HT4100 MAIN BEARING USAGE UPDATED REVISIONS LISTED

VEHICLES AFFECTED: ALL WITH HT4100 ENGINES

With the introduction of the 1987 model year, minor revisions have been incorporated in the HT4100 main bearings which dictated the following revisions to ctshp hoaring usage chart from pages 1 and 2 of the Service Bulletin 84-6-218.

SERVICE BEARING EDGE PART PART APPLICATION POSITION COLOUR NUMBER* NUMBER** STATUS ----------- -------- ------ ------ ------ ------

ORIGINAL #1 NONE 18006622 18009086 OBSOLETED PRODUCTION BY 180123--16

2ND DESIGN #1 PURPLE 18012275 18012316 OBSOLETED PRODUCTION BY 18014329

3RD DESIGN #1 RED 18014079 18014329 PRODUCTION

SERVICE ONLY #1 BLUE 18012276 18012317 OBSOLETED O.S. (2ND DESIGN)' BY 18014307

SERVICE ONLY #1 BLUE 18014306 18014307 O.S. (3RD DESIGN)

ORIGINAL #2 AND #4 NONE 18006622 18009086 OBSOLETED PRODUCTION BY 18013442

2ND DESIGN #2 AND #4 NONE 18013016 18013442 PRODUCTION

ORIGINAL #3 NONE NONE 18009088 OBSOLETED PRODUCTION BY 3634715

2ND DESIGN #3 1640033 3634715 PRODUCTION (1987 1/2)

3RD DESIGN #5 GREEN 18013607 18013789 USE IN PRODUCTION (1987) TRANSVERSE ENGINES ONLY

SERVICE ONLY #5 BLACK 18013608 18013790 USE IN O.S. (3RD TRANSVERSE DESIGN) ENGINES ONLY

* PART NUMBER is number stamped on back of bearing shell. Use this number for identification.

** SERVICE NUMBER is number addigned to the part and printed on the box. Use this number for ordering parts.

***Special Note: The clearance checks referred to in Bulletin 84-6-218 should be .0508 mm (.002 inch) rather than .1016 mm (.004 inch) for number 1 and 5 main bearings.

MAIN BEARING #3 (THRUST MAIN)

While no significant revisions have been incorporated in this bearing, a new supplier has been selected which has necessitated a new part number. This change is scheduled to occur sometime during the 1987 model year, however, establishing a breakpoint is not required since both parts can be used interchangeably.

MAIN BEARING #5

A revised #5 main bearing entered production at the start-of-production 1987. This 3rd design bearing can be identified by a green edge colour and lack of a 2nd oil groove at the edge of the bearing facing the rear main seal. The purpose of this 2nd groove is to channel oil away from the rear main seal. Research at Cadillac has shown that the one piece rear main seal on tranverse HT4100 en,gines does not require this feature. The 2nd design parts should be used on longitudinal engines and the newer 3rd design parts restricted to transverse applications only.

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.