GEAR RATTLE/REVERSE BLOCKOUT NEW SYNCHRONIZER/CLUTCH DISC

Some 1982 and early production 1983 "S" trucks equipped with the 77.5mm Isuzu 4-speed manual transmission may exhibit one or both of the following conditions:

* Gear rattle while in gear, in neutral or both.

* Reverse blockout.

These symptoms may be eliminated as described in the following paragraphs, by using the parts as listed.

Gear Rattle - In Gear

In vehicles equipped with the 2.8L V6, RPO LR2 (VIN Code B), the 1st - 2nd and 3rd - 4th synchronizer assemblies should be replaced with the new design. On vehicles equipped with the four cylinder RPO LR1 (VIN Code A), the synchronizer assemblies should be replaced along with a new design clutch disc. The synchronizer sleeve and hub parts have a new ball and spring anti-lash feature. The clutch disc has a new damper spring. Gear rattle - in gear corrected after transmission serial number L4 80896 and V6 80888.

Gear Rattle - In Neutral

In vehicles equipped with four cylinder engines, the new clutch disc should be installed.

Reverse Blockout

If it is difficult to shift the transmission into reverse, the reverse idler, the reverse main shaft and the reverse counter gears should be replaced as a set. The gear tooth chamfer shape has been revised and these gears must be used together in order for the repair to work.

Reverse blockout was corrected in transmission built after transmission serial numbers L4 79925 and V6 79870.

PARTS LIST

Item P/N Usage

1st - 2nd Synchronizer Assembly 94115609 In-gear rattle, 3rd - 4th Synchronizer Assembly 94115608 LR1 and LR2

Clutch Driven Plate 94114746 In-gear rattle & neutral rat- Cover and Pressure Plate Assembly 94114745 tle, LR1 only

Reverse Idler Gear 94115371

Reverse Main Shaft Gear 94115373 Reverse block- out Reverse Counter Gear 94115374

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.