I know that this write up has been done before, but I had some unanswered questions when I went to do mine, so here is my write up:
The parts I used:
B&M cooler #70268 from Summit Racing
2- 3/8 to 3/8 hose barb connectors (home depot)
2 additional hose clamps for a 3/8 ID hose
1 quart of Mopar ATF-4 Tranny fluid
1. Remove the front grill. Use a Philips screwdriver to remove the 6 plastic retaining screws (for on 07 for an 08, you will just pop them off with a flat head). I used a flat head to pop the retainers out after that.
2007 Grill Screw
2008 Grill Clip
The grill will just pop off dont forget to unplug the parking lights.
2. Unpack your cooler.
The mounting orientation of the cooler is VERY important. I called B&M on this, because I was not sure. The least efficient way to cool is by having the hose outlets facing down. The MOST efficient is to have the cooler mounted with the outlets up or on the side. If you choose on the side, make sure the INLET (from the factory cooler) is on the bottom and the top hose goes to the tranny. This is VERY important.
I did not feel comfortable pushing the plastic zip tie things through my condenser and radiator, so I mounted my cooler with the supplied brackets. This also puts the cooler a couple inches away from the condenser for better cooling. I cut the brackets to length with a Dremel and used the supplied hardware to bolt it in. I had to drill holes in the lower grill brace to bolt the lower cooler brackets to. You could paint your brackets black (which would look nice) I did not.
3. Route the first hose from the bottom of the cooler under the Jeep and to the upper tranny hose. Make a cut here. Use the remaining hose, and run it from the top of the cooler, route it the same way to the same location. Note which hose is which. At this point, attach a 3/8 hose to 3/8 hose barb adapter to the end of each hose and secure with a clamp.
4. Next, I put the font of the Jeep back together (remember to plug the lights back in!).
5. Place a drain pan under the tranny hoses. Get 2 hose clams ready, use some cutters, and cut the UPPER tranny line in the center of the rubber section. I worked from the top (under the hood). Slide a hose clamp on each side of the tranny line and slide the hoses with the hose barbs into the tranny lines. The one from the bottom of the cooler will go to the hose coming from the front of the Jeep. The one from the top of the cooler will go to the hose going towards the transmission. Secure the clamps. Wipe up the little tranny fluid that dripped.
Crawl under the Jeep, check the hoses to be sure they are not hanging. If so, secure them. Take it for a drive and get it good and warm. Check the fluid. I had to add about half a quart.
This dropped my temp from ~220 to ~170 (on the Unlimited with 4.10's)