Planetary gearset. Bands

Planetary gearset

DESCRIPTION

The planetary gearsets (Fig. 58) are designated as the front, rear, and overdrive planetary gear assemblies and located in such order. A simple planetary gearset consists of three main members:

  • The sun gear which is at the center of the system.
  • The planet carrier with planet pinion gears which are free to rotate on their own shafts and are in mesh with the sun gear.
  • The annulus gear, which rotates around and is in mesh with the planet pinion gears.

NOTE: The number of pinion gears does not affect the gear ratio, only the duty rating.

OPERATION

With any given planetary gearset, several conditions must be met for power to be able to flow:

  • One member must be held
  • Another member must be driven or used as an input.

Fig. 58 Planetary Gearset Fig. 58 Planetary Gearset

1 - ANNULUS GEAR

2 - SUN GEAR

3 - PLANET CARRIER

4 - PLANET PINIONS (4)

  • The third member may be used as an output for power flow.
  • For direct drive to occur, two gear members in the front planetary gearset must be driven.

NOTE: Gear ratios are dependent on the number of teeth on the annulus and sun gears.

Bands

DESCRIPTION

KICKDOWN (FRONT) BAND

The kickdown, or "front", band (Fig. 59) holds the common sun gear of the planetary gear sets. The front (kickdown) band is made of steel, and faced on its inner circumference with a friction-type lining.

One end of the band is anchored to the transmission case, and the other is acted on with a pushing force by a servo piston. The front band is a single-wrap design (the band does not completely encompass/ wrap the drum that it holds).

LOW/REVERSE (REAR) BAND

The low/reverse band, or "rear", band (Fig. 60) is similar in appearance and operation to the front band.

OPERATION

KICKDOWN (FRONT) BAND

The kickdown band holds the common sun gear of the planetary gear sets by applying and holding the front clutch retainer, which is splined to the sun gear driving shell, and in turn splined directly to the sun  gear. The application of the band by the servo is typically done by an apply lever and link bar.

Fig. 59 Front Band Fig. 59 Front Band

1 - FRONT BAND

2 - TRANSMISSION HOUSING

Fig. 60 Rear Band Fig. 60 Rear Band

1 - REAR BAND

2 - BAND LINK

LOW/REVERSE (REAR) BAND

The rear band holds the rear planet carrier stationary by being mounted around and applied to the low/reverse drum.

    Dodge Durango (DN) 1998-2003 Service Manual

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