Usage:
7251 Marine Transmissions (3.95:1 Ratio)
Description of Change: In some applications, the noise levels of 7251 Marine Transmissions with *8L9778 Planetary Groups (3.95:1 Ratio) have not been acceptable. For this reason, a new *9G7913 Planetary Group (4.00:1 Ratio) has been released. The new group uses a sun gear, planet gears, and ring gear which have a different number of teeth than the former gears. The number of teeth now used gives a different sequence of tooth contact during operation, with a better distribution of tooth loads between the gears. The result is a much lower noise level in the gear group.
NOTE: Not available as a group for parts service. At the same time, the housing group and planetary groups are changed to make the ring gear a part of the planetary group instead of the housing group. This makes all the gears part of the respective planetary groups, like other models of Caterpillar marine transmissions.
Adaptable To: The new parts, used together, are directly adaptable to 7251 Marine Transmissions 74E2499-Up equipped with 8L9778 Planetary Groups (3.95:1 Ratio). Installation of the new parts shown in the chart will change the former 8L9778 Planetary Group (3.95:1 Ratio) to the new 9G7913 Planetary Group (4.00:1 Ratio).
