Just a word here to you folks doing the transmission radiator cooler bypass. DON'T! Water cools about 32x's better and faster than air. The transmission fluid coming from the torque converter to the radiator is at a much higher temperature than the coolant in the radiator. Once the transmission fluid gets to the radiator, it is quickly cooled down to the cooling system temperature. Then it goes to the auxilliary cooler where it gets cooled below cooling system temperature. If you tow, haul or off road, put a second auxiliiary cooler in series with what you have now, or just get a bigger auxilliary trans cooler. It can't be too big, or your return flow rate will drop. If your concerned about cross contamination, get a good aftermarket radiator and rest easy. HEAT is an automatic transmissions worst enemy.
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idk if you will be recieving many "thank you's" for this
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In no way am I trying to be an a** this is just my experience… I did the bypass a week ago. I have an aftermarket trans temp gauge that’s hooked up to the test port. Prior to the mod I was running between 150 and 180 on normal driving. With a trailer I jumped as high as 240. After the mod I’m running between 140 and 160, with the trailer the highest I’ve seen is 210.
I know there’s a ton of variables involved... however the outside temp, roads traveled and load on my truck have been pretty consistent. I have noticed that the transmission fluid cools much quicker when it gets up high then it did before the mod.
Like I said it’s not 100 % a controlled experiment but it’s good enough in my opinion to keep it moded. I forgot to mention I have just the stock cooler, and 100% new fluid 2k ago.
On a side note... I know that fluids cool much quicker in liquid. However, the fluid goes through the radiator at a pretty quick rate. When I replaced my fluid I disconnected trans cooler return line and ran it in to a 5 gallon bucket. I started the truck and dumped the new fluid in to the pan while the old stuff pumped in to the bucket. This was the closest thing I could come up with to get 100 % of the fluid replaced without flushing it at the dealer. I marked each quart line on the bucket so I knew what rate to dump the new fluid at. Muchto my amazement I pumped out 15 qt's in about 60 seconds with the truck in park. I was dumping it in as fast as I could and I barely kept up with it... My point being, I don’t think the fluid sticks around inside the raditaor long enough to make a huge difference. There is only about 1/2 cup total that’s in there at any given time.
Also I talked to a master tech at nissan about putting a bigger cooler in there because of the towing I do. I was concerned about the pressure also. He told me I could go as big as I wanted on a secondary cooler. It really doesnt matter because after it leaves the cooler it dumps back in to the pan. The cooler is the end of the line so just make sure there is enough fluid to fill everything
Just my 2 cents...
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07 4x4 King cab
Last edited by Kort; 05-17-2010 at 01:52 AM.
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Just a word here to you folks doing the transmission radiator cooler bypass. DON'T! Water cools about 32x's better and faster than air. The transmission fluid coming from the torque converter to the radiator is at a much higher temperature than the coolant in the radiator. Once the transmission fluid gets to the radiator, it is quickly cooled down to the cooling system temperature. Then it goes to the auxilliary cooler where it gets cooled below cooling system temperature. If you tow, haul or off road, put a second auxiliiary cooler in series with what you have now, or just get a bigger auxilliary trans cooler. It can't be too big, or your return flow rate will drop. If your concerned about cross contamination, get a good aftermarket radiator and rest easy. HEAT is an automatic transmissions worst enemy.
I don't build the trucks. The engineers who design and spec the vehicles are knowledgeable enough to know what particular systems need to have to be effective. The science doesn't fail, the components do.
I don't build the trucks. The engineers who design and spec the vehicles are knowledgeable enough to know what particular systems need to have to be effective. The science doesn't fail, the components do.
I dont want that component to be my transmission from cross contamination. I completely see your point and understand where your coming from. But as the post above said, its kind of an up hill battle
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07 4x4 King cab
Last edited by Kort; 05-17-2010 at 05:08 AM.
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I don't build the trucks. The engineers who design and spec the vehicles are knowledgeable enough to know what particular systems need to have to be effective. The science doesn't fail, the components do.
That's why they put in the large cooler behind the grille. Every automatic transmission will have the standard radiator cooler from the factory. When you plan on towing heavy loads, you will always be better off with an auxiliary cooler to keep the fluid temperature down and protect the transmission.
That's why they put in the large cooler behind the grille. Every automatic transmission will have the standard radiator cooler from the factory. When you plan on towing heavy loads, you will always be better off with an auxiliary cooler to keep the fluid temperature down and protect the transmission.
The issue was about not bypassing the radiator trans cooler. Yes you are correct Zero, to a point, but the auxilliary cooler is secondary. It is by no means a replacement for the primary radiator trans cooler. Even if you run two aux coolers, and no rad cooler. The aux and rad trans coolers have to be in series, and work in tandem. Now the size of the aux cooler can be changed, to accomodate the work load. Otherwise your just slowly cooking your own transmission. I'm just trying to warn people, and not lay blame or scorn on anyone. I work hard for my money, and it pays for my truck. Why would I destroy something I work hard to attain? Also, why would you, or anyone else for that matter. The cross contamination issue can simply be addressed by replacing the OEM radiator with a quality aftermarket radiator. Think about it, whats $200.00 for a radiator vs $3,000.00 for a transmission? That's all I'm saying.
I dont want that component to be my transmission from cross contamination. I completely see your point and understand where your coming from. But as the post above said, its kind of an up hill battle
The cross contamination issue comes about due to the fact that the OEM radiator seal fails, that seperates the trans fluid from the cooling system. Whether the system fails due to a faulty manufacturing process, or epoxy or weld is something Nissan should have addressed at that time. The problem can simply be resolved by replacing the OEM radiator, with one of a known good quality. There's been alot of horror stories here about that issue. Unfortunately, Nissan won't stand behind it.
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