Write-Up: Transmission Cooler Install

Yes Automotive is 45* and AN is 37* flare.
Definitely need different flaring tools for each.

Aaron do you have the tubing ends and flare nut fittings you had to cut off at the radiator, that you can ship to me so I can try and pre-make some hard lines along with some 11/32" hose.
If you could mail me them I would be greatly appreciative and naturally pay you for shipping.

I can then post up all the necessary adapters to go from Automotive flair nut to possible AN fittings, etc.

I also have one question for you; why didn't you just eliminate the cooler in the radiator and just use your aftermarket cooler by itself.?
It seems to me it would have made the job much easier with less connections and since you have a 180* thermostat in line you would be OK.
Yes / No.........

AA wrote:

Yes, mine has flared lines going into the radiator. I wonder if this adapter would fit? Link

You don't have any NPT fittings in the system to adapt.
NPT=National Pipe Thread, which is a tapered thread.
This type of thread is not used in a Flare Nut installation.

I did not cut the lines, or else I would have a much easier time identifying the fittings!

If you look in this picture, you can see how I tapped into the radiator and the existing flared line:

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why didn't you just eliminate the cooler in the radiator and just use your aftermarket cooler by itself.? It seems to me it would have made the job much easier with less connections and since you have a 180* thermostat in line you would be OK.

Two reasons:

1) two coolers provide more cooling efficiency than only one. Why waste the OEM cooling that's build into the car?

2) bypassing the OEM cooler (radiator) would require removing both trans lines, whereas running both coolers in series only requires removing the top line. It uses two connections either way, except the bottom line is much harder to access, requiring removal of the bottom air deflector and both radiator fans.

It's more difficult to bypass the radiator than to include it. The reason it took me so long is that I actually installed my cooler twice, once from the bottom line, and again from the top line.

The way the thermal bypass works, it makes no difference whether you bypass the OEM radiator or include it. You use the same number of hoses and same number of connections regardless.

O.K. I understand a little better what you went through to accomplish the job. ( I have been reading the previous posts more carefully and re-reading.) I still can not tell from the pic above that you left the OEM line in the Radiator. I thought you removed the line, installed a barbed fitting, cut the OEM end of the metal tube with flare nut fitting off and used one of the fittings you bought to attach the new hose to the OEM Steel Tube (a compression fitting with ferrule, as would be used in a brake system), that would have left that one OEM tube end with threaded flared fitting available.
But now that you have identified the Radiator fittings as 5/16" Automotive Flair Tube fittings, I'll be able to work with that.
I personally will probably eliminate the radiator cooling tank as it is always at or above 180* during normal operation and is not needed unless you consider the pint or so of fluid to be beneficial.
You don't necessarily need access to the lower radiator fitting to eliminate the radiator from the loop. Just cut the line where convenient and push it out of site.
Run all new line's, a combination of steel tubing and rubber hose rated for transmission duty, to the new oil cooler along with 180* thermostat.
I'm actually going to buy 2 of those thermostat's, one for the car and one for a bike i have with an oil cooler and no thermostat currently installed.
The motorcycle world of aftermarket product want's closer to $100.00 for a thermostat rated at the same temp and they are not serviceable like the one you showed us in the pic.
At least the $30.00 Trans thermostat can be disassembled and inspected now and then.

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I could not tell from that pic that you left the OEM line in the Radiator. I thought you removed the line, installed a barbed fitting, cut the OEM end of the metal tube with flare nut fitting off and used one of the fittings you bought to attach the new hose to the OEM Steel Tube, that would have left that one OEM tube end with threaded flared fitting available.

I left only the lower OEM line in the radiator. I removed the top line, but did not cut it. I did install a barb fitting in the top radiator port (you can see in pic). I used a female 5/16"-to-barb fitting to tap into the top (return) line (also in pic).

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But now that you have identified the Radiator fittings as 5/16" Automotive Flair Tube fittings, I'll be able to work with that.

I have not - you did, lol!

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I personally will probably eliminate the radiator cooling tank as it is always at or above 180* during normal operation and is not needed unless you consider the pint or so of fluid to be beneficial.

Of course, the extra fluid will help cool the system even more. Also, the radiator cooler offers extra BTUs of cooling that you won't have if you bypass it. The fluid coming out of the transmission is probably above 180º under heavy load, so the radiator is relatively cool in comparison.

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You don't necessarily need access to the lower radiator fitting to eliminate the radiator from the loop. Just cut the line where convenient and push it out of site.

The lower line is the supply line. You must somehow tap into it and route to your cooler. Either must remove from radiator,remove from transmission, or cut and flare in-line.

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Run all new line's, a combination of steel tubing and rubber hose rated for transmission duty, to the new oil cooler along with 180* thermostat.

This is a heck of a lot of work and $$$ to spend, considering the OEM lines are already there!

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I'm actually going to buy 2 of those thermostat's, one for the car and one for a bike i have with an oil cooler and no thermostat currently installed.

Understand, the function of the bypass is for using very large coolers in very cold weather. The problem is that many cars won't lock-up the TCC until they are above 100ºF. Large coolers can keep the temp below that point in freezing ambient temps. Otherwise, I don't see the need for a bypass, which requires four extra hose connections.

Rickw wrote:

Yes Automotive is 45* and AN is 37* flare.
Definitely need different flaring tools for each.

More importantly in this case, you can't connect one to the other.

Quote :

I also have one question for you; why didn't you just eliminate the cooler in the radiator and just use your aftermarket cooler by itself.?

Another reason is that in a place that gets cold, say Ohio, the stock cooler acts as a warmer, to get the tranny up to operating temperature sooner.


Now, I have a really stupid question: Despite looking at photos on Google, I can't see what the difference is between 'normal' and tapered threads... I understand that one is self-sealing, like NPT, while the other isn't, like when the flare is making the seal - I just don't see how/why.

I think normal threads are loose enough that they will allow fluid to pass through under pressure, while tapered threads form a seal as they are tightened:

AA wrote:

I think normal threads are loose enough that they will allow fluid to pass through under pressure, while tapered threads form a seal as they are tightened:

which is why on a flare nut fitting you are pressing the sealing base of the fitting onto a matching surface on the tube. You have straight threads to get the most force onto the sealing surfaces.

your drawing shows a straight thread going into a tapered hole btw.

I have my old radiator out of the car. I'll go try to make sense of it tonight.

AA wrote:

I think normal threads are loose enough that they will allow fluid to pass through under pressure, while tapered threads form a seal as they are tightened:

This may be true if you didn't have a flared tube and mating flared fitting to tighten it to.
That's why I said that there are situations where a NPT fitting is correct for the application and other times when the flared tube and fitting is correct for a different application, such as your transmission cooling tubes and brake tubing, etc. These applications where they are designed to hold fluid at high pressures require a flared tube fitting. It is identicle to the AN fitting except for the amount of degree's that the tube and fittings are flared to.
All Hydraulic lines, that I know of, use a flared tube or some other type of compression fitting.
Only in plumbing do you see NPT fittings
I don't claim to know all the engineering criteria that is needed to determine which will be the best type of joint to use on any specific installation.
I just know from experience what has traditionaly been used in the past and some of the present.
SAE appears to have come out with some other very good quality fittings for holding hydraulic pressure, such as the type of fitting that Derek mentioned to secure the trans lines at the transmission. This type of fitting allows more of a quick disconnect but yet holds back the pressure of the fluid from leaking.
It is designed to get tighter as the pressure increases.
Which allows you to disconnect the fitting when the car is off relatively easy.

Test run #2:

35 mile drive in 3rd gear (no TCC lock) at 2800-3200 RPM @ 77ºF ambient. Trans fluid temps reached as high as 187ºF, which was also the engine coolant max temp. After I slowed down, trans fluid temps dropped to 181ºF after idle for 5 minutes. So far I'm liking how this thing works. Driving the car this way makes it feel like something totally different, like it's not the same car as it was in 4th gear!

Interestingly, I checked fluid level, and it isn't low after the bypass opened.

Thanks for the explanation, Aaron.

Now I see what I couldn't see... The threads themselves are pretty much the same, but the main diameter of the male and/or female changes as they move forward.

Thus, for those of us without quick-release, the cooler adapters are straight-threaded, with a cone in the end that matches the original (45*) flare...

Derek may be correct - the male could be the one that's tapered, not the female. But the idea is the same.

AA wrote:

Derek may be correct - the male could be the one that's tapered, not the female. But the idea is the same.

To make an NPT fitting, you would tap the hole with the proper diameter NPT Tap which is tapered from the top of the tap, and becomes progressively smaller toward the tip of the tap, and the male plug in your drawing would be tapered as well. I believe there is a degree or two of difference between the taps and the how the plugs or fittings are made. (Would have to look up the NPT Standards to be sure of how much of an angle difference the standard is.) This provides for a better seal after tightening then down. But in a water or fluid situation you can use a pipe dope (thick liquid) or teflon tape or pipe sealant in a tube with PTFE (Teflon) in it and allow some curing time.
The key to making a proper NPT joint is to start tapping the hole and pull the tap out frequently to not only clean the threads but to test fit the plug. Repeat this procedure until you have the plug set as deep as you want in the threaded hole.
This is what we've done to the 2 coolant ports in the LIM that feed coolant to the TB. Use NPT Tap and plug until you get the plugs flush with the surface of the LIM and that effectively blocks the coolant flow to the TB.
Seal with the liquid teflon.

Up until this point we have only discussed an NPT joint as a plug filling a hole. But you will find on your cars engine that most if not all sending units that need to seal a fluid or gas after installation are usually NPT. i.e., the Oil Pressure Sending Unit, Coolant Temp Sending unit, Knock Sensors, to name a few.
All the gauges that are installed in my air compressor at home are NPT threaded. The gauges in my hydraulic press are NPT and read up to 30 ton.
The NPT fitting has it's place in all industries not just automotive. Very common in plumbing, etc.

The main reason I went with NPT thread is because it's a common option you can get from JEGS, Earl's, Russell, and other hose & connector manufacturers. There must be an automotive application for it, as they stock an entire isle of -AN to NPT adapters. The thread pitch at least is the same (I could fit 3/8 NPT over a 5/16), however the 5/16" NPT seems to be nonexistent. I do agree the NPT may not be compatible with 45º flare, just explaining why I chose the NPT thread. It is very close to our transmission line fitting. If it were the correct size, I think it may have worked.

Test run #3:

35 mile drive in 4th gear with lots of heavy throttle at 2000-3000 RPM @ 78ºF ambient. Trans fluid temps reached as high as 185ºF, settling to 178ºF after idling 5 mins. Seems like once the thermal bypass opens, the Tru-Cool MAX acts like a brick wall for trans fluid temp, making it hard to go above ~185ºF.

Test run #4:

30 mile drive in 4th with some heavy throttle @ 88ºF ambient. Fluid temps maxed briefly at 189ºF, but settled at 187ºF, same as coolant temps max.

Getting ready for a 350 mile round trip with the trailer tomorrow morning - hauling home the family grandfather clock. Wish me luck!

If I could figure out how to do this, I would copy the parts from Advanced Auto that are listed to make connections to the OEM radiator.
But if anyone is interested go to : AdvancedAutoParts.com and do a search for P/N 240390.
That will get you to the fittings necessary to tap into the existing Radiator / Trans Cooler.
They have the proper flared fittings to fit our radiator and barbed fitting for the hose.
In case what ever kit you buy does not come with them.

I'm pretty confident the hose clamps are going to hold just fine. I think the main reason we've heard of clamps leaking is because the hose gets old and weak, and it cracks; or the elasticity of the hose is lost and the clamp slips off because it's too loose; or someone tightens them incorrectly (very easy to do). Torquing the clamps correctly and using the braided jacket high temp/high pressure hose probably eliminates the need to worry about this, or at least it has for me. I may pursue the -AN fittings in the future, but for now I'm pretty sure these clamps are okay.

After my 350 mile trip with the trailer, the trans stayed nice and cool. Yesterday was a 55ºF day, but I still tried to get the trans fluid temps up. With the empty trailer on, my wife and I, and some things in the trunk, I drove over 100 miles at near constant 80 mph in 4th gear, through rolling hills. This kind of activity would probably push the limits of our transmissions, I would never have tried this without the cooler. The result was a peak of 198ºF, which quickly lowered to 192ºF after slowing down to 70 mph. On the way back added a 300 lb grandfather clock (looked like a dead body under the tarp, lol) and about 200 lbs of dishes to the load, drove in 3rd and 4th gears through some serious hills; trans fluid temps peaked at 194ºF. Btw, props to F-Body calipers and Hawk HP+ pads for providing easy downhill braking the entire time. I estimate we were pushing 5300 lb total.

If you can't tell, I'm super impressed with this cooler. Last summer it was very easy to get the trans up to 220ºF just by driving the car hard, and with no extra load. And once I reached that point, it was hard to get the temp go back down. Now I can watch it go up and within a minute it starts to settle back down close to 185ºF, a little higher if towing, but that's to be expected.

Very cool. (No pun intended)
I am going to install one as well.
I want to put a hitch on it and pull a utility trailer occasionally, as you do, with out worrying about hurting the trans.
I recently got an extra good deal on a new Aeroforce gauge (100.00) that will allow me to monitor temps while driving as well.

I currently have a seeping / leaking OEM Trans cooler line that needs replacing.
I'm wondering if i should order that line new and then cut it for a cooler or just run hose from the existing steel tube to the cooler and cut out the bad portion.
I'll use an Earl's compression fitting to make the transition if i do it that way.

I like the Earl's compression fitting idea, or you could flare the end of the cut line, then adapt to a hose fitting.

If you know where there's another Aeroforce for $100, please let me know.

AA wrote:

I like the Earl's compression fitting idea, or you could flare the end of the cut line, then adapt to a hose fitting.

If you know where there's another Aeroforce for $100, please let me know.

This one was from a guy on another board that was getting out of the whole modding thing.
Hooked it up once to the OBD port and never used it again.
Have verified by the model and serial numbers, it is of the latest revision from the company for our GM's, so it turned out to be a very good deal.
Don't know that I'll find another like it. But what goes around, comes around.
If i see one, I'll be sure to let you know.
I think this gauge and the AutoTap i bought from Derek will provide me with all the information I need for now.
I don't intend on installing any more upgrades for quite a while.
It's time to focus on preventative maintenance on my car and some upgrading and maintenance of my Motorcycles.
That will consume the budget for the summer.

Hose clamps will hold a transmission line just fine. I've used them on builds where the tranny has had a modified pump installed and there was no issues, and repaired countless (read probably hundreds by now) of lines using clamps. If you are concerned, simply use the 3/8" fuel injection clamps. They are more than capable of the job.

I think the concern is the 96 PSI operating pressure, which is more than double what you'll find on most automatic transmissions. If there's a weak link, it's going to rupture on our cars before all the others. I think it's fair to assume most kits are not intended to see pressures that high.

But I agree hose clamps will work, I just prefer to use the stronger hoses for insurance.

Fuel injection clamps will have no issue with those pressures.

If you want to make sure, simply put a slight flare on the end of the steel line, it will hold the hose and prevent it from slipping off if clamped.

These are the clamps you want, not worm gear style.

I believe those will work. But the problem isn't always the clamps. It's the rubber hose, imo.

AA wrote:

I believe those will work. The problem isn't always the clamps. It's the rubber hose, imo.

Modern rubber transmission line won't have any issue with 100PSI pressures. It may seem high, but most transmission hose is rated for more than that. The stuff from GM isn't anything special compared to the stuff you buy off the roll these days.

When I go back to work, I will look up what our Goodyear hose is rated for. I believe it is in the 200+psi range. More than anything it will see in our vehicles.

The only issues I have ever seen were people using the old style fuel line as transmission hose. It was only rated for about 50psi and would burst and would swell in a short time and turn into mush.

I have noticed GM doesn't use clamps on rubber hose for the transmission line. They use a metal line with flared fitting.

ZZP and INTENSE both claim there is a risk to using rubber hoses with clamps. Even the instructions that come with these kits say not to double clamp - they know it could cause the hose to crack. And you don't need to search far online to find horror stories of hose connections coming apart with transmission cooler installs.

The hoses might be rated, and the clamps may be rated, but together I don't trust them, based on what I've read (explained earlier in this thread).

Meh, I can see them giving that warning due to liability reasons, but I have yet to see a clamp or hose failure when properly installed. Maybe I've just been lucky, but I have yet to see one when done correctly. Then again, I'm not trying to sell pricey flared and crimped lines either....

I don't mean to argue with you, and I am most certainly not calling you a liar, it's just real world experience versus internet stories tells me otherwise...

And I apologize, as I didn't read through all seven pages.

But, I will keep that in mind when I have a customer come in with that complaint. Thank you.