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SMOD Question


zonianbrat
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Question about SMOD.

 

Hi all I have a question for you guru's. Can you tell me where the failure is happening exactly? I assume that the fluid runs through the radiator to get warm??? Is this correct? then it runs through a cooler? I'm a bit confused I guess. Would a replacement radiator solve this problem completely? I do not want to simply bypass as I tow a camper and want the tranny to stay cool. If I get a B&M tranny cooler do I simply block off the lines that go into the radiator? I want this done correctly and will be doing it myself so I want to be as knowledgible on the subject as possible before I start. I have done some searches and always seem to come back to the bypass threads. So I figured I would just straight up ask so maybe someone can explain it all to me rather than looking at other forums. Thank you all in advance. Oh and the vehicle is a 2007 R51

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I've read speculation that the cooler in the rad helps bring the tranny fluid up to temp more quickly on cold days, but I've never heard of someone losing a transmission from it being too cold.

 

The cooler in the radiator is supposed to transfer heat between the tranny fluid and the coolant. The problem is that the little tube or whatever's in there cracks and transfers coolant into the ATF, causing the strawberry milkshake of death. You could replace the radiator, if you trust that the new one is designed better and won't suffer the same fault. I think most people just unhook the trans lines from the radiator and hook them to an aftermarket cooler instead. (Probably best for towing anyway.) I don't know if blocking off the lines to the stock cooler would be necessary or worthwhile.

IIRC the reason they call it a bypass is that some R51s come with a real tranny cooler plumbed in line with the one in the radiator; with that setup, you can bypass the cooler in the radiator and still have the other one. Whether that cooler is enough to tow a camper is not a question I can answer.

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Thanks, for clearing that up a bit. I do have the auxillary cooler in front of the radiator. I talked to a dealership today and they recommended a new radiator and told me it is redesigned. They wanted to charge me 800 bucks total. Is a radiator hard to install in these R51's? I've done it on past vehicles and it wasnt much of a problem. If not I will just bypass the one I have. I seen one write-up but I will have to do more research as to make sure I dont screw anything up.

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For eight times the price of an aftermarket radiator, it had better be hard to install. :blink:

I completely agree. I just wasnt sure if it didnt involve something taking apart the front of the engine or something else stupid. I see this kind of thing more and more.

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Here is my writeup on how to bypass the radiator...

 

http://www.nissanpathfinders.net/forum/topic/37931-r51-owners-how-to-save-your-transmission/

 

Im not really sure why nissan decided to run the oil through the trans then through a seperate cooler. I can only assume for warming up the transmission fluid faster to soften shifts. I have done this bypass on several rigs now with no issues. If it wasnt stated, the radiators develop a small crack in the lower tank which is where the transmission fluid passes through. The pressure of the cooling system causes coolant to get into the transmission fluid system and will destroy the clutches in the transmission. This happened to me personally when I was going to work one day in my buddies Frontier. It failed and we were stuck on the side of the road. Nissan had not extened the warranty yet and he was basicly screwed(even though he worked at the Infiniti dealer with me and nissan didnt care!). Somehow they ok'd replacing his transmission, but not the radiator. They basicly made him buy a facotry radiator then they would put the transmission in. About 6 months later the warranty extension came out and he got refunded by Nissan.

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e30c4af416b9a7bd9a0f0f4df2afc817.jpg

 

So to be sure. I put long hose end #1 where the #2 hose is currently in the pic. Then I put #2 hose where #1 was originally? Sorry but I'm going to do this today and want to be sure. I will follow where the hoses go for confirmation but it also helps to know what your going to be doing ahead of time then visually verifying it.

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