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Discussion Starter · #1 ·
Hey guys! Been on here for a while now, such a great source of information! Never posted though but now I figured I'd actually get some help as I cannot find the answer outright.

I have an '06 OR with 121k and am just now hearing about SMOD. Luckily, I don't have any of the symptoms yet, no vibrations when the X shifts into overdrive and no foam on the radiator cap and coolant is still green!

BUT here is my question (which may be obvious but I couldn't find the answer to, so sorry if this is a stupid question), by doing the bypass, will I still be running the factory external tranny cooler? or does it bypass the radiator and cooler all together? If so how can I re route it to run the factory tranny cooler? I tow quite frequently, (small boat, small car, 2 jet skis, or a small-ish covered trailer) also the summers where I live get over 105 degrees so the external cooler is pretty important.

Thanks for you input (and forgiving my ignorance)!!
 

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Discussion Starter · #3 ·
Okay cool, thank you! So tomorrow I will have the radiator and transmission flushed, if the problem is with the old ATF being corrosive, do I still need to do the bypass if it has new ATF and new coolant?
 

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Okay cool, thank you! So tomorrow I will have the radiator and transmission flushed, if the problem is with the old ATF being corrosive, do I still need to do the bypass if it has new ATF and new coolant?
Yes. Its had plenty of years already (7..) to start corroding away. Who knows how thin the walls on the heat exchanger are now...
 

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Discussion Starter · #5 ·
Would replacing the radiator fix the problem as well, since it will have non corrosive ATF? in theory, it shouldn't have the deterioration problem like before right? I was thinking about putting a new rad in anyway soon, I would like to keep the X as close to stock as possible when it comes to the cooling and what not. Thanks for you help!
 

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Less work and $$ to do the bypass and add an aftermarket cooler while retaining the stock cooler which is in front of the radiator.
 

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Discussion Starter · #7 ·
Yeah but to be honest I would really just rather keep the OEM configuration and avoid the situation so if I can do that just by replacing the radiator (which will need replaced at some point anyway) I'd like to do that I think.
 

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If you go that route you may want to use the Matic S fluid as it is the newest version. It should be backwards compatible


Yeah but to be honest I would really just rather keep the OEM configuration and avoid the situation so if I can do that just by replacing the radiator (which will need replaced at some point anyway) I'd like to do that I think.
 

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I got a new radiator installed under the extended factory warrenty but was wondering what people think about the new radiators from Nissan? Is it safe w/o doing the bypass on the new radiators?
 

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SMOD concerns

So i know this has been covered in detail but i have a specific question in regards to my 06 X. Lately i had a problem with my heating unit and found a cracked radiator. After doing some research is when i read about teh S.M.O.D. I do not have signs of the SMOD as of now nor have i done teh bypass yet. I have about 110k miles on it.

I just had the radiator replaced since it was cracked and i am wondering if i need to do a tranny flush and replace with the s matic fluid right now as well (instead of doing the bypass) if i need to at all with the new radiator.

I asked my local mechanic about the scenario and he said he has noticed no mixing of coolant and tranny fluid, and when he replaced the radiator he did not do teh tranny flush and replace with Matic S fluid. Do these things need to go hand in hand. should i tell him to go ahead and do the tranny flush and add the new matic s fluid since from what i have read is the J fluid is one of the main cuplrits in eating away at the tranny which is what causing the mixing in teh radiator and tranny?

Or since the new radiator has been replaced does this cover the need for the tranny flush and S fluid and Bypass?
 

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i recommend replacing the radiator with a good aftermarket model then flushing the trans MANUALLY. The PMF. Not a machine!

Replace matic j with matic s!!!!
 

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OK guys I've read thru this several times (and other threads) and gotta say I just don't get. I'm reasonably intelligent but somehow am missing something. I get that the (large) radiator is for engine cooling and the (small) cooler is for transmission cooling. I also follow the bypass procedure but don't understand how that still leaves the cooler "in play" or how if it is still "in play" why a secondary cooler is recommended in extreme conditions.
Maybe what I'm not understanding is the relationship between the radiator and the cooler. Does the cooler circulate transmission fluid from the tranny or radiator fluid from the radiator? If the answer is tranny fluid then it seems the bypass takes the cooler "out of play".
Also, just exactly how and where is it the system fails and allows the two fluids to mix? At the cooler, at the radiator, or at the transmission?
When someone states they changed the radiator the bypass and secondary cooler aren't needed (with proper S fluid). But if the bypass is made and secondary cooler installed the radiator is not an issue.
Hopefully someone reading thru this can see where I'm confused and help me out here.
BTW just got a new to me 2008 Off Road model w/82k so trying to understand what I need to do. I understand this is mostly a 2005 - 2007 issue but there seems to be different years quoted in different threads?
Thanks for any help here.
 

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OK guys I've read thru this several times (and other threads) and gotta say I just don't get. I'm reasonably intelligent but somehow am missing something. I get that the (large) radiator is for engine cooling and the (small) cooler is for transmission cooling. I also follow the bypass procedure but don't understand how that still leaves the cooler "in play" or how if it is still "in play" why a secondary cooler is recommended in extreme conditions.
Maybe what I'm not understanding is the relationship between the radiator and the cooler. Does the cooler circulate transmission fluid from the tranny or radiator fluid from the radiator? If the answer is tranny fluid then it seems the bypass takes the cooler "out of play".
Also, just exactly how and where is it the system fails and allows the two fluids to mix? At the cooler, at the radiator, or at the transmission?
When someone states they changed the radiator the bypass and secondary cooler aren't needed (with proper S fluid). But if the bypass is made and secondary cooler installed the radiator is not an issue.
Hopefully someone reading thru this can see where I'm confused and help me out here.
BTW just got a new to me 2008 Off Road model w/82k so trying to understand what I need to do. I understand this is mostly a 2005 - 2007 issue but there seems to be different years quoted in different threads?
Thanks for any help here.
Trans fluid runs from the tranny through the bottom of the radiator contained in its own tube then out of the radiator and through the external trans cooler that is in front of the radiator then back into the trans. The tube that runs through the bottom of the radiator can deteriorate after time letting trans fluid mix with coolant and vice versa.

Sent from my SGH-M919
 

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With the bypass you are skipping the tube that runs through the radiator and only using the external trans cooler. To some extent the tube that runs through the radiator can help cool the trans fluid so some like to add another external cooler to make up for that. I just put a fan on my stock external trans cooler and turn it on when needed which is rarely. I monitor trans temps with a bullydog tuner.

Sent from my SGH-M919
 

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Got it, thanks. That seems like an odd arrangement but makes sense to me now. Do I need to be concerned with a 2008 model? If so could a temp controlled fan be put on the cooler instead of being manually switched?
 
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