Usage:
3192, 7251, 7261 Marine Transmissions
- SUPPLEMENT: 12/00/87
ENGINE NEWS, SEPTEMBER 1987, PAGE 12, "More Accurate and Easier Method To Adjust 8T1815 Or 6L5438 Main Shaft Bearing" on 3192, 7251, 7261 Marine Transmissions.
The note on Page 14 has an incorrect dimension. The note should read:
--------------- END SUPPLEMENT ---------------
Reference: The sides of the spacer must be parallel to each other within 0.025 mm (.001").
Reference: Engine News; April, 1985; Page 9, "New Main Shaft Bearing Assembly Has Reduced End Play" in 7251 and 7261 Marine Transmissions. Engine News; June, 1985; Page 1, "Correct Procedure To Check Tapered Bearing End Clearances" for all applications.
Reference: Service Manual Disassembly And Assembly Modules for Above Marine Transmissions.
The first Reference Article announced an improved 8T1815 Bearing Assembly on the main shaft of the 7251 and 7261 Marine Transmissions. (The same bearing is also serviced for the 3192 Marine Transmissions.) Cross out the last paragraph of this article, and refer to this new article. A more accurate adjustment procedure with a fabricated preloading device is now available and should be used when the bearing end clearance is set. This same procedure and the same spacer thickness can also be used on the former 6L5438 Bearing Assembly if it does not need to be replaced.
NOTE: Refer to second Reference Article and, after the subtopic, write "Except 3192, 7251, 7261 Transmissions", and cross out the first paragraph referring to the earlier Engine News article. Also, add a note to the Service Manual modules referring to this new article.
If the bearing end clearance is too much, the half of the bearing which is unloaded can have a bearing separator failure. The fabricated preloading device is bolted to both sides of the 8T1815 Bearing Assembly to provide a constant preload during the entire procedure.
Make all the necessary pieces for the preloading device as shown in Illustration 1. Also, see Illustration 3 for the load springs and additional hardware needed.
Illustration 1. Details for making the load plate and the two half-moon plates.
Measurement And Adjustment Procedure:
1. Assemble only the parts shown by the shading in Illustration 2. Do NOT install the spacer between the bearing cups, and do not install the shaft assembly in the case.
Illustration 2. Only the shaded parts are to be assembled for this new bearing adjustment procedure.
2. Assemble the preload pieces as shown in Illustration 3. The two half-moon clamps go next to the top and bottom of the inside bearing cup. See Section A-A. Tighten the four inside nuts tight against the half-moon shaped clamps. These nuts are to function as jamnuts.
3. Support the shaft in a HORIZONTAL position.
Illustration 3. Assembled view of the load plate, clamps, rods and springs that are used to correctly load the bearings.
4. Tighten the four nuts to compress the springs to the length shown in Illustration 3. This particular step assures that the correct load shown is evenly spaced all around both bearing cups to help seat the bearing rollers against the cone ribs.
5. Before rotating the bearings, measure the distance between the bearing cups to get an idea of how much the cups will move together after they are turned a few revolutions.
6. Rotate the fixture and the bearing cups three or four revolutions.
7. Inspect the ends of the rollers to be sure they are seated against the cone ribs.
8. Make four measurements at 90° intervals of the gap between the cups. Record each measurement and compute the average.
9. Repeat Steps 6, 7 and 8.
10. You now have two average measurements. If there is a difference of more than 0.03 mm (.001") between the two average measurements, repeat Steps 6, 7 and 8 as often as needed until you are sure that the rollers have moved back against the thrust shoulders (cone ribs) of the bearing cones. This assures that the outer races have, therefore, moved together as close as possible. When these conditions are met, the measured gap between the bearing cups is as small as possible all the way around, and this is the determining dimension for the correct width of the spacer needed between the cups.
11. Grind the bearing spacer on a surface grinder until its width is 0.10 ± 0.03 mm (.004 ± .001") MORE than the final measured gap. (A spacer in good condition from the 6L5438 Bearing Assembly can also be used.) This additional width is the desired amount of end clearance for either the 8T1815 or the 6L5438 Bearing Assembly.
NOTE: The sides of the spacer must be parallel to each other within 0.25 mm (.001").
12. Install the ground spacer between the cups and reassemble the transmission. The bearing end clearance will remain 0.10 ± 0.03 mm (.004 ± .001").