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Radiator Bypassed - Transmission Fluid

57K views 60 replies 18 participants last post by  BlingAlong06 
#1 ·
I've been wanting to do this for awhile and finally did it on Saturday. I wanted to wait until I did some "real world driving" to see the impact before I posted up the thread and I have to say, so far, I'm impressed. I wish I had something other than the OEM gauge for exact numbers, but it's visibly different.

Normal, in town driving, the OEM gauge would run a little over half and now it's under half (just before the "gear")...where I was shocked was on the highway (60-70 MPH and it's about 80 degrees out) this morning into work. Before, it would always run halfway, but on my 30 minute trek down the highway it barely broke 1/4 of the way the whole time.

Anyway, on to what I did.

I purchased the Hayden Rapid Cool Transmission Cooler from my local Autozone and 10' of hose. I got the one that was made for vehicles that tow over 10k lbs, don't remember the exact model number but I believe it was this one:

Compressor Works/Transmission Oil Cooler (911678) | AutoZone.com

For the install because it is a little large, I had to be a little creative.

1. Removed the grill, horn, and front fan to give me a little room to move.
2. I was able to slide it in and mount it to the back side of the bar that the lower part of the grill clips into using wire ties, so essentially, it would sit between the fan and the AC
3. Removed the assembly on the passenger side of the radiator that runs from the lower portion of the radiator up into the OEM cooler
4. The metal tube that runs up the passenger side of the radiator, I wanted to reuse on the drivers side since it's no longer needed and I don't want the rubber transmission line getting crushed, so I slid it up along the drivers side of the radiator in between the radiator and the plastic casing. Make sure you cover the ends because you don't want dirt getting in the tube.
5. I cut a new length of tube to run from the transmission outlet to the bottom part of the metal tube I just slid up the side of the radiator and fastened it together.
6. The Hayden cooler has larger inlets than the OEM tube so I used the larger tube that came with the kit to run from the top of the metal tube on the drivers side into the transmission cooler.
7. I then ran the larger tube from the outlet on the Hayden into the OEM Transmission cooler.
8. From there, everything else remains the same.
9. Tightened everything down and reinstalled the fan and the horns
10. Capped the inlet and outlet on the bottom of the radiator and started the truck to check for leaks
11. Reinstalled the grill and went for a cruise :thumbsup:

Here are a couple pics that I took:

This is where the cooler is installed


This is the inlet on the drivers side, you can see the top of the metal tube that I reused from the passengers side of the radiator


This is the tube from the outlet on the Hayden into the OEM Transmission cooler


Here is the underside of the truck. I didn't think to snap the pictures until after I soaked the bottom with Simple Green and hosed it off :lol:



Unfortunately, I didn't take pictures all the way through the process, but if any of the steps are unclear, feel free to hit me up.
 

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#2 ·
Was this because you thought it was needed or because of the past radiator failures?
 
#3 ·
Past radiator failures...plus I saw a couple fresh drips of transmission fluid on the lower radiator shroud and don't know if something happened to the new CSF I just put in a couple thousand miles ago.

Even if it wasn't, I wasn't taking the chance of blowing another one. Part of me thinks that for some reason, my transmission fluid pressure is up. Robkar mentioned that the BD Performance Tune increases the pressure, but I haven't had the BDGT on in over 10k miles, so maybe when you go back to stock it doesn't reset that setting? :dunno:

Either way, the decreased temps are never a bad thing.
 
#4 ·
What was the cost for this? I'm going to install my CSF in a couple of weeks and am considering doing this while I do the radiator install?
 
#5 ·
The cooler was $60 and 10 feet of hose was just under $20, and that should be enough for you to do this and replace all lines. If you want to do it, it would definitely be easier when you have the whole front end apart anyway.
 
#6 ·
I'm going to bookmark this page. Thanx bills.
 
#9 ·
I am getting some kind of leak myself. Not major, but cant really tell what it is. I took off my skid plate/pan and cleaned the lower front of my motor yesterday. First...Is it ok to run a while without this pan (mostly highway/secondary roads)?

I am seriously considering ordering the CST and a cooler, maybe this one. Can you post more pics of your cooling setup? Maybe with flags for I.D.? I am quite experienced mechanically, but have spent very little time with a Titan, any help would be greatly appreciated.

I am looking for longevity and a little more power/economy. DTLT are in my near future, with UPREV. I plan on putting 250-300k miles on this thing in the next 4 years, I average ~60k/year now. I may decide to buy a mileage whore and save the T, but that will eliminate mod money.

Thoughts. (BTW, unintentional hijack, please feel free to answer coolant relevant questions here, and any other advice via PM)

Thanks!
 
#10 ·
I am getting some kind of leak myself. Not major, but cant really tell what it is. I took off my skid plate/pan and cleaned the lower front of my motor yesterday. First...Is it ok to run a while without this pan (mostly highway/secondary roads)?
It's fine to run without the skid plate. Not sure if you've seen the threads with the issues around cooling that I've had, but I'm on my third radiator in 10k miles. When the second one cracked it was similar to the what you're describing. It was a slow leak of transmission fluid that was getting splattered on the underside of the truck. When I pulled the radiator, the whole bottom corner of the fins in the front of the radiator was covered in transmission fluid.

I am seriously considering ordering the CST and a cooler, maybe this one. Can you post more pics of your cooling setup? Maybe with flags for I.D.? I am quite experienced mechanically, but have spent very little time with a Titan, any help would be greatly appreciated.
I can take some more pics later and tag them, but for the radiator replacement itself, there is a great thread on here that was what I followed on here when I replaced the first radiator.

I'm now running the CSF radiator and bypassed the lower portion for transmission fluid and it's being routed through this new cooler instead.

I am looking for longevity and a little more power/economy. DTLT are in my near future, with UPREV. I plan on putting 250-300k miles on this thing in the next 4 years, I average ~60k/year now. I may decide to buy a mileage whore and save the T, but that will eliminate mod money.

Thoughts. (BTW, unintentional hijack, please feel free to answer coolant relevant questions here, and any other advice via PM)

Thanks!
I'm in the same boat, I want to run this truck for a long time...I'm looking to have it paid off soon and once it is, it'll be used for towing my boat and weekend use. I'll probably buy a 370 for everyday use.
 
#11 ·
I just finished this mod about a week ago, with the Hayden Rapid-cool 679.. I just got done towing a 6000 pound boat to and from Lake Havasu, from LA... The hottest my transmission ever got was 150* while going up the Cajon Pass on the I15, doing 65mph the whole way up. (BDGT specs)

Last year during the same trip, I was seeing temps in excess of 180* while climbing this grade.

The only difference in my install vs yours is that I ran mine in series with the coolers already on the truck instead of bypassing it. What are the cons & pros of having it my way vs yours?
 
#12 ·
I kept the OEM transmission cooler so the pro with doing it your way would be keeping a third cooler being the radiator.

The con would be my main reason for doing it like this and that's running it through the radiator. I didn't want my transmission fluid running through the radiator any longer because of all the issues I've had.
 
#13 ·
Nice Mod Bill! Look's to be a little bit larger than the cooler i have:

Long Tru-Cool LPD Cooler SR4588
Medium Duty Driving, full size cars
GVW Rating - 19,000 lbs.
BTU Rating - 14,400 btu.
11/32" Hose Barb
 
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#14 ·
Thanks man, it was a tight fit getting it behind the bar...I got a little nervous at first, but after I removed the fan, I was able to get it in from the bottom.
 
#15 ·
I wonder if there will be an issue with this setup in cold weather? Not for Delray Beach but for colder weather areas.
 
#16 ·
Not sure why there would be, just keep the temps even cooler...just replacing the radiator cooling mechanism with another...
 
#21 ·
Possibly, I know the fluid starts flowing as soon as you start it up.
 
#23 ·
That's the one. I don't know how much transmission fluid you need.
 
#25 ·
There were 2 questions there and I should have added a little more.

My first question was to check your new radiator and the fit with the new transmission cooler. <-- OK I got that one.

Question #2 was on the transmission fluid cooler and after adding the after market cooler, how much more fluid you added .. ;)
 
#26 ·
Oh, sorry :lol:

It was minimal, it only took about quarter of a quart with the new cooler and what I lost installing it.
 
#27 ·
It seems to me that this would be a very good time to change the transmission fluid as well.

After checking with Amsoil, they recommend: Synthetic Multi-Vehicle Automatic Transmission Fluid (ATFQT)
 
#28 ·
I found a better deal on the CFS Radiator at Parts Train ...
Order placed, to bad there was tax ....
Now I just need to find the tranny cooler.

 

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#29 ·
#30 ·
I think for those of us in colder areas this still wont be a big issue, maybe just let it idle for a few minutes before you leave. The TC generates a lot of heat anyways plus this is saving your radiator lol. But if you're going away from the factory setup I would suggest installing a trans temp gauge that reads numbers! lol.
 
#31 ·
I have to say, from a temp perspective, this has exceeded my expectations. I really wasn't expecting huge temp improvements, I was just going to be happy if everything stayed the same and I simply bypassed the radiator.

Unfortunately, the only thing I have to go on is visually with the gauge, but before I did this, the tranny temp gauge was dead center.

Now for hard city driving, it's just below half and when I'm driving on the highway and getting the higher airflow through the grill, it's just over quarter.
 
#32 ·
Just an update, I towed my boat for the first time with this setup today and the temp still stayed below the halfway mark...previously, it would run at or a little above half.
 
#33 ·
thanks bills.
I'm going to be doing this mod as soon as i can get the parts, btwn towing the boat on super hot days, I've seen my trans gauge go higher then I would have liked. for 80bucks and a few hours is defiantly worth the effort in my opinion.
Anybody know of any tuner or way to firm up the shifts on the trans?? I find it shifts great/ firm when cold in the morning, but sometimes it seems to just miss shift..maybe it has something to do with 160k of abuse lol thanks again
 
#34 ·
#44 ·
i see... i like... i buy lol

Lucky for me being in Canada I get the parts shipped to Niagara and drive em over the border :) did you see that the cover is on sale for $35!! :eyebrow:
 
#35 · (Edited)
I just ordered the Hayden 678 for $56.37 shipped from Amazon which is the one that is 11" x 9.5" x 3/4" which is the same as the Autozone version installed by bills. The Hayden 679 is 11" x 11.625" x 3/4". I figured the 678 will be fine for me since it lowers the ATF temp vs stock when towing a boat in Florida.

Edit: Just changed order to Hayden 679 based on bills comment that he got the one rated for over 10,000 lbs. I think that is the 679, not the 678.

The bypass thread at the Frontier forum raised the issue of liquid/liquid (stock ATF cooler in radiator) vs liquid/air (aftermarket ATF cooler) as being a possible issue since the liquid/liquid heat exchanger transfers more heat, I think somebody posted that it was a 30 x factor. But nobody did the math to account for the fact that the antifreeze in the radiator is at 170 F vs an air temp of say 90 F max and that the aftermarket cooler has a larger surface area. I think the quantity of heat transferred is proportional to the surface area and the temperature differential between the fluid to be cooled and the cooling fluid. So you have liquid/170 F liquid (smaller surface area) vs. liquid/90 F air (bigger surface area). This seems to be confirmed by the empirical evidence that it results in lower ATF temps measured by the stock temp gauge.

The other issue is cold weather warming to operating temps, and I guess I will wait and see on that as I have not seen any posts that it created a problem.
 
#36 ·
The bypass thread at the Frontier forum raised the issue of liquid/liquid (stock ATF cooler in radiator) vs liquid/air (aftermarket ATF cooler) as being a possible issue since the liquid/liquid heat exchanger transfers more heat, I think somebody posted that it was a 30 x factor. But nobody did the math to account for the fact that the antifreeze in the radiator is at 170 F vs an air temp of say 90 F max and that the aftermarket cooler has a larger surface area. I think the quantity of heat transferred is proportional to the surface area and the temperature differential between the fluid to be cooled and the cooling fluid. So you have liquid/170 F liquid (smaller surface area) vs. liquid/90 F air (bigger surface area). This seems to be confirmed by the empirical evidence that it results in lower ATF temps measured by the stock temp gauge.
.
When I read that part of the thread, I had to laugh a little. You are correct that it was forgotten about the 170/180 water temp. Also the number they put out with the 30X BTU drop was for direct liquid contact cooling, and not thought a heat exchanger... ;)
 
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#37 ·
Just did mine - thx to this thread.. got it @ Oreilly Auto Parts for about 50 bucks. Not bad IMO..



Im rolling like this right now - need to find something to plug these up.



Take note that Im in texas so we dont get much winter and the summers are KILLER.. This is after about 20 mins of driving in 90º heat..:)

 
#38 ·
Jake, for the bottom of the radiator, I just took extra hose I had and connected the intake an out together.
 
#39 ·
I lost the tranny in my 06 Xterra due to a defective radiator. First indications were the rumble strip like vibrations coming from it when the vehicle would try to shift into overdrive.

I bypassed the radiator and flushed 20 quarts of new fluid through the tranny, and everything was back to normal for about a month. Then it went out. $3500 to rebuild it and install aux tranny cooler.

I called the dealer where I had purchased both the X and my Frontier, and they reccomended doing the bypass on the Frontier also.

I don't have such a high opinion of Nissan now due to the way they have handled the situation with the radiators. Increasing the warranty on the radiators to 80k is a pathetic fix. Having the dealers tell the customers to re-engineer the truck themselves is pretty lame.
 
#41 ·
BAC, I'm sure those would be fine with a clamp. I just used the hose because I had a bunch of it laying around.
 
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