Nissan Maxima QX auto transmission

I have a 2002 Nissan Maxima QX SE Plus 3.0 Auto (A33 Series - and please note this is a UK car, not american, in case it makes a difference) that is
currently experiencing cooling problems. The garage found the radiator to be blocked and have a new rad on order.
At the bottom of the rad, and integral to it, is an oil cooler pipe for the automatic transmission. When the mechanic disconnected the pipes to lift out the rad he expected a certain amount of oil to come out but they were dry - and I do mean bone dry. No oil has been anywhere near those pipes for a long time, he reckoned. He said that he's come across situations where the oil cooler pipe in the rad has been leaking so the pipes from the auto box have just been joined together effectively bypassing the cooler pipe, but that wasn't the case here. The pipe in the rad has not been blocked in any way as he could/can blow air through it (and no oil came out then either).
So to my question:
Is there some sort of valve within the automatic transmission that only opens when the fluid gets hot enough to need cooling down, and in this case it's just never been hot enough to need diverting to the cooler, or should there be a permanent flow of fluid from the gearbox to the cooler and back again?
I should say that I've had the car for two years, it drives like a dream and I've never noticed a problem with the auto box at all, apart from over the last 6 months I've noticed downshifts becoming _slightly_ jerkier and when going from neutral to drive there's a _slightly_ harsher jerk than there used to be, but these really are very small changes from normal. ATF fluid level is normal and no colour change.
This really would not have come to light if it had not been necessary to remove the radiator but, now that it has, is it a problem?
TIA
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On 10/2/10 8:57 AM, in article snipped-for-privacy@bt.com,

Is he saying the pipes are connected to the trans or just left open?
I guess there is a chance the inlet is blocked in the transmission. You'ld have to drop the transmission pan to check it.
On some of the late '90s American Maximas & I30s that used the 3.0 (3.0 was not used in 2002, they were all 3.5), the trans oil cooler lines ran to a small loop of pipe that was mounted in front of the radiator and did not use the lines in the radiator. Any chance you have that arrangement?
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E. Meyer wrote:

Thanks for your reply. The pipes were definitely connected to the transmission and the oil cooler is definitely in the radiator rather than a loop of pipe in front of it. The pipes in question are marked as number 6 in this diagram
http://i137.photobucket.com/albums/q235/darkdoo/radiator.jpg
You mention dropping the transmission pan. Is that easy enough to do or does half the car have to be dismantled to get at it? :-)
Thanks again.
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On 10/2/10 11:45 AM, in article vvadnb7Xosw0 snipped-for-privacy@bt.com,

The A/T pan is cleanly accessible on the US models. I assume the European model will be similar. You might also check the forums at maxima.org & see if anybody knows anything.
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E. Meyer wrote:

Thank you very much my friend, will do.
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