SEAL 9D7984 - Caterpillar

Commercial Engines: 3406B 3406CTruck Engines: 3406B 3406CMachine Engines: 3406B 3406CIntroduction
Most 3406B and 3406C engines were produced with a cylinder block that had a 19 bolt hole pattern for the flywheel housing. The 0R-3751 and the 0R-3752 are remanufactured long blocks that are intended for the repair of the 3406B and 3406C engines. The long block is assembled with cylinder blocks that have either a 19 bolt hole pattern or a 24 bolt hole pattern for the flywheel housing. A flywheel housing with 19 bolt holes or 24 bolt holes will work with either long block if the correct gasket is used between the flywheel housing and the cylinder block. Flywheel Housing
The following table indicates the correct gasket to use for all combinations of flywheel housings and long blocks:
Table 1
Cylinder Block
Bolt Hole Pattern     Flywheel Housing
Bolt Hole Pattern     Gasket    
19     19     159-3021    
19     24     159-3021    
24     19     159-3021    
24     24     155-5619    
Illustration 1 g00763088
Flywheel Housing with the 24 Bolt Hole Pattern (1) Bolt HoleBolt hole (1) needs to be plugged if you are using a flywheel housing with a 24 bolt hole pattern on a long block with a 19 bolt hole pattern. This will prevent oil from leaking and debris from entering the engine. The plug should be flush with the spot face on the side of the flywheel housing that faces the transmission assembly. Use the following steps in order to install the plug:
Tap bolt hole (1) for a 0.25 inch NPTF plug.
Install a 7H-3171 Pipe Plug in bolt hole (1) on the flywheel housing.
Verify that the plug is flush with the spot face.Front Cover
Illustration 2 g00764455
Left Side View of the 3406B and 3406C Engines (1) Cylinder Head (2) 1W-2488 Cover (3) Front Housing (4) Cylinder BlockCertain applications of the 3406B and 3406C engines require cover (2) to be installed over the opening for the air compressor mount that is located on the upper left rear corner of the 1W-1471 Front Plate . The 1W-1471 Front Plate is part of the front housing. The following table shows the part number for cover (2) and associated parts that should be used to seal the opening for the air compressor mount:
Table 2
Qty     Part Number     Part Description    
1     1W-2488     Cover    
1     100-7432     Gasket    
3     1F-7958     Full Nut    
1     2B-2006     Bolt    
1     9S-1366     Bolt