2nd Gen Non-Engine/Transmission Heater Questions

[24valver]

While putting the new turbo on my truck I noticed something missing. When you stand at the front looking at the engine, under the turbo and to the right there should be a canister with lines going to it (at least their is on a 97). I don't know what its called, but I'm assuming that it has something to do with the heater. Could you all tell me what it is and what it does? Thanks

 

[24valver]

WEll, after looking through my service manual, I figured out that it is an automatic transmission cooler. I was looking at my Moms truck, but mines a manual.