M/T - Knocking or Rattle Noise from Front of Vehicle: Overview

BULLETIN NO.: 98-T-24A

ISSUE DATE: September, 1998

GROUP/SEQ. NO.: Transaxle-03

CORPORATION NO.: 887301R

SUBJECT:
Knocking or Rattle Noise from Front of Vehicle During Deceleration (400 RPM and Lower) (Replace Clutch Disc, Clutch Cover, and Machine a Chamfer into Flywheel)

Due to changes in the service procedure, this bulletin supercedes 98-T-24, which should be discarded.

MODELS AFFECTED:

1996-1998 Saturn vehicles built before and including VIN WZ3O5219 equipped with MP2 or MP3 manual transaxles

CONDITION:

Some customers may comment on a knocking or rattle type noise coming from the manual transaxle during moderate to heavy deceleration in any gear. The complaint is most noticeable when lifting off the throttle and decelerating from 4000 RPM and lower.

Note:
If the gear rattle experienced does not match the symptoms as described above or the noise is not considered to be normal gear "mesh" noise, refer to diagnostics in the appropriate model year Manual Transaxle Service Manual. In these cases the long travel damper clutch disc will have no effect on eliminating or reducing these complaints.

CAUSE:

The gear rattle is caused by insufficient dampening of engine pulsations by the clutch disc dampening springs. These pulsations allow the unloaded transaxle drive gears to knock against the driven gears. This knocking creates an audible "gear rattle."

CORRECTION

To address this concern, a long travel damper clutch disc, (P/N 21120564), has been released. The new clutch disc is larger than the current clutch disc (P/N 21120453). In order to allow clearance for the long travel damper clutch disc, the inner diameter of the clutch cover has been increased and the inside edge of the current flywheel must be chamfered. The part number of the new clutch cover is 21120582. When servicing a vehicle where it is necessary to replace the current clutch disc with the new long travel damper clutch disc, it is also necessary to machine a chamfer into the current flywheel and replace the original clutch cover (P/N 21120455) with new clutch cover (P/N 21120582).

IMPORTANT:
Prior to performing the following service procedure, check the vehicle service history to determine whether the flywheel has already been resurfaced. Due to clearance issues, a resurfaced flywheel and latest design disc are not compatible. The minimum flywheel thickness is 28.25 mm (1.11 in). Using a micrometer, measure flywheel thickness in three places around the circumference of flywheel. All measurements must be made at the same distance in from the edge of flywheel and at equal distances from each other. If the flywheel has been resurfaced previously or is less than 28.25 mm (1.11 in) in thickness and the clutch disc is being replaced with the long travel damper disc (P/N 21120564), it is necessary to replace the flywheel with chamfered flywheel (P/N 21120535).