Under the "firm shift" option a tuner will allow you to set, hard shifts at high RPMs, can cause fluid to blow out the vent. That ends up in the Bell Housing, and leaks out the bottom of the trans, and you may think that you have a pump leak at the trans. A catch can will prevent fluid loss, and you can top off fluid through the catch can. I bought the same can I used for the PCV oil catch. PRODUCT ($25.0 on eBay): You won't need the baffle. I plugged the top, and the inlet, and put the filter on the outlet side. You also don't need the dip stick. You can bolt that up too, like I did, you will see that below. Drilled and tapped a hole in the bottom of the can for the fitting: Here is what the Vent looks like, it's the hose on the top of the trans. It is not exactly the same for all models, but it goes into the bell housing regardless of how many points on the trans housing it's connected to: Yes, it says 5R55W, the picture is for illustration only, the 5R55S has the same vent tube. It is NOT easy to disconnect the vent hose from the bell housing. I used a 2 foot screwdriver and and broke it off at the bell housing. Then I cut it back an inch because when it broke, part of the plastic fitting stayed in the hose. After that I installed a coupler into the hose, and ran the other hose to the bottom fitting of the catch can: Line runs down, and ties into the transmission's vent tube. I also removed the level dip stick and fastened a relay that I use for something else. So, as you can see, the top, and inlet is plugged, and the outlet is vented. Later, I took the top plug out, and filled the can with Lucas Trans conditioner: You can see the red coloring in the hose, as it drained down into the transmission. I started it up, and cycled though the gears for a few minutes. I checked the tube after, and it was clear. JDM makes a kit for the 5R55S, so this is nothing out of the ordinary. However, their kit is $159.00, and this is what it looks like: There are no instructions at their site, or any site that sells it. They only say to drill holes in the can, and mount it to the firewall somewhere; and no indication as how you're supposed to pull the trans vent line out of the bell housing. That JDM also works for a rear diff reservoir/catch for racing with hard cornering.