HEAD 1598905 - Caterpillar

3406B/C (8TC, 4MG, 3ZJ, 5KJ, 2EK, 4CK, 5YG) Truck EnginesThe changes to the timing advance drive groups are divided into lists for the mechanical engines and the electronic engines. The changes are listed in chronological engine serial number order.
Mechanical
4MG3600
Released new style timing advance with a cone shaped cover. When compared with the former advance, this advance provides increased advance capacity (up to 12.5 degrees). The new drive group part numbers are 4W8334, 4W8333, 9Y1838, 7E1041, 7C0841, 9Y1545, and 7E1043.
4MG18385
The change provides a new 9Y7450 Retainer (flyweight pin) with a different material and heat treatment. The new retainer will service the previous retainer to first production of the new style timing advance (4MG3600).
4MG25122
This change provides a 8L5832 Lock Nut (full width) in place of the former half nut. The new lock nut will service the former lock nut to first production of the new style timing advance (4MG3600).
4MG57674
This change provides two new 7E2460 Bearing Races (top hat shaped) to replace the one former bearing race. This change also provides a new high strength 093101 Ring. These changes significantly improve flyweight and race life. These new components will service the former bearing race and ring to first production of the new style timing advance (4MG3600).
4MG97295
This change provides a new 7E8097 Carrier Assembly that eliminates body-carrier slip. The preferred service method is to replace the former 7W5242 Carrier, 7C5902 Body Assembly, 8F1145 Ring, and 4W2754 Seal with the new 7E8097 Carrier Assembly back to first production of the new style timing advance (4MG3600).
5KJ465
This change provides eight mounting bolts instead of the former four for increased clamping and reduced slippage. The carrier assembly is changed to accommodate a larger 52 tooth spline. Both of these changes are needed for the 1991 emissions fuel system configuration. These changes are not adaptable to earlier engines. The components involved with change include the 4P2921 Ring, 4P2644 Carrier Assembly, 9X7715 Seal, 4P2920 Retainer, 4P2922 Plate, 4P2924 Ring, and 0T0065 Bolt.
5KJ2681
This change provides a new wider flyweight toe and race for improved resistance to wear and increased overall durability. The components involved in this change include the 4P7693 Carrier, four 4P1634 Weights, 4P1638 Screw, two 4P1635 Races, 4P1637 Spool, and 4P3337 Race. Those component are required to service back to first production of the new style timing advance (4MG3600). This change was actually released with the 4P1636 Carrier which was canceled and replaced by the 4P7693 Carrier.
3ZJ1
This change provides a new 4P7693 Carrier to replace the former 4P1636 Carrier to solve a manufacturing problem. This change will service back to first production of the new style timing advance (4MG3600). The part number of the new drive groups released are the 4P1923, 9Y5395, 4P1925, 4P1401, 4P1403, 4P1408, 4P1409, and 4P1922.
3ZJ911
This change provides a new thicker leg flyweight, race, carrier assembly, and spool. This change will help reduce the chance of fly weights binding or breaking. The carrier no longer has the acceleration noise control orifice. The components involved with this change are the 4P7693 Carrier, 4P7692 Weight, 4P7690