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Discussion Starter · #1 ·
I have a 2008 Xterra S 4x4 with 59,000 miles on it.

If I plan on keeping the truck past 80,000 where the extended radiator warranty expires, instead of doing the bypass, I've heard of the radiator just being replaced as a preventative measure.

I've read through several pages on this topic, and I suppose I'm still a little confused. What part exactly breaks to cause this issue?

Is it the main radiator or the trans cooler.

Would the main engine radiator need to be replaced or just the trans cooler? or both?

I believe my confusion stems from many people referring to the trans cooler as the "radiator"

Rich
 

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Something inside the radiator itself causes the transmission fluid and rad fluid to mix, which is very bad for the transmission. Replacing the radiator should alleviate the problem. Some people think the original tranny fluid was corrosive and caused the problem. They switched to a different fluid in 2008 or 2009 which is when the problem stopped occurring I believe.
 

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Discussion Starter · #3 ·
Thanks.

I guess I always assumed it was the trans cooler. Why does the trans fluid go through the engine radiator at all if the trans cooler is there?
 

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The stand-alone trans cooler is an air-to-fluid cooler, the in-rad trans cooler is a fluid-to-fluid cooler and is much more efficient than the air-to-fluid cooler ... in fact, the bulk of trans fluid cooling happens in the bottom of the radiator, as the fluid moves through the in-rad cooler.

jeff_redx put together an awesome post that details the whole combined engine and AT cooling system, and how it functions together as a unit, here: http://www.thenewx.org/forum/showthread.php?t=65980 ... it's probably something you've already read, but in case you haven't, it's worth studying (and in case folks who are reading this haven't seen it, it bears linking).

The part that fails in the early model radiators (I believe), is a weld that's internal to the unit ... where one of the trans fluid lines joins the in-rad trans cooler, but is internal to the radiator itself. This then exposes the two working fluids to the possibility of cross-contamination.
 

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Main trans. fluid cooler is in radiator - we also have separate Aux. cooler. Problem is with main cooler (most auto tranny cars and trucks forever have used tran. fluid cooler in rad.). Nissan has extended some warranty help thru model year '10 - but they have not and surely will not release statistical info on susceptibility. From reading here and on Frontiers, seems like few reports of problems with late '08 and later models. Worry free fix is to replace radiator.
 

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Has it be confirmed that most or all aftermarket radiators are free from this defect? My 2006 is still running the original radiator after 107,000 miles, but it has been bypassed for the past two years. If I was to replace the radiator with an aftermarket radiator and reverse the bypass, would I be safe? Have there be any reports of the aftermarket units failing?


Thanks,
Zack
 
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