.
• The secondary side of the DMF will now turn in the same direction as the applied torque.
2. Draw a line over both the primary and secondary side of the DMF.
3. Now impose a 6 Nm (4.4 lbf.-ft.) torque in the opposite direction than before.
• The secondary side of the DMF will now turn in the same direction as the applied torque.
4. Draw a line on the primary sides of the DMF in alignment with the line that you previously drew on the secondary side of the DMF.
5. Measure the distance between the two lines on the primary side of the DMF.
6. If the distance is below 35 mm (1-3/8”), the radial play of the DMF is OK.
B. Measure the DMF Axial Free-Play:
The DMF should be demounted from the crankshaft and placed on an even surface during the measurement. (For the measurement you need a dial indicator.)
1. Use a dial indicator and place it as shown in Fig. 1. The DMF should be in equal balance when the dial indicator is put in place.
2. Apply a force of approximately 100 N (approx. 10 kg mass or 22.5 lbf.) on pin (A) at the opposite side of the dial indicator.
3. Read the distance of the axial free-play on the dial indicator.
4. Now turn the DMF one-third of a revolution and do the whole procedure from the beginning (from point 1) and apply the force on pin B.
5. Repeat the procedure for pin C.
6. If the largest distance from the three cases is below 2 mm (0.078”), the axial play of the DMF is OK.
Replace the DMF if radial or axial free-play are outside specification, or if the noise is still present.
Courtesy of Mitchell 1.
