1998/06/01 Caterpillar

Timing Hole In Wrong Location In Allison Flexplates{1003}

Usage:

3176 (2YG, 7LG),
3176B (9CK),
C-10 (2PN, 8YS),
C-12 (1YN, 9NS) Truck Engines Equipped With Allison HD Series Transmissions

If the above truck engines are equipped with an Allison HD Transmission, the Allison Flexplates on these engines have the pin timing hole in the WRONG location. The use of this pin timing hole to time the engine could result in damage to engine valve train components.

DO NOT use the pin timing method to time the above engines equipped with Allison HD Transmissions. Use the following method to adjust the valves and the fuel injector prestroke.

1. Remove the engine valve covers.

2. Rotate the engine crankshaft in the normal direction of engine rotation (clockwise when viewed from the crankshaft damper end of the engine).

3. Observe the operation of the inlet and exhaust valves on the number 6 cylinder (the number 6 cylinder is closest to the flywheel end of the engine).

4. Stop rotation of the engine when the exhaust valve (long rocker arm) closes and the inlet valve (short rocker arm) starts to open.

5. Check to be sure the number 1 piston is at Top Center (TC) of the compression stroke by trying to move the rocker arms for the number 1 cylinder by hand. If the rocker arms can be moved by hand, the piston is at TC of the compression stroke. If the rocker arms can not be moved by hand rotate the crankshaft 360 degrees and repeat Step 5.

6. Place a reference mark on the crankshaft damper and the front cover.

7. With the number 1 cylinder at TC of the compression stroke, adjust the valve lash and fuel injector prestroke as needed for:

* The number 1, 3 and 5 cylinder exhaust valves.

* The number 1, 2 and 4 cylinder inlet valves.

* The fuel injector prestroke for the number 3, 5 and 6 cylinders.

8. Rotate the engine crankshaft 360 degrees, stopping when the reference marks (from Step 6) are aligned.

9. Adjust the valve lash and fuel injector prestroke as needed for:

* The number 2, 4, and 6 cylinder exhaust valves.

* The number 3, 5, and 6 cylinder inlet valves.

* The fuel injector prestroke for the number 1, 2, and 4 cylinders.