Write-Up: Transmission Cooler Install

I love the way the front end looks with out a license plate in the way and then add that cooler to it, it's badass.
That's what it would look like with an IC as well.

I want to do some light towing with mine without hurting anything so it looks like I might have play copy cat and get that set-up, especially with the temp by-pass unit or thermostat.

Can you get any closer shots of your hose connections.??

I'm installing in stages. The cooler is only mounted at this point, no hose connections right now. I want to test the location a few days (watch for shifting, etc.) before pluming the lines.

(It looks like his hoses aren't connected yet)

But it looks sweet. I ordered the same cooler.

Can anyone confirm if the stock transmission lines use a 1/4" NPT to connect to the radiator?

AA wrote:

Can anyone confirm if the stock transmission lines use a 1/4" NPT to connect to the radiator?

definitely not. There is an O-ring in a clip-in fitting, kind of how the fuel lines connect to the fuel rail on top of the supercharger. You need a little clip tool and lots of silicon spray to get them out.

deekster_caddy wrote:

AA wrote:

Can anyone confirm if the stock transmission lines use a 1/4" NPT to connect to the radiator?

definitely not. There is an O-ring in a clip-in fitting, kind of how the fuel lines connect to the fuel rail on top of the supercharger. You need a little clip tool and lots of silicon spray to get them out.

Really? the 95 has a threaded fitting..I think its a bit bigger than 1/4 npt , but don't quote me on it...I could have sworn that the 98 had a threaded fitting too...

deekster_caddy wrote:

AA wrote:

Can anyone confirm if the stock transmission lines use a 1/4" NPT to connect to the radiator?

definitely not. There is an O-ring in a clip-in fitting, kind of how the fuel lines connect to the fuel rail on top of the supercharger. You need a little clip tool and lots of silicon spray to get them out.

Really? Jason's original writeup (page 1) indicated that the 'normal' brass fittings that came with the cooler kit worked fine...

BTY, I do like the airflow that Aaron is gonna' get, but I also understand about the potential rock-damage. My friend in the tranny business told me to just get the kit that Jason did and mount it the same way, because the stacked-plate coolers are so efficient that anything will be better than stock...

I agree that Jason's cooler approach is good enough for keeping temps reasonable for towing and some spirited driving in summer. The cooler I used is intended for a different purpose: max cooing under sustained throttle (no TC lock-up) that one might encounter while racing or in long distance towing situations. The Tru-Cool MAX is an extreme overkilll cooler, and I just wanted to see how cool I can keep the trans during the hot summer months. I'm sure it would work pretty well raised up behind the bumper as well.

However, as I said earlier, the location I'm using has always had potential for rock damage to the AC condenser, which has occupied that spot. I just don't see that much damage to it. It's a little dirty with bugs, but not dented much at all - probably because I don't drive much in areas where rocks are prevalent. In the event damage did occur, the mounting location I chose makes it easy to swap out in the event of extreme damage.

PS - deek, I'm talking about the fitting that goes into the radiator. It appears to be threaded, 1/4 or 5/16", not sure.

EDIT: it would seem to be 1/4" NPSF from this info: http://www.tripleedgeperformance.com/4T65E_Tech_Info.html

A source I found says 1/4" NPT has 18 threads/in and has an actual OD of .546". Anyone know if NPSF and NPT threads are compatible?

EDIT: 1/4" NPT does not fit. Hoping 5/16" NPT works.

Moving forward...

Created a map based on Jason's write-up, and the instructions that came with the new cooler. I did this so I could plan where to put the thermal bypass, and to layout the hose runs.



At first I thought putting the bypass up front near the cooler would be best, but the narrow spacing between the tubes on the bypass and the wide spacing of those on the cooler required they be apart to prevent hoses from kinking.

I used a piece of similar 3/8" hose as a gauge to plot the runs and get accurate lengths. notice the sheetmetal making contact:



Bent it out of the way with a pair of pliers:



Here's a shot from the bottom, both hoses approximately the right length:



This shows where I propose to locate the bypass, just above the radiator hose. With 4 hoses supporting it, there's really no need to mount it to anything. I marked the hose length with masking tape:



Two pieces of braided hose cut to length and clamped. It turned out my 3 ft piece of braided hose was cut near exactly in half to fit. Looks like I'm going to need another piece of $20 hose (if you choose to follow my install, buy 6 ft of hose):



Detail of hoses/clamps below. The bypass barbs are not long enough to double clamp. Tightened each clamp to 20 lb-in torque, a max spec I found at an online hose clamp supplier site. Note the open end of the thermal bypass - I thought about which way to orient this, decided down would have the most exposure to elements, so up it is:



For a little insurance, I wrapped it with 3M electrical tape, secured with zip tie. Anyone know if the tape will hold up to ~200ºF?



The next step will be to use Earl's Swivel-Seal connectors to attach directly to the braided hose ends coming off the bypass on the transmission side:



This means no more hose clamps, as the connectors should thread right into the trans line and radiator. I removed the lower plastic cover from the car, found that damn hard to get spot where the lower transmission line connects to the radiator. Soaked it in PB Blaster. It's off to JEGS...

EDIT: tap into the top transmission line at the radiator. This is the return line.

I guess I'm not sure which fitting you are removing.

So Aaron, what size are the threaded sides of the Earl's fittings, for the radiator & trans-line connections... 3/8" NPT?

Trans line connectors are 5/16" NPT, I am 90%. I used JEGS version of Earl's fittings (they are black, and less expensive). These are the ones I used:

90º, helps tap into the OEM return line:



Straight, good for tapping into the radiator:



Both of these lock onto the braided hose (clever idea, easier than a hose clamp), and use -6AN adapters to mate with NPT. I got the 1/4" adapters and they didn't fit. Here is what the adapter looks like:



Problem is, they don't carry 5/16" NPT adaptors, and it seems no one else does, either. Next size is a 3/8" NPT, which doesn't work, sort of. To make things confusing the threads are so close that a 3/8" female will accept a 5/16" male, but a 3/8" male will not thread into a 5/16" female. Went to the local hardware store and picked up some female 3/8" adapters and they fit a 5/16" hose barb adapter from the kit, so I used it to tap into the line going back to the trans mission. But I could not get a 3/8" male to fit into the radiator. Hope that makes sense.

So, I ended up using the supplied hose barb adapter to tap into the radiator, and clamped the hose to it. I plan to find the correct 5/16" NPT adapter eventually and replace it with a black JEGS fitting like above.

I finished the install for now; made a very important discovery that should change the way we do these going forward. After I was finished with all the hoses & fittings (took me 6 hours) I decided to run the car for a few seconds to fill up the cooler and lines with fluid before connecting to the return line. What happened next surprised me - no fluid came out the line from the cooler. Instead, fluid was coming out the return line, the opposite way I expected! What this means is the fluid does not enter the radiator at the top, it enters at the bottom, returns from the top.

The good news: this will make future installs much easier! No need to remove the plastic air deflector on the bottom of the car, and no need to access that hard to each area below the coolant hose. All you do is remove the top trans line from the radiator and tap in there. This is much easier to see and work with compared to the bottom. The trans line to the top is also easier to bend and work with for connecting the hose to the trans cooler. I will change my map diagram in the previous post.

I have some pics and will post them if anyone needs to see, but I wanted to add that last -6AN connector to the radiator before showing the finished product.

Tip: a tube of liquid Teflon thread sealant works much better than the tape for joining threaded adapters and lines.

Btw, this is what happens when you tighten a clamp beyond 20 lb-in torque:

Boy, this just keeps getting better...


- Jason said that his (and my as yet uninstalled) B&M kit came with 5/16" and 3/8" adapter fittings, and he used the 3/8" ones on his '98.

- Aaron says that on his '98 the 3/8" are close but not quite...

- Opening my box just now, the instructions naturally don't tell you what size the fittings are, nor are they marked. However, unmentioned in the instructions but included in the kit is an H-shaped measuring device for sliding over the factory tubing, marked 3/8" on one side and 5/16" on the other... Trying it out on the upper line of my '97, it fits the 5/16" slot!

- Is it possible the damned things have gone metric on us?? I've just mothballed the Wildcat at my brother's house until I've found a new place of my own, and I REALLY don't need to get halfway through this job and find myself stranded because the parts don't fit...


One thing that the instructions do agree with AA on, is that once everybody went to FWD, all bets were off as to which radiator fitting was inlet & which was return... They suggest either doing as Aaron did, and breaking the system open to see which way the fluid flows, or more simply going by heat:

- Set the E-brake good & tight/use a helper on the brakes/chock the wheels, etc.
- Start 'er up and put the tranny in Drive.
- Perhaps turn the A/C on so you have air flow thru the radiator (my own idea...)
- Every few minutes, shut things down and feel the tranny lines to see which is hotter.

Before I move to Oregon, I want to pull the fans, replace what I believe is still the OE lower radiator hose (still has the assembly-line stub hose & nipple,) and put the tranny cooler in in one operation. Thus, the lower tranny connection would be as easy as possible to access.

I have to admit, though, even if Aaron hadn't discovered the reversed flow, I think it would still have been "okay" to use the easier-access upper fitting when you consider how small the factory cooler is, how hot its surroundings are, how little time the fluid spends in there, and the fact that we're adding so much extra capacity to the system...

I had a leak from where I mated the 3/8" NPT adapter with the OEM trans line, so I pulled the 90º bend out and just used the supplied host barb adapter #2 (female 5/16"), hose clamped it. Now things are under control.

Note: even after loosing fluid from the radiator & lines (I used paper towels instead of catch can), and driving 5 miles with a leak, I only needed to add 3/4 quart of trans fluid. I'm sure the first time the trans hits 180º I'll need to add another 1/2 quart or so when the bypass opens.

Here is the area where my lines are going from the radiator to the bypass. The bypass is hidden behind the lines. The OEM return line was easily bent with a pipe bender. No, the return line doesn't come close to touching the idler pulley or the coolant hose:



Here are some shots of the cooler connections:

AA wrote:

I had a leak from where I mated the 3/8" NPT adapter with the OEM trans line, so I pulled the 90º bend out and just used the supplied host barb adapter #2 (female 5/16"), hose clamped it. Now things are under control.

Here is the area where my lines are going from the radiator to the bypass. The bypass is hidden behind the lines. The OEM return line was easily bent with a pipe bender. No, the return line doesn't come close to touching the idler pulley or the coolant hose:

Congratulations on finishing, Aaron!


I have a couple of questions, of course:

- So to be clear, the radiator-to-transmission-line connection is 5/16"? (At least the top one, which would mesh with what the gauge that came with my kit said.)

- You were able to find room for the hoses to pass through about halfway down the side of the radiator, in front of the Maxi-Fuse box?


(Oh, and since you mentioned quantities, a reminder to everyone that the hash-marks or dots on transmission dipsticks are marked for pints, not quarts...)

Both top and bottom radiator-to-trans lines are the same, I'm saying 5/16" unofficially. I tested both with the hose bard adapter that came with my kit.

The 3/8" (-6AN) hoses easily pass through around the side of the radiator, running diagonally. That's the easy part of the install. Leave the ends taped if using braided hose.

Anyone know what happens to air inside a transmission? I assume it just vents out the dipstick tube? Reason I ask, there's a pocket of air in my cooler that will end up in the transmission once the bypass opens. There were no special instructions addressing this issue.

No worry, tranny's have a vent somewhere up high... easy to see on RWD, not so on side-saddle.

Transmission connectors at the transmission do not use NPT threads. They use a flare nut fitting which has a non-tapered thread. Newer ones don't have threads at all, but an O-ring and a nifty clip. I didn't have to unscrew any fitting to get my transmission lines out of the radiator, only release the clip.

My lines attach to the radiator like this:

This thread has me wondering if I put down the wrong size in the write-up... stupid imperial system.

I'll confirm when I do the white riv.

I've been a bit curious following this thread all along.
I have never seen NPT Fluid Tubing connections, they used to always be a standard straight thread with a single or double flared tube at the Radiator (depending on the system operating pressures.) All NPT threads are a tapered thread and not used in this manner. The type of threaded fitting used in the transmission cooling inlet and outlet are more like an AN Type fitting with double flared tubing. Difference being that Automotive uses 45* flare and AN is 37* flare. They are not interchangeable with out the use of adapters or just cutting the steel line and flaring to AN 37* with the proper threaded fitting installed first.
Aviation flaring tool kits can be found on the internet if you feel your going to be using a lot of AN fittings and don't want to use adapter fittings. The more fittings and threaded joints the more you are prone to leaks, obviously. Even after having worked as an Aircraft Mechanic, I don't have an AN Flaring Tool Kit, they were always shop supplied. But they would do tool box inspections periodically and if they found an Automotive kit in your box you had to remove it from the Hangar immediately.
I have also seen, during my short stint at the GM Dealership, the type of fittings that Derek (deekster) is mentioning. But they were never on the Radiator connections but always on the Trans Connections.
The Trans connections is where you have to hook up your flushing machine and all the special tools and adapters were always with the flushing machine. Never did we have to remove a threaded fitting from the Radiator.
Now I left there in 2002 and certainly hadn't seen everything as i spent some of my time in every different dept of the operation and not just on the shop floor, although that was where i gravitated to, due to curiosity and need to know.
So I am very curious to know what is installed in our Radiator's as far as the type of fitting for the OEM Trans cooling lines.
I will either buy a new OEM line from monsterparts just to look and measure or maybe one of you that have removed and cut off the Radiator end of your tubing could send me one and I can then possibly fabricate what it is we all need for an easy cooler install.
Please let me know if anyone is willing to send me a threaded end connector and the short piece of tubing you had to cut off.
Thanks,
Rick

p.s. I would also recommend finding 11/32" Transmission Fluid hose for this install where needed.
It is right between 5/16" and 3/8" and have used it on all Harley's I've either owned or worked on for customers as it has a much higher Temp Rating than other hose we used to use and the 11/32" fit's tighter on the 3/8" fitting to help insure a leak free connection.
The HD's are not running anywhere near the pressures that our Trans our running, but they do run hotter due to the nature of there placement. Close to exhaust and engine.
There is no way around it. I am considering buying the thermostat / by-pass valve sold on the site mentioned for $30.00 to go along with an existing cooler I have for the motorbike. 180* would be perfect. (Thanks Aaron for the link)
If you were to use standard 3/8" fuel line you would be changing it every year.
What I used to be able to buy from Dayco was the same or similar looking braided jacketed hose that AA got from Jeg's. I could get a 25 foot box of 11/32" Heavy Duty Trans hose from them for around $1.25 per foot.
No more. They still sell trans line in that size but it does not have that exterior braided fabric look to it.
It is still rated for the same High Pressure's and Temp's though. I noticed on the sight that Aaron posted for the Cooler that this company also offer's 11/32" Trans Hose in bulk. Will need to email them for more info regarding the hose though.

And another thing.........
I would like a reasonable explanation why the inlet of the hot Trans Fluid is entering the bottom of the Radiator, where all the cool coolant is, and exiting the Radiator at the top, where all the hot coolant is.
Or am I backwards when it comes to the presumed direction of flow of the Anti-freeze or coolant.

deekster_caddy wrote:

Transmission connectors at the transmission do not use NPT threads. They use a flare nut fitting which has a non-tapered thread. Newer ones don't have threads at all, but an O-ring and a nifty clip. I didn't have to unscrew any fitting to get my transmission lines out of the radiator, only release the clip.

Sooooo.... we're talking 5/16" flare?

Also, I assume that you don't have an external cooler because of your trick fittings?

Eldo wrote:

deekster_caddy wrote:

Transmission connectors at the transmission do not use NPT threads. They use a flare nut fitting which has a non-tapered thread. Newer ones don't have threads at all, but an O-ring and a nifty clip. I didn't have to unscrew any fitting to get my transmission lines out of the radiator, only release the clip.

Sooooo.... we're talking 5/16" flare?

Also, I assume that you don't have an external cooler because of your trick fittings?

No, he does have one or did the last time I saw the car.
Unfortunately I didn't pay any attention to the lines or hoses and didn't ask him about it either.

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

Could use another adapter to go 1/8" to -6AN.

First road test today. Drove 30 miles in 3rd gear, last 3 miles in 2nd gear at some good speed. Ambient temp 65ºF. Trans fluid temp topped out at 183ºF, then dropped to 181ºF. It wouldn't go any higher no matter how hard I pushed it. I am liking this cooler - can't wait to test it at 90ºF+.

Note: engine coolant temps were ~185ºF during the test.

Hmmm, I wonder what the angle is on a typical automotive flare, 45*?

Wiki says that the Army-Navy fittings (-AN) are 37*, and I would certainly expect the government to use something unique, expensive and confusing to civilians...

I know for sure the OEM did not use -AN fittings on the radiator. If they did, it would make things SO much easier - all the high performance hose connectors are -AN.