A/T - ATX Planetary Gear Interchange
Technical Bulletin # 100Date: March 1992
To date, there have been three different types of planetary gears used in ATX units. Refer to the information in this bulletin to identify the individual components.
1981-1984 used Type # 1
1985-Early 1986 used Type # 2
Late 1986-Present used Type # 3
SUN GEAR
1. Count the sun gear teeth. There are only 2 different sun gears:
Type # 1 = 29 teeth
Type # 2 & # 3 = 31 teeth
RING GEAR
1. Count the teeth
2. Measure the height
Type # 1 = 86 teeth-2 7/8" tall
Type # 2 = 94 teeth-2 7/8" tall
Type # 3 = 94 teeth-3 3/4" tall
PLANETARY GEARS
Type # 1
17 TOOTH-TALL PINIONS
Type # 2
19 TOOTH-TALL PINIONS
Type # 3
19 TOOTH-"SPLIT" PINIONS
REAR DRUM
1. Count the teeth
2. Measure the height from the top edge of the sun gear to the thrust washer surface:
Type # 1 = 52 teeth
Type # 2 = 56 teeth-7/8 inch
Type # 3 = 56 teeth-1 inch
^ Interchanging entire planetary systems between type # 1 & type # 2 is OK. Do not install a type # 1 or # 2 in place of a type # 3.
^ Certain component mismatching is impossible, because different tooth counts won't allow the parts to mesh together during assembly.
^ Some component mismatching will cause no endplay or the unit locks up when the pump bolts are tightened.
EXAMPLE:
A type # 3 drum installed with a type # 2 planetary.
^ Using a type # 3 planetary with a type # 2 ring gear will cause no forward movement but good reverse.