Planetary Gear Failure

Author: Subaru

Printable Version | Submit Feedback

NUMBER: 16-59-94

DATE: 04-20-94



Whenever the 4EAT is being repaired or replaced with a new or remanufactured unit, it is very important to ensure that a quality repair is being performed. A shop comeback is frustrating, detrimental to customer satisfaction, and not a matter for warranty. It is also avoidable.

In addition to replacing any damaged parts and making all of the required precision measurements, a thorough inspection must be performed. The failed parts, replacement parts, and the affected circuit must be closely examined. This must be done to determine the cause of the failure and to ensure that it does not happen again.

When performing a repair to the rear planetary gear section of the 4EAT you are repairing an effect; for every effect there is a cause which must be found. The following are causes for rear planetary failure which have been documented:

  1. Restricted flow through the radiator cooler.
  2. Kinked or obstructed radiator cooler lines.
  3. Improper ATK-50 filter kit installation or hose routing.
  4. Debris restricting ATF flow through the input shaft or its oil feed holes.
  5. Reuse of a heat damaged input shaft (where the internal seal has become deformed).
  6. Orifice plug missing from the rear of the reduction shaft (see Item 1 in Figure 1).
  7. Bushing missing from the front of the reduction shaft (see Item 2 in Figure 1).

By ensuring that the above items are checked on the vehicle and on the parts being reinstalled into the transmission case (both new andused), you are ensuring a quality finished product.

To return to the Technical Service Bulletins index click here.