SERVICE MANUAL UPDATE UNIT REPAIR SECTION 7B1-M/T

Model and Year: 1988 LIGHT DUTY TRUCKS WITH HM-290 TRANSMISSION

This bulletin provides service manual updates for the HM-290 (refer Figure 1), 4 or 5-speed manual transmission Unit Repair Section that cover:

A. 2WD Rear Housing Removal B. Removing Clutch Fork Pivot Assembly C. Removing Countershaft Bearing Plug D. Removing and Installing Rear Housing Shift Shaft Bearing

The following changes should be made to the procedures in Section 7B1 of the 1988 C/K Light Duty Truck Unit Repair Manual.

NOTE: The changes that should be made to the 1988 C/K Truck HM-290 Unit Repair Section are IN CAPS.

A. The procedure for 2WD REAR HOUSING REMOVAL outlined on page 7Bl-34 should read:

7. Spiral roll pin (42) using J 36516 (Figure 20).

o Move the black depth locating tang for the spiral roll pin remover/installer out of the way, then drive down. o Put the black depth locating tang back in place with the rod going through it. o Turn J 36516 COUNTER-clockwise till it stops.

B. The procedure for REMOVING CLUTCH FORK PIVOT ASSEMBLY outlined on page 7B1-55 should read:

3. Clutch fork pivot assembly (219), using J 36510 and J 6125-lB (FIGURE 46).

o PUT AN ADDITIONAL NUT (WITH THREADS OF 3/8-16 IN.) INTO J 36510 AND THREAD J 6125-lB INTO NUT. o TIGHTEN BOTH NUTS. o SLIDE HAMMER OUT PIVOT.

C. The procedure for REMOVING COUNTERSHAFT BEARING PLUG outlined on page 7B1-55 should read:

5. Countershaft bearing plug (250) USING J 6125-lB (FIGURE 47).

o Remove staking. o DRILL HOLE THROUGH PLUG WITH A 5/16" DRILL BIT. o Tap using 3/8-16 tap. o Screw slide hammer into the plug. o Remove the plug.

D. The procedure for REMOVING REAR HOUSING SHIFT SHAFT BEARING outlined on page 7B1-61 should read:

2. Rear housing shift shaft bearing (309), using J 23907 with pilot bearing puller or J 36032 (FIGURE 66).

o Position PULLER LEGS BEHIND BEARING LIP. o Tighten. o Slide hammer out. o IF THE BEARING LIP BREAKS OFF, POSITION PULLER LEGS BEHIND THE INSIDE (OTHER END) BEARING LIP AND REPEAT PROCEDURE.

E. The procedure for INSTALLING REAR HOUSING SHIFT SHAFT BEARING outlined on page 7B1-62 should read:

2. Rear housing shift shaft bearing (309), using J 36506 AND J 36190 (FIGURE 69).

o INSTALL BEARING INTO BORE SO THAT THE WRITING ON BEARING LIP FACES DOWN. o Install flush.

All future manuals will include these revisions. Please record this information in your current manuals.

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.