KNOCKING OR TAPPING NOISE IN ALL GEARS-W/CLUTCH OUT

Models Affected: 1989 HM-282/5TM40 6000, SUNBIRD, GRAND AM AND GRAND PRIX MODELS

This bulletin cancels and replaces bulletin 89-7-39 issued 7/89. This bulletin has been revised to add additional information under "Bulletin Covers", "Date Of Production Change" (Chart Added), and "Service Procedure" (ist paragraph).

BULLETIN COVERS:

Some HM-282/HYDRA-MATIC 5TM40 Transaxles built between approximately November 1, 1988, and April 7, 1989, may exhibit a knocking or tapping noise in all gears and neutral with the clutch pedal out. This condition is termed Gear Noise.

PROPER DIAGNOSIS IS IMPORTANT: Do not confuse this Gear Noise with Clutch Rattle or Neutral Gear Rattle. A knocking or tapping noise which is only heard in neutral with the clutch pedal out is clutch rattle or neutral gear rattle. Reference Pontiac Service Bulletin 88-7-40 issued 10/88.

DATE OF PRODUCTION CHANGE:

A vehicle equipped with a HM-282/HYDRA-MATIC 5TM40 built between approximately November 1, 1988, and April 7, 1989, may exhibit the gear noise condition described above. Refer to the chart below for specific model breakpoint information:

Model Beginning Serial No.* Ending Serial No.* ----- ---------------------- ------------------- 9XAX 10 4471 9XBX 10 9920 9XCX 6 1047

9XFX 5611 8830 9XMX 879 5002 9XNX 4344 22157

9XSX 3767 8380 9XXX 1139 4457 9XLX 2639 5611

*These serial numbers are found on the transmission Bar Code Label (see figure 1) . Any transmission model built between and including the beginning and ending serial numbers shown may exhibit Gear Noise.

SERVICE PROCEDURE: (Figures 2, 3, 4, 5)

If your diagnosis indicates that the transaxle exhibits a knocking or tapping in all gear ranges with the clutch pedal out and it has a bar code serial number shown in the chart above:

Inspect the gear cluster, input gear (17). If it does not have a groove as indicated in Figure 2, install the part described in Service Parts Information.

Inspect the reverse idler gear (103) and reverse gear/5th synchronizer assembly (25) for chipped or deformed teeth (refer to Figure 5). To check for deformity, compare the angle and position of the teeth with a known good gear. If either component exhibits a chipped or deformed condition, replace both parts as described in Service Parts Information.

Inspect the shift cable, at the center shift console, for binding where it enters the sheath. (The shift cable is the thicker of the two shift control cables.) A bent cable could result in binding, difficult shifting, and/or inaccurate shift detent feel, especially when shifting into reverse. Replace the cable if it is bent or kinked.

SERVICE PARTS INFORMATION:

Part Number Description ----------- ----------- 8672955 Cluster, Input Gear (Non-Turbo)(17) 8672956 Cluster, Input Gear (Turbo)(17) 8672179 Gear, Reverse Output/5th Synchronizer Asm (25) 14080558 Gear, Reverse Idler (103) 8672918 Package, Overhaul

The overhaul package must be installed when replacing any of the above parts.

Parts are currently available from GMSPO.

SERVICE MANUAL REFERENCE:

Refer to the HM-282/HYDRA-MATIC 5TM40 Unit Repair section of your Service Manual.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.