After installing the TRD Supercharger I noticed my transmission temperatures seemed to run about 20 - 40 degrees warmer depending on driving style, ranging from 200* - 220* where as before the supercharger temps would hover around 180* F. I'm not sure if this is a result of the supercharger itself, or a side effect of having more power on tap causing me to give a little more throttle than I did naturally aspirated. In either case, a transmission cooler is a good idea for any automatic transmission and they're cheap to boot. After looking at several offerings, I decided on the Tru Cool 4454 which is good for an 18,000 pound GVWR, is a low pressure drop design, is compact at 7.25" x 11" x .75", and includes hardware for two different mounting options. The low pressure drop design means it allows cold transmission fluid to flow through larger passages allowing the fluid to bypass the cooler to reach operating temperature faster and avoid over cooling in cold weather. As of this writing the price was around $60 US making it a bargain.
For this modification you'll need:
About 4' of 3/8" transmission cooler hose (4' of 5/16" transmission hose comes with the cooler)
8' of 3/4" heater hose
Mounting hardware needed in addition to what comes with the True Cool 4454:
(2) 1.25" x 1/4 x 20 bolts
(2) .75" x 1/4 x 20 bolts
(8) 1/4 x 20 nylon lock nuts
Dremel Tool with cut off wheel and sanding wheels
Basic hand tools such as box end wrenches and socket set
Needle nose pliars
2 quarts of automatic transmission fluid
Drill with 1/4" bit
1 foot vacuum line
To make this as easy as possible I highly recommend you remove the grill as well as the front bumper. This will give you plenty of working room and visibility for mounting. Removing the grill is a no brainer with small plastic clips. The front bumper is simply 6 bolts.
Decide where you want to mount the cooler. I spent about 45 minutes looking it over before deciding to mount it in the center lower area. I found two factory screw holes, one was used by a ground strap wire bolt, and the other wasn't used at all, along the support that the skid plate attaches to. I drilled two 1/4" holes in the front clip cross member for the upper mounting location. I feel this works the best as it gets the cooler down low enough to sit behind the opening in the air dam, it's out of the way of all body mount points, and it keeps the hoses at a large radius where they bend to connect to the cooler's input and output. After several test fits, I had the brackets bent and cut to give a factory installed appearance and a secure mount.
I then mounted up the brackets using the 1/4 x 20 bolts and nylon lock nuts.
I've seen a lot of folks run their cooler lines around the passenger side tow hook and over the frame to get them to the stock transmission line areas. I never liked that implementation as I felt it left these hoses exposed to damage. If one of these hoses gets cut or leaks, you're dead in the water. I took a look over the front clip and thought about how Toyota might have routed these lines had they installed this cooler from the factory. I noticed they ran the A/C lines through an opening in the front clip so I decided that's how I'd route my cooler lines.
I used a Sharpie and traced out an area just below the A/C lines that I'd cut out being sure there were no lines or wiring behind the area. I then drilled holes at each corner and used my Dremel Tool with cut off wheel connecting the dots to remove material. I then used the Dremel Tool with sanding wheel to take the sharp edges off the cut area, applied a quick shot of black primer to prevent rust, and put some slit vacuum line over the metal edges for added abrasion protection. I then put some 3/4" heater hose over the cooler lines as an added level of abrasion protection and routed the cooler lines to the engine bay.
Finally I connected the driver's side port on the Tru Cool 4454 to the output of the stock transmission cooler, which is located in the bottom part of the radiator, using the kit's included 5/16" transmission line. The connection point for the stock transmission cooler output was on the driver's side of my 2002 model 4Runner, but you'll want to verify yours to be sure. I then connected the passenger side port on the Tru Cool 4454 to the factory hard return line which is located just above the front cross member using the 3/8" transmission line I purchased. Be sure to use transmission line and not fuel line for these connections. Routing the lines in this fashion is the best solution as it allows the stock cooler to do it's job, then it's cooled further by the Tru Cool unit before returning to the transmission.
I zip tied where appropriate to avoid abrasion and to facilitate a clean install. When disconnecting the stock transmission lines from the stock cooler and hard line have a container on hand to capture the quart or so of fluid that will come out. This is only the fluid left in the lines and will not drain the transmission.
I fired up Project SportRunner and tested for leaks then took it for a test drive to get everything up to operating temperature. I then added fluid as necessary and re-installed the bumper and grill. Be sure to check the fluid with the vehicle at operating temperature and with the engine running.
I've noticed about a 20 - 30 degree drop in transmission temperatures since installing the cooler with cruising temps around 160* - 170* F and 180* - 190* F under hard driving.