Usage:
7251, 7261 Marine Transmissions
Description of Change: A new, double tapered roller bearing assembly is used in the main shaft group in 7251 and 7261 Marine Transmissions. The new bearing assembly will reduce the bearing end play and improve the service life of the transmission.
With the former bearing assembly, excessive bearing end play could allow the unloaded rollers in the bearing assembly to move sideways and cause a failure of the transmission.
Adaptable As: The new 8T1815 Tapered Roller Bearing Assembly, part of the 4L4319 Main Shaft Group, is a direct replacement for the former 6L5438 Tapered Roller Bearing Assembly.
Use the procedure given in the Service Manual and assemble the shaded parts shown in Illustration 1. Install this subassembly into the transmission case and measure the bearing end play with a dial indicator. If bearing end play exceeds 0.2 mm (.008"), use a surface grinder to grind the bearing spacer (see Illustration 2). The bearing end play can be reduced in direct proportion to the amount of material removed from the bearing spacer. Bearing end play should be between 0.10 mm and 0.15 mm (.004 and .006").
Illustration 1. Check end play of main shaft group.
Illustration 2. 8T1815 Tapered Roller Bearing Assembly.