Technical Bulletin # TCB15
Transmission: KM Type Units
Subject: Diagnosing TCC Slip Codes
Application: Mitsubishi / Chrysler
Issue Date: September, 2011
Intermittent Code P1740
The most commonly overlooked part during a rebuild on a KM type transmission is the o-ring located on the inside of the pump stator support in a groove on the stator shaft (figure 1). That is why it is not uncommon for a technician to have no idea that it exists in the first place. The location of this o-ring is not shown in any manuals or parts catalogs. The o-ring is extremely thin and over time becomes very brittle and begins to deteriorate. This causes a leak in the torque converter release oil circuit. A leak of this nature may cause an intermittent lockup code that won’t go away. There may also be symptoms of a converter shudder, surge or engine lugging at a stop.
The only way to remove this o-ring is to press the stator support shaft from the sealing ring side part way out to gain access to it (figure 1). It is not necessary to remove the entire shaft. Use a driver that fits just inside the outer diameter of the shaft (figure 2). Using a driver that is too large will damage the stator support. On the pump side of the stator support where the shaft is being pressed towards must be well supported around the shaft area. The stator support is not very thick and can easily crack.
Usually while trying to remove the o-ring from the shaft with a scribe or pick. The oring being very brittle will break apart into several small pieces (figure 3). Once the o-ring is seen it will remind the technician of that very thin o-ring found in the overhaul kit but never found a place in the transmission to install it.
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