Usage:
3406B/C (4MG, 3ZJ, 5KJ And 8PN) Truck Engines
Changes to the timing advance drive groups are for mechanical governed engines. The changes are listed in chronological engine serial number order.
Production Serial Numbers
4MG3600
Released new style timing advance with a cone shaped cover. When compared with the former timing advance, this timing advance provides increased advance capacity (up to 12.5 degrees). The new drive group part numbers are shown in Chart 1.
4MG18385
The change provides a new 9Y-7450 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 8L-5832 Hex 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 7E-2460 Races (top hat shaped) to replace the one former bearing race. This change also provides a new high strength 009-3101 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 7E-8097 Carrier Assembly that eliminates body-carrier slip. The preferred service method is to replace the former 7W-5242 Drive Carrier, 7C-5902 Body Assembly, 8F-1145 Lock Ring, and 4W-2754 Lobed Seal with the new 7E-8097 Carrier Assembly back to first production of the new style timing advance (4MG3600).
3ZJ
This change provides new "heat set" springs that do not change load characteristics over time when exposed to engine heat. These new springs will help better maintain factory timing advance settings. See the list of Drive Groups and their corresponding new springs in Chart 2.
3ZJ1
This change provides a new 4P-7693 Weight Carrier to replace the former 4P-1636 Weight Carrier. This change will service back to first production of the new style timing advance (4MG3600). The part numbers of the new drive groups are shown on Chart 1.
3ZJ911
This change provides a new thicker leg flyweight, race, carrier assembly, and spool. This change will help reduce the chance of flyweights binding or breaking. The carrier no longer has the acceleration noise control orifice. The components involved with this change are the 4P-7693 Weight Carrier, 4P-7692 Governor Weight, 4P-7690 Flyweight Race, 4P-7691 Advance Spool, and 4P-2641 Carrier Assembly. Those components are required to service back to first production of 3ZJ1.
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 4P-2921 Guide Ring, 4P-2644 Carrier Assembly, 9X-7715 Lobed Seal, 4P-2920 Flyweight Cover, 4P-2922 Plate, 4P-2924 Drive Ring, and 0T-0065 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 4P-7693 Weight Carrier, four 4P-1634 Governor Weights, 4P-1638 Adjustment Screw, two 4P-1635 Flyweight Races, 4P-1637 Advance Spool, and 4P-3337 Flyweight Race. These components are required to service back to first production of the new style timing advance (4MG3600). This change was actually released with the 4P-1636 Weight Carrier which was canceled and replaced by the 4P-7693 Weight Carrier.
8PN10878
This change provides a new 119-2130 Governor Weight which is a service replacement for 4P-7692 Governor Weight. The governor weight toe hard coating has a new edge process to reduce chipping. This weight is serviceable back to 3ZJ911 and 8PN1.
8PN11384
This change provides a new 132-7444 Weight Carrier for the flyweights. The new weight carrier is a service replacement for the former 107-6770 Weight Carrier. The new weight carrier provides eight bolts instead of the previous four. This change further reduces the possibility of joint slip by doubling the amount of bolt clamp force. The new weight carrier attaches to a new 132-7446 Carrier Assembly which provides eight threaded holes. The 132-7446 Carrier Assembly replaces the former 4P-2641 Carrier Assembly and is serviceable back to 3ZJ1, 5KJ1 and 8PN1 by using four of the eight mounting bolt holes. The 132-7446 Carrier Assembly is serviceable back to 3ZJ1 and 8PN1.