LINK AS-TRACK 1061634 - Caterpillar

3192, 7251, 7261 Marine TransmissionsDescription of Change: A change to the inside diameter of the astern (reverse) drive shaft reduces the volume of oil forced through the astern clutch when the ahead (forward) clutch is engaged. This reduces the horsepower loss in the free-wheeling astern clutch by about 9 kW (12 hp) at 1600 rpm because there is less oil drag in this clutch. At the same time, more oil is being forced through the engaged ahead clutch. This gives additional cooling to the ahead clutch. This change is a result of increasing the oil restriction inside the forward end of the astern drive shaft, and enlarging the two cross-drilled holes in the shaft at the ahead clutch location. See illustration. The inside diameter in the ahead end of the shaft is reduced from 47.63 mm (1.875") to 41.28 mm (1.625").
Adaptable To: These improvements are effective with 7251 Transmission 74E2436, and 7261 Transmissions 89B777 and 6LB191. The improved 4L4295 Shaft (part number did not change) is directly adaptable to earlier 7251, 7261, and 3192 Marine Transmissions. Earlier 4L4295 Shafts can be modified when the transmission is reconditioned. Machine the ahead end of the shaft, and press in a locally made steel bushing as shown. Enlarge the two 10.72 mm (.427") oil holes.
Modifications To former astern drive shaft.