This looks SERIOUS...should I replace OEM radiator...
From an Edmonds forum...
"
I have two 4runners both 1999 Limited model. For all those who own it, this is just a warning and you should check with your mechanic to confirm this.
About two months ago my transmission broke due to faulty design on the radiator connection. Supposedly Toyota made a line that connects the transmission with the radiator out of aluminum but they used a fitting out of metal which over time corrodes and caused the radiator fluid to mix with the transmission fluid. This will create huge problem and you will not notice it until your transmission will start to act weird and after a while your engine will overheat (coast to fix is about $2200 + if this happens)
The easy fix to it is to replace the radiator which will cost from $220 to $280.
I’m doing this in my second truck just to prevent the same problem and to avoid spending $2200 for new transmission.
I also spoke with couple of the Toyota mechanics and they told me that in the past few months they have seen several 1999 models with the radiator and trans fluid mixed.
They said that they contacted Toyota and advised them of the problem with this faulty design, but the response they got was that this is an old vehicle and warranty is long gone."
Also, in a related link in the Tundra Trucks forum...
trans cooler failure
There is a long thread here
http://www.yotatech.com/f2/bypass-oe...cooler-126953/
There are so many fail safe redundancies in a modern power train, so a known and increasingly occurring metallurgical design fault in the dual purpose radiator that can ruin both the engine AND transmission in a matter of minutes should warrant some notification from the manufacturer.
Informing owners of models are affected, and what recommended remedial action on this matter is needed. I love my Toyota, but silence here is not good.