SHIFT LEVER SHAKE AND/OR NOISE IN 2ND GEAR (SERV. PROCEDURE)

Subject: SHIFT LEVER SHAKE AND/OR NOISE IN 2ND GEAR

Model and Year: 1991-93 C/K, P TRUCKS WITH NV4500 5-SPEED MANUAL TRANSMISSION

Some owners of 1991-93 C/K, P trucks equipped with a NV4500 (RPO MT8) 5-speed manual transmission may comment that their vehicle experiences shift lever shake and/or transmission noise when the shift lever is in 2nd gear as labeled on the shift knob.

This condition may be caused by wobble in the shift sleeve (94) which results in noise as the sleeve (94) contacts the shift fork (1 1) and/or lever shake if the shift sleeve (94) wobble is great enough.

This condition may be corrected by replacing the three/four synchronizer assembly (91-94), the 3rd speed gear (87/89), the main drive clutch gear (95) and the shift cover assembly (8). The synchronizer and gears have revised teeth for improved mating and the cover features a revised detent in the 3-4 shift rail to reduce lever shake.

VEHICLES INVOLVED:

Some 1991-93 C/K, P trucks equipped with a NV4500 5 speed manual transmission built prior to the following VIN breakpoints:

Detroit (3) P3100000 Ft. Wayne (Z) PZ100000 Janesville (J) 3500 HD PJ100008 Crew Cab PJ303097 Oshawa (1) P1119152 Pontiac (E) PE111276

SERVICE PROCEDURE:

Refer to the appropriate Unit Repair Manual (Section 7B2, New Venture Gear 4500 Manual Transmission) for Unit Disassembly and Assembly and Mainshaft Disassembly and Assembly. Follow the procedures listed to:

- Remove the mainshaft assembly (57-94) from the transmission. - Remove the three/four synchronizer assembly (91-94) from the mainshaft. - Remove the third speed gear (87/89) from the mainshaft. - Install the new third speed gear (87/89) - Install the new three/four synchronizer assembly (91-94)

IMPORTANT: A new synchronizer assembly can change mainshaft endplay. Endplay should be checked and must be .002"-.006". Change mainshaft bearing shims (141) as required.

- Install the new main drive clutch gear (95) to the main drive gear (98).

- Install a new shift cover assembly (8). This new cover requires the installation of a new vent tube (52) and new reverse fbrk pads (1 2). Transfer the shift stub lever assembly including the boot seaj (1 -4), and back-up switch and gasket (50-15) from the previous cover.

IMPORTANT: The new vent tube must be installed facing forward pointing up 15 to 35 degrees from horizontal. Refer to the existing vent tube for correct position.

The following parts are not reusable and must be replaced upon reassembly: - Mainshaft nut (28 or 32) - Rear retainer (extension) bolts (33) - Drive gear bearing retainer bolts (113) - Mainshaft bearing retainer plate bolts (128)

The following fastener tightening specifications update the 1991 and 1992 Unit Repair Manual and should be used:

- Countershaft retainer plate-to-case bolts 35 N.m (26 lbs. ft.) - Mainshaft retainer plate-to-case bolts 35 N.m (26 lbs. ft.) - Main drive gear retainer-to-case bolts 31 N.m (23 lbs. ft.) - Shift over-to-case bolts 28 N.m (21 lbs. ft.) - Rear (extension) oil retainer-to-case bolts 54 N.m (40 lbs. ft.) - Vibration damper mounting nut (4WD) 441 N.m (325 lbs. ft.) - Yoke assembly mounting nut (2WD) 441 N.m (325 lbs. ft.)

Sealants which should be used for reassembly are noted below:

- P/N 1052942 Anaerobic sealant - Shift cover-to-case flange - Rear extension housing-to-case flange - Main drive gear bearing retainer-to-case flange

- P/N 12346004 Pipe sealant with TEFLON - Drain and fill plugs

- Main drive gear bearing retainer bolts (circle the retainer bolt holes with sealant)

This transmission requires a special synthetic IMPORTANT: lubricant P/N 12345871. Do NOT substitute any other lubricant as internal transmission damage may occur.

SERVICE PARTS INFORMATION

Part Quantity Number Description Required -------- ------------ --------

12542865 Synchronizer, 3rd and 4th 1 12542867 Gear, 3rd 1 12542868 Gear, trans drive clutch 1 12542869 Cover, trans shift lever 1 15581915 Pipe, trans vent 1 15635276 Pad, trans fork end 2 15635277 Pad, trans fork center 1 15535364 Nut, mainshaft, Cl,2,3 w/o 1 propshaft mounted park brake 15635327 Nut, mainshaft, Kl,2,3 1 15635261 Bolt, drive gear retainer 4 15635285 Bolt, rear retainer 8 12542559 Bolt, bearing retainer plate 4 See Prts Bk Shim, trans mainshaft brg As needed Grp 4.406 12345871 Fluid, manual trans (1 gallon) 1 12346004 Sealant, pipe w/TEFLON As needed 1052942 Sealant, Loctite Gasket Maker As needed

Parts are currently available from GMSPO.

WARRANTY INFORMATION

Labor Operation: T7586

Labor Time (hrs.): C K P 3.5 4.3 4.1

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.