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4 Posts
Discussion Starter #1
These photos are from a 2008 Sequioa SR5 5.7L without towing package, which should be the same for 2007-2013 Tundras.

Background/Story (feel free to skip this paragraph)

I bought this Sequoia as a tow vehicle for camping/vacationing, since I like the 5.7 drivetrain and the shorter wheelbase and passenger space was a bit more important (otherwise it would've been a Tundra). I wasn't planning to install a cooler. My trailer is about 3300lbs, and I was towing with my '08 Sienna 3.5L just fine (after adding lots of transmission cooling to it). However, it wasn't quite powerful enough to handle highway driving. It turned out, neither was the Sequoia! Performance was no longer an issue, but the engine kept overheating about 20 minutes into the trip and transmission temps were higher than the Sienna. After tearing apart the cooling system looking for problems, and finding none (waterpump good, no head gasket issues, etc), I discovered that the only transmission cooling present is through the coolant. I was desperate to admit failure and not abandon my new purchase, so I tried this mod and fortunately it resolved all my heating issues. Yes, engine coolant issues by installing a transmission cooler! Each time I tested it, I was hitting coolant temps over 250F after 20 minutes on the highway, with transmission temps in the 260F range. I'd slow down, downshift to higher RPMs to keep the waterpump pumping, and turn on the heat, and it was still pretty hot as I drove shamefully home. After this fix, engine coolant stays right at the thermostat setting 180F and transmission is about the same even towing highway. Ambient temperatures at the time were about mid-80s.

Parts Used
  • Cooler Assembly, Toyota part number 32970-34030 (includes thermostat)
  • Tru-Cool Max Automatic Transmission Cooler, Model LPD4921
  • Derale 3/8" Transmission Hose, 25 feet (however, 15 feet is likely plenty)
  • 4 Hose Clamps (The cooler radiator I used came with 4)
  • Transmission fluid to make up the difference
  • An oil pan or similar to catch runoff fluid
Optional Parts/Suggestions (Since refill is already a pain, drop transmission pan and replace filter)
  • Transmission Filter (no need for gasket, the stock is very reusable)
  • More Transmission Fluid
Before Starting

Since we will be draining some fluid, adding hose and a cooler, some fluid will need to be added. I wont be covering how to do that here, but it's tricky on these transmissions and I recommend becoming familiar with it before taking this on. If you're familiar with the procedure, I didn't bother entering the special mode, but filled it with a good amount, then got the temperatures in the right range and topped it off. I used a long clear hose (the excess transmission hose would likely work as well) to run it up to the engine compartment to make filling easier than a pump setup.

You may want to lift the vehicle if you need the room. Even on the Sequoia, I could probably do it without lifting it, but I put it on jacks just to make it a bit easier to get around underneath.

Parts Information

The Toyota cooler assembly fits where there is currently a "spacer", between the transmission and the "warmer". It's an expensive part, but I was able to find it much less on eBay. There are also online parts stores that might be cheaper than your local dealer. Mine came with new o-rings installed (the spacer also has the same o-rings), so no other Toyota part was needed. There are also some hard lines you could install rather than running the hose all the way. I couldn't find these priced in my range, and didn't see where they'd mount, so I skipped that part.

There was a service bulletin with these transmission coolers in cold weather where the thermostat wouldn't open and the transmission would overheat while towing. This is what made me feel like I needed a transmission cooler anyway, since the reason is because it works like a non-towing package version, which I had. I believe it applies to this generation so, to be safe, I left mine pinned (and secured the pin so it didn't fall out). This is, of course, optional based on your situation.

I chose the Tru-Cool LPD4921 for a couple reasons.
  1. When I installed coolers on my minivan, I read on the different types of coolers (tube-fin, plate-fin, stacked-plate) and got the two plate types confused. I ended up buying a plate-fin and a stacked-plate. Everyone says stacked-plate performs better, however, you need to account for airflow. They're thicker and much more dense, so require air forced through them. Not so great for going slow up a hill, so I feel that a large plate-fin is actually better for my towing concerns
  2. There are bigger coolers, but this was the largest that fit in the front bumper where I installed it
I chose the Derale hose because it was cheap and good quality. It's thicker and softer rubber than other hose I've used, which may not be want you want. Regardless of type, I recommend wiping some transmission fluid on the barb and in the hose before attempting to put them on, otherwise they go on part-way and don't want to come off.

Step 1 - Removing the Spacer, Installing the Tow-Package Cooler (Tasks - A,B,C,D)

On the passenger side of the transmission, locate the "warmer" and it's three bolts. It is shaped like a large tuna can and has a couple coolant hoses running to it.


Pic shows the rear bolt, and a portion of the front bolt (below the upper hose connection)


Pic shows the rear bolt and the third/last upper bolt

Task A - Remove the three bolts holding the "warmer" (leave the coolant hoses connected).


Pic shows warmer removed, exposing "spacer"

Task B - Remove the "spacer". It may stick a bit to the o-rings.


Spacer close up


Spacer removed (top o-ring stuck and was removed)


Cooler Assembly, left, and Spacer, right (outside)


Cooler Assembly, left, and Spacer (o-ring retrieved), right (inside)


Warmer o-rings (check that they are still there)

Task C - Make sure the original o-rings are still on the "warmer"

Task D - Install the Cooler Assembly where the "spacer" was, and re-install the "warmer" using the three bolts

I couldn't find the torque specs. Approximately as snug as before, but don't over do it. I don't think it's too picky as long as o-rings are snug.


Tow-package cooler installed (note pin for thermostat is left in)

Optional - Remove Thermostat pin
However, due to the service bulletin in cold weather, I left mine in. I actually used some wire to tie it in better so it couldn't fall out.
If you live in a colder climate and are concerned about the transmission reaching temperature under non-towing conditions, you may want to remove your pin.

Step 2 - Install Transmission Cooler Radiator

Feel free to install in your own way. For the cooler I purchased, I zip-tied it to a steel member in the bumper that had some holes in it, then zip tied the bottom so it wouldn't swing/rattle too much.

Step 3 - Hoses

I hit the picture max, so this will be continued in a later post.

However, in case I don't find time get around to it, I'll quickly explain the hose routing.
The main concern is exhaust and moving parts, but I'll do a run through of the route I took.
  1. From Cooler Assembly on the side of the transmission, down towards the front of the transmission
  2. Through an unused bracket both hoses route through
  3. Further down to frame cross-member, zip-tied using hole in member to keep it from moving
  4. Over to steel (AC if I recall) lines, zip-tied to them
  5. Up further to same steel lines, zip-tied twice (left and right of upper A-arm)
  6. There's a box in the wheel-well that let me pass to the front near the top of the frame
  7. From here, it's a straight shot to the cooler


4 Posts
Discussion Starter #2

Hose out/in from Cooler Assy on the left. The bracket is in the upper-right, in the shadow behind the outer hose.


Hoses coming from Cooler Assy, through bracket, then mount through two holes in the side of the cross member.


Hoses from crossmember, up the side to attach to AC lines. Make sure exhaust has good clearance.


Continue following AC lines to keep away from exhaust and moving parts (two zip ties here)


Pass through a hole on top of the frame, then to the cooler that's zip-tied to a metal frame (at the top)


The look from the bumper. I added bottom zip ties the plastic grill just to prevent rattling and wind flipping it up.

92 Posts
What a major PITA! Very well done DIY page, royal.fort. Clear directions, explanations, clear pictures. Good show!

115 Posts
Ditto on the 2019. How did you secure the cooler? Just zip ties? I checked behind the grill on mine, tons of clearance in there, just need a good secure mount.
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