I'm curios to know, can I reuse the copper tube (portion of the cooler that's inside the rad tank)
as an external cooler mounted in front of the rad ?

I'm asking because I recently replaced the old radiator in a family members AUII (tank exploded) so I've cut the cooler tube out just to see what makes it tick.
Now though, I'm thinking it may be used as an external cooler just on its own.

So if I re-route the cooler pipes (to passenger side of rad) & mount the copper tube vertically in front of the rad, would that be enough to keep the transmission cool ?

My thoughts are, open air flow around the copper tube V's submerged coolant flow & the different thermal qualities of both environments.
I'm thinking open air flow would cool the copper way more efficiently than being submerged in boiling coolant...

...& also, what's the nominal running temp of a trans & what would the outcome be should the trans run a bit cooler ?
Worst case scenario would be that the trans slowly overheats if the fluid isn't cooled enough before going back to the trans.
(also note the fins inside the copper tube to restrict flow)

Your thoughts...

buy a proper cooler as the fins allow greater heat dispersal with the greater 'area' for air to flow over/thru. but if you want to use the tube ... go for it.

"Buy a proper cooler".....

Only took 12 hrs for the peanut gallery to chip in. Thanks for stating the obvious.

I won't buy a proper cooler as I don't need one.

My bad I guess, for asking a question on a public forum... you'd think I'd have learnt by now!
Sorry for disturbing you, back to your peanuts now ok.

WHAT!!! .... you didn't bring ANY peanuts


i actually said more than just "buy a proper cooler" - i also said why.


also it was less than 12 hours

Last edited by Mad2 on Sun Aug 18, 2019 11:22 pm, edited 1 time in total.

Theoretically it should work-but I think by itself as it is may not be very reliable in the long term-but no harm in trying as you just never know hey!
Cheers Johnny.

Couple of points;

1. The reason the oil cooling was done in the water radiator was to bring the temperature of the transmission up to 95 degrees ASAP as the box is designed to operate at 95 - 105 degrees C. It is a thought through decision by Ford and many other manufacturers that has pros and cons.

The pro is that to be honest the cooling capacity of the engine radiator is more than adequate for normal transmission usage.

1st con is that the seal on these heat exchanges fail and goodbye transmission friction plates and valve body seals etc

2nd con is that when under heavy loads like towing a 2 ton trailer the tranny gets warm despite the radiator which is more a function of water flow over the small exchanger.

Those 2 cons are enough reason people opt for an external oil cooler. Heck I have even mounted a switched 10" fan in front of my 11 row external cooler so that on 50 degree hot days (65+ deg tar temps ) I don't cook the tranny towing. I also have a 50mm thick engine radiator but I am crazy.

In the FG's with a ZF box there is a thermostat in the oil to water transfer block to control the temperature rise even tighter, as in zero cooling until about 80 degrees. Personally I hate those things as they do fail and let oil + water mix so goodbye to $4k for a ZF tranny rebuild. Even DIY it is about $1800 in parts.

I have been strongly thinking to resolve the temperature warming issue of the box by installing a external oil filter kit with integrated thermostat. The sandwich part usually start opening up at 75 degrees but apparently there is an 80 deg option available. I also like the idea of having an extra inline oil filter. Cost about $80 all up for the adapter and thermo sandwich on fleabay.


2. Your idea of just that simple metal tube being enough to air cool the transmission oil will be a costly theory to test. You might get away with it during winter and light driving.