Allison Transmission 3000 Mechanic's Tips page 39

• Transmission mating surfaces:
— Attaching bolts not correctly aligned
— Improperly installed or damaged gasket
— Mating surface(s) damaged
• Housing leak:
— Fill tube or plug seal damaged or missing
— Fill tube bracket dislocated
— Oil cooler connector fittings loose or damaged
— Output shaft seals worn-out or damaged
— Pressure port plugs loose
— Porous casting
• Leak at converter end:
— Converter seal damaged
— Seal lip cut—check converter hub for damage
— Garter spring missing from seal
— Converter leak in weld area or O-ring seal
— Porous casting
• Fluid comes out of fill tube:
— Overfilled—incorrect dipstick
— Plugged vent
— Water or coolant in fluid—fluid appears milky
— Incorrect electronic fluid indication
— Drain-back holes plugged
3. Visually inspect the suspected area. Inspect all gasket mating surfaces for
leaks.
4. If the leak still cannot be identified, clean the suspected area with a
degreaser, steam, or spray solvent. Clean and dry the area.
5. Operate the vehicle for several miles at varying speeds. Inspect the vehicle
for leaks.
6. If the leak source still cannot be identified, use the powder method, and/or
the black light and dye method as explained below.
b. Powder Method.
1. Clean the suspected area.
2. Apply an aerosol-type white powder to the suspected area.
3. Operate the vehicle under normal operating conditions.
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