some time i call it tcu, and other times i call it a tcm they are the same
this is from google
More images for transmission control unit location
What is a transmission control module?
or are you asking what comes with the diff.

$3780.00 includes Diff, TCU, Wave-trac, and shipping to you, ready to install .
core charge is in that price. "" you keep your TCU and Diff ""
if you want to trade in your diff and TCU, the price drops to $3280.00
if you already have a wave-trac,send it to me and I use it, and trade in your Diff &TCU , the price drops to $2280.00
any questions pm me, shipping in the USA only. jim,,, OH just re read the post,, 327,,or 3.46