1979/03/14 Caterpillar

Correct maintenance and overhaul procedures are important for acceptable service life of the front power take-off (FPTO) for 3408 and 3412 Marine Engines. Owners, operators, and dealers must use the correct maintenance procedures that follow, with special importance put on regular maintenance intervals.

Dealer Maintenance

A) Adjustment of Force Needed to Engage FPTO:

The force needed to engage the new FPTO units must be checked with a spring scale before the FPTO units are put into service. After the first 10 hours of operation, the force must be checked again and the clutch adjusted if necessary. During the first 10 hours or "wear-in" interval, it is possible several adjustments will have to be made until the plates are "worn-in". After "wear-in" check the adjustment whenever the boat is available.

A wrong adjustment of the force can cause slippage, which can cause excessive (too much) plate wear, plate cracking and FPTO failure.

Use the procedure that follows to adjust the front power take-off clutches:

1. Disconnect any linkage from the clutch lever (if so equipped).

2. Measure distance (x) as shown in Chart A. Distance (x) is the dimension from the center of the shaft to a location on the clutch lever where the spring scale will be fastened to measure the amount of force needed to engage the clutch. Fasten a spring scale at the correct location on the clutch lever. See chart A.

A torque wrench with a 8S2243 Retainer Nut or 5P1668 Nut can also be used to measure the force needed to engage the clutch. Install the torque wrench and nut to the engagement shaft on the end opposite to the lever. The minimum and maximum torques needed to engage the clutch are given in the Chart B.

3. Keep the angle between the clutch lever and the spring scale at 90°. Pull the spring scale in the direction shown in the illustration until the clutch engages. Make a record of the amount of force needed to engage the clutch. Check the chart for the correct amount of force needed to engage the specific clutch.

4. If the amount of force needed to engage the clutch is not correct, remove the inspection cover. See Illustration 1. Turn the clutch until the lock pin can be seen through the inspection opening. Release the push-type lock pin and turn the adjustment ring clockwise as seen from the rear of the clutch to increase the force needed or counterclockwise to decrease the force needed to engage the clutch.

Illustration 1. Location of parts in FPTO.

5. Check the amount of force needed to engage the clutch again. Adjust the adjustment ring until the force is correct. After each adjustment check the lock pin to make sure it is in a notch.

6. The initial adjustment must be checked frequently to prevent slippage during the break-in until the clutch disc has a good seat.

7. The new adjustment specifications take the place of the former specifications that are on the clutch identification plates and those given in the Service Manual. If the specification on the clutch identification plate is different from the new specification, change it to the new specification.

NOTE: When more force than the maximum force is needed to engage the clutch, failures of FPTO components can result. Always be sure the FPTO has the correct lubrication before any adjustment is made.

B) Adjustment of the Vessel FPTO Engagement Linkage Travel:

The engagement linkage used on the vessel to connect the FPTO engagement lever to the deck top handle must have enough travel so the FPTO can be fully engaged and disengaged. Boat manufacturers usually give enough linkage travel so it is necessary during FPTO installation to be sure the correct connection is made between the vessel's linkage and the FPTO lever. Not enough linkage travel for engagement can cause clutch slippage. Not enough linkage travel for disengagement can cause excessive (too much) collar wear and sliding sleeve failures.

The deck top engagement handle must not have any bolts, stops, or hooks that hold the lever in the engaged position. During engagement, the FPTO linkage must seek (find) its own position. If the lever is held in the engaged position, it will load the collar and cause collar and sliding sleeve failures.

C) Adjustment of Main Tapered Roller Bearings:

The main tapered roller bearings must be adjusted to the correct FPTO end play to get good bearing life. The 5N1729 and 5N1730 FPTO's for 3408 and 3412 Marine Engines use a 2N9363 Bearing Retainer Nut that gives easy bearing adjustment. Use the procedure that follows to adjust the main tapered roller bearings:

1. Install the PTO clutch shaft, bearings and retainer nut in the housing. Lubricate the bearings lightly by hand. Do not fill the housing with grease.

2. Tighten the retainer nut until 60 lb in (6.8 N·m) of torque is needed to turn the shaft. This will remove any shaft end play.

3. On arrangements where a side load from the FPTO shaft is used, such as a pulley and V-belt, turn the retainer nut backwards one to two notches. This will give the correct shaft end play of .004" to .007" (0.10 mm to 0.17 mm). On arrangements with in-line power take-off from the FPTO shaft, such as a U-joint or flexible coupling, turn the retainer nut backwards two to three notches. This will give the correct shaft end play of .007" to .009" (0.17 mm to 0.23 mm).

4. Lubricate the bearing with a grease gun to fill the bearing cavity.

D) Installation of FPTO Pilot Bearing:

During assembly of a FPTO, install the pilot bearing to a dimension of 3.89 ± .05" (98.8 ± 1.3 mm) measured from the rear face (engine side) of the bearing to the mounting surface of the power take-off housing. When correctly installed, the bearing will extend .10" (2.5 mm) beyond the end of the shaft to even with the end of the shaft. If the bearing is pushed too far on the shaft, the bearing will be damaged by the hub nut on the shaft.

During installation of the FPTO to the engine, multipurpose type grease (MPG) which contains 3% to 5% molybdenum disulfide (see Operator's Manual for the exact grade of lubricant) must be put on the outside of the pilot bearing where it comes in contact with adapter bore on the engine. After the FPTO has been installed, hit the end of the clutch shaft with a soft hammer. This will remove any pre-load from the pilot bearing.

Before installation of the FPTO into the pilot bearing bore, check the pilot bore for wear. If the pilot bore is worn, a replacement adapter will have to be installed.

E) Wave Washer Installation on Linkage Components:

There are a total of nine pivot pins for each FPTO internal engagement linkage, three per link between the 2L8259 Lever and the 5N4160 Sliding Sleeve. During service work, install the flat washers and spring washers shown in Illustration 2 to remove side-play within the linkage. Also, add a 5B6172 flat washer beneath the cotter pin if space is available. After a high number of service hours, wear on the linkage components can make it necessary to install additional washers. If the linkage components are worn excessive they must be removed and new components installed.

Excessive side-play within and between linkage components can cause early component wear and failure.

During assembly of the internal FPTO engagement linkage, the old cotter pins must not be used again. Always install new 6L3964 Cotter Pins.

Illustration 2. Location of washers in linkage components.

F) Installation of Pulley on FPTO Shaft:

During installation, the pulley must be moved on the shaft as far as possible toward the FPTO housing. The driven pulley and belt tightener must be put in position accordingly. This gives minimum side load on the bearings which extends bearing and general FPTO service life.

G) Replacement of Clutch Parts:

During any major service work, it is important to use only 5N1729 or 5N1730 Clutch Kits on 3408 or 3412 Engines. Clutch kits for the D343 Engines will shorten the service life if used on 3408 and 3412 Engines.

Operator Maintenance:

A) Adjustment of FPTO Engagement Force:

The owner must be made aware of (shown) the correct adjustment procedure used by the dealer, and the importance of several adjustments during the "wear-in" interval.

If the operator has a spring scale or torque wrench, he can easily adjust the clutch with the same procedure given under Dealer Maintenance. If these tools are not available, the clutch is to be adjusted and the engagement force increased until the clutch engages with a "solid and distinct snap" equal to (the same as) the recommended force.

NOTE: Always be sure the FPTO has the correct lubrication before any adjustment is made.

The engagement force is to be measured on the FPTO engagement lever, not on the deck handle, since the vessel's engagement linkage can soften the needed feel for the engagement "snap".

If the FPTO slips under normal load conditions, use the procedure that follows:

1. Adjust the FPTO one notch at a time with the adjusting nut until the FPTO does not slip under normal load conditions.

2. Increase the engagement force by one additional notch on the adjusting nut.

3. The FPTO must engage with a "solid and distinct snap" equal to the recommended force.

Under no condition must the deck top engagement handle be held in the engaged position. The FPTO linkage must seek its own position. If the lever is held in the engaged position it will load the collar and cause collar or sliding sleeve failure.

B) FPTO Lubrication:

All lubrication maintenance must be done regularly. There are three areas that need grease on the FPTO (see the Owner's Manual for the exact location of each grease fitting).

1. Lubricate the engaging collar every day. Use approximately one full stroke of a grease gun.

2. Lubricate the control lever shaft bearings every week. Use approximately one full stroke of a grease gun per fitting (2 fittings total).

3. Lubricate the main shaft bearings every week. Use approximately two full strokes of a grease gun.

4. Engage and disengage the FPTO several times to get good lubrication to all of the parts.

C) Installation of the Inspection Plate:

Every FPTO unit is equipped with an inspection/specifications plate on the housing. This plate must be installed after maintenance to keep water and foreign materials out of the FPTO.