PUMP GP-GEAR 6Y8764 - Caterpillar

3408 And 3412 Marine EnginesSUPPLEMENT: 11/25/81ENGINE NEWS; AUGUST 13, 1980, PAGES 2 AND 3.In the article, "Two New Front Power Take-Off Groups Are Available," under the subject, "Service Information," change the first paragraph to read as follows:
"During reconditioning, install the clutch assembly on the tapered shaft and tighten the nut to move the clutch assembly to its seat. The nut must be tightened to 41 N m (30 lb ft) plus 60° to 90° for single-disc clutches and 41 N m (30 lb ft) plus 120° to 150° for double-disc clutches. Bend a tab on the lock against a flat on the nut."
--------------- END SUPPLEMENT ---------------Two new front power take-off groups are available for use on 3408 and 3412 Marine Engines. The 5N7399 Front Power Take-Off Group has a single-disc clutch, and the 5N7400 Front Power Take-Off Group uses a double-disc clutch.
Both of these new front power take-off groups use two bearings, which are kept apart by spacers, in front of the clutch. This design keeps the clutch on the same center line as the crankshaft without the need for a crankshaft pilot bearing or an external bearing.
The result is less vibration between the clutch and crankshaft, which can cause a clutch failure.
Formerly, a pilot bearing was used. Later clutches did not have a pilot bearing. Instead, a longer shaft and an external bearing were used.
Alignment Of Front Power Take-Off Groups
Correct alignment of the new front power take-off groups is very important. The new groups' alignment is controlled by the runout (full indicator movement or tota indicator reading) of the adapter and bore-to-crankshaft center line, and the runout of the housing pilot and face in relation to the clutch shaft center line. Since the factory tolerances control the alignment of the parts, they control the alignment of the front power take-off group with the crankshaft. Correct installation prevents alignment changes.
The earlier groups' alignment was controlled by either the pilot or external bearing.
It is Caterpillar's recommendation that the steps which follow be used during installation, to make sure the front power take-off group is in correct alignment with the engine. If the front power take-off group was a separate purchase and did not come installed on the engine, begin with Step 1. If the front power take-off group came as an installed attachment, begin with Step 6.
1. With the engine installed in the boat, install the 5N7751 Adapter with eight S1573 Bolts tightened to a torque value of 115 15 N m (85 11 lb ft) and install the 3L8029 or 4B4805 Drive Ring with eight S1591 Bolts.2. Put a dial indicator in position to read the total vertical movement of the crankshaft at the top of the drive ring. Use a lever to move the drive ring and crankshaft upward and read the indicator total movement. do not put force against the adapter housing because it will move the dial indicator base.
Do not use any more force than is necessary to move the crankshaft.
3. Fasten the