trans cooler setup

so my next question for my new supercustom is, best setup for trans cooler!

I'm going to be doing a lot of towing of a race car, and the trans in my old van used to get hot. So, with the auto (behind 3L 1kz-te), i have been recommended two conflicting options for aftermarket cooler.
1 - plumb another cooler in front of the factory cooler pipes that go through the radiator. This way the cooler wont overcool when not towing, the radiator will allow some heat back into the fluid as it passes through. This was recommended by a diesel mechanic...
2 - mount an aftermarket cooler only and blank off the factory cooler pipes in rad. This was recommended by a transmission specialist, saying that it shouldn't get too cold when not towing...

Thoughts? who has done what? I would have thought fluid being too cold, ie when im driving to work on a cold morning would be just as bad?

Several towing owners on the Estima forum have fitted a replacement cooler matrix, blanked the rad cooler off, and not suffered any problems.
Note these are in the UK where the temp rarely gets to much less than -10 degrees C for long periods and if it does it is certainly not fit for driving in.
Never heard of there being problems with cold fluid/overcooling?

hmm ok, good food for thought. Think the transmission guys would know best too i guess. I'm hoping that by also getting rid of the trans heat away from the engine radiator, it will also reduce the risk of engine overheating when towing. Might get it fitted next week

I asked around and I understand that some Toyota auto box's have a thermal valve that does not open the cooling route until at operating temp. Maybe worth looking on toyodiy.com to see if yours has one. If so no worries!

Hi Guys

I have just finished this project on my KZH100 Super Custom 93-96 era...

I was dreading it for a while as I thought it was going to be a mission, but the actual job ended up being very easy (Less than half a day).

My van has the 1KZTE with the auto behind it, and it doesn't have the thermal valve/solenoid (no 1KZ auto that I know of has one).

Things you will need (not promoting my products but this is the way I did it):
- 10 row -8AN Oil cooler
- 4x M5x20 Machine screws with washers and nuts
- 2x -8AN 90degree Hose fittings
- 4m of -8AN Braided Hose
- 4x Braided Hose Hex Nut finishers (A clamp for attaching Braided Hose to factory hose barbs)
- 2L of ATF


Hope this step by step guide helps and I haven't missed too much: Read the complete thing before taking on the challenge

- Remove the front bumper

- Remove the front drivers seat (Most annoying part of the whole job will be the reinstall of the hand brake bracket)

- Remove the factory lines off the radiator (and put them in a small container in preparation for the next step), be prepared for a lot of trans fluid to weep out of the radiator barbs as well.

- Start the van for about 2 seconds to prove which line is the "feed" to the cooler and which is the "return" (MAKE SURE THE LINES ARE IN A CONTAINER AND STOP THE VAN AS SOON AS YOU KNOW!!!!)

- Then remove the factory rubber hose off the hard line that the fluid came out of in the above step and attach a piece of -8AN Braided Hose (with a Hex Nut(1) finisher on it), this is the factory hard line from the auto trans which "feeds" the factory cooler (in most cases the hot trans fluid is fed into the TOP of the factory radiator/cooler and returns via the bottom outlet on the radiator/cooler)

- Mount the aftermarket oil cooler (Using the M5 Machine Screws) so the fittings are facing down, it can be bolted straight to the metal bumper iron (make sure it is far enough across so it is in the "grill" of the bumper, not behind the plastic)

- Run the piece of braided hose out the rubber flap next to the drivers side top suspension arm, give the hose a decent length (it will be tied to the accelerator cable in the end) Do NOT take the hose via the middle of the van (above the AC radiator) as the auto gear linkages will hit the hoses

- Measure off the braided Hose to the mounted aftermarket cooler and fit the -8AN 90 degree fitting to the end of the hose (to be ideal this hose should go to the fitting on the right (looking at it from the front of the van), closest to the middle of the van)

- Now attach the other piece of -8AN Braided Hose (and Hex Nut(2) finisher) to the inlet of the factory cooler on the radiator (as I said above, this will normally be the top pipe), run this hose in the same place as the other Braided Hose, measure it off to the other aftermarket cooler fitting, using the last 90 degree hose fitting connect it to the cooler (if you followed what I said above, you should be connecting this to the left hand fitting).

- Then remove the piece of factory hose that originally connected the bottom of the radiator to the "return" hard line. Measure a piece of -8AN Braided Hose, cut, and put a hex nut(3&4) finisher on each end. And reinstall in place of the factory rubber hose (the idea of doing this, is the other lines are brand new, so the little effort required to make it all new is not much more).

- Cable tie the lines near the factory water radiator (best to access this with the steering wheel all the way to the right and go through the wheel arch), this is to make sure nothing can catch them near that suspension arm. Put another tie around them both to the accelerator cable under the front of the van.

- Make sure all the fittings (4x Hex Nut finishers and 2x Braided Hose fittings) are done up tight.

- Start the 1KZ, check the ATF, top it up as needed (the cooler holds a bit of fluid while running so you MUST check and top it up!), check all the fittings and hose/cooler to make sure there are no leaks

- Reinstall the Hand brake cable (nightmare!), seats, carpets, front bumper

- Recheck all fittings in 100km's to make sure nothing has come loose

Please remember:
- When you cut the Braided Hose, clean out the hose or flush with the same fluid you are planning on running through it.
- This guide is only a helper, up to you if you can do it or not, and I take no responsibility for actions you carry out and the results you have from this type of setup (I say this to cover my arse pretty much)

Reasoning for doing the cooler this way?
What are we trying to achieve? We want to cool the ATF. So if you go through your aftermarket cooler first then you have it cool, Correct? Answer is Yes and NO. It depends on the day/atmosphere.
So if you carry on through the factory cooler, if the day is hot and the aftermarket cooler doesn't quite "cut the mustard" then the factory cooler can get it to the same temperature it was going to be before. But if the aftermarket cooler does its job very well and the ATF is cool, it will then go through the factory cooler, and will heat up (sounds bad) but, you don't want your ATF too cold, so it will return at a temperature it is designed for AND remove abit of heat/load off the factory water radiator... And we all know how bad these vans are at over heating....

Hopefully I haven't missed anything off this... Please point out if you think something doesn't sound right (could be caused by different model vans).

Elusive NZ

Do you have a photographic record/diary we could all see? It would be a great help for anyone wanting to do this. Does putting the atf cooler infront of the rad not affect/reduce water cooling?

Hi Elusive,

I know this is a really old thread, but just wondering wether your trans cooling setup helped much? I'd be interested in doing the same