According to the CRG link provided ( THANKS ED! ), I guess it is a Julian date code. However, it rolls over into the next year.
So this transmission was assembled on the 29th of January 1969. That makes sense because it came from a early March '69 L/78.
Now, the 2160 is a sequence number according to the same link. What exactly is a sequence number? Was it the 2,160th THM400
built that model year, or the 2,160th Turbo-Hydramatic built? Anyone know exactly what the sequence number represents?