About four or five years ago, John Parmenter from Centereach Transmission revealed a no Park problem that could occur with a Nissan RE5R05A Transmission. There was an insert in the back of that would stick in the case but would fall out unnoticed in the parts washer. When the transmission is reassembled and installed into the vehicle, the parking rod is not capable of engaging park with this insert missing. The steel insert allows a lift off point for the bullet end of the rod to be able to wedge the parking pawl into the parking gear.
The same can happen with the RC4A-EL transmission as it utilizes the same basic design. Figure 1 is a photo showing the insert in place while figure 2 shows the insert removed. Depending on the condition of the fluid (figure 3), this piece becomes covered with thick burned fluid disguising it as being a part of the case. Once it is in a heated parts washer it may or may not dislodge itself. If it does, and you are unaware, you may encounter the No Park No Teeth experience. If this one got past you, the good news is, it can be an in-car repair by simply removing the extension housing.
