I don't know what the best is; I think most people get Hayden's and have no issues.

Other than that, I'll mention things I learned studying this before I did it, and then what I've learned after.
As to design, plate/fin is more efficient than tube/fin designs, but then it becomes a matter of size - a larger, less efficient one will do the same job as a smaller one if space isn't an issue, and on my Trooper it was not and imagine the same is true for you.

Take a look at this promo piece and you can see the different designs:

https://www.haydenauto.com/upload/Hayde ... oolers.pdf

I went with a tube/fin design, sized for the "Class C Motorhome/towing up to 5k lbs." It is probably a size over what most people would use, but I did that upon some expert advice and do not regret it. I have an auxilliary tranmission temp gauge and what I have observed is that my transmission when cruising (45 to 65 mph) runs at 70 to 75F over ambient temp., with a "floor" of ~110F in the very coldest temperature (e.g., it stays at 110F at any temp below 40F I've experienced (down to 10F)). It runs 90F to 110F over ambient when climbing steep hills or idling in traffic over hot pavement. In my climate, that means I run 115F to 160F in the winter in all conditions, and 140F to 165F most of the time in summer, with peaks to 200F if I climb hills in extreme weather or idle in traffic in the same. I have not towed with it since I installed the gauge and cooler. I love the temp gauge and cooler combination.

Other thoughts from my experience, YMMV:

- I would suggest also that as long as you have the lines open, install a Magnefine or similar in-line filter in the lines as added insurance.
- Dex III works best for me vs. Maxlife or DexVI LV fluids. Others have noted the same.
- Put some lubegard red in the transmission.
- Use constant tension clamps or double-up (reverse direction on each) on the clamps if you use regular hose clamps; mine would weep slightly on the connection to the hard lines with only one clamp.
- There is much argument in some circles about putting the aux cooler before or after the radiator one. Put it after so you get max cooling. It won't get "too cool."

As to which hose/inlet is which, you can trace that from the transmission easily. The one that is connected to the hard line that connects to the transmission about 1/2 way along the body just above the pan on the passenger side is the return line (it is dumping cooled fluid back into the pan). Alternatively, once you pull the lines, have someone hit the starter for a second or three while you watch, the output (to the cooler) one will spew fluid.

Here is the gauge I installed; love it. It was not hard, looks decent, and was maybe $70 total (I had some of the materials - paint, etc.)

 

I don't know what the best is; I think most people get Hayden's and have no issues.

Other than that, I'll mention things I learned studying this before I did it, and then what I've learned after.
As to design, plate/fin is more efficient than tube/fin designs, but then it becomes a matter of size - a larger, less efficient one will do the same job as a smaller one if space isn't an issue, and on my Trooper it was not and imagine the same is true for you.

Take a look at this promo piece and you can see the different designs:

https://www.haydenauto.com/upload/Hayde ... oolers.pdf

I went with a tube/fin design, sized for the "Class C Motorhome/towing up to 5k lbs." It is probably a size over what most people would use, but I did that upon some expert advice and do not regret it. I have an auxilliary tranmission temp gauge and what I have observed is that my transmission when cruising (45 to 65 mph) runs at 70 to 75F over ambient temp., with a "floor" of ~110F in the very coldest temperature (e.g., it stays at 110F at any temp below 40F I've experienced (down to 10F)). It runs 90F to 110F over ambient when climbing steep hills or idling in traffic over hot pavement. In my climate, that means I run 115F to 160F in the winter in all conditions, and 140F to 165F most of the time in summer, with peaks to 200F if I climb hills in extreme weather or idle in traffic in the same. I have not towed with it since I installed the gauge and cooler. I love the temp gauge and cooler combination.

Other thoughts from my experience, YMMV:

• I would suggest also that as long as you have the lines open, install a Magnefine or similar in-line filter in the lines as added insurance.
• Dex III works best for me vs. Maxlife or DexVI LV fluids. Others have noted the same.
• Put some lubegard red in the transmission.
• Use constant tension clamps or double-up (reverse direction on each) on the clamps if you use regular hose clamps; mine would weep slightly on the connection to the hard lines with only one clamp.
• There is much argument in some circles about putting the aux cooler before or after the radiator one. Put it after so you get max cooling. It won't get "too cool."

As to which hose/inlet is which, you can trace that from the transmission easily. The one that is connected to the hard line that connects to the transmission about 1/2 way along the body just above the pan on the passenger side is the return line (it is dumping cooled fluid back into the pan). Alternatively, once you pull the lines, have someone hit the starter for a second or three while you watch, the output (to the cooler) one will spew fluid.

Here is the gauge I installed; love it. It was not hard, looks decent, and was maybe $70 total (I had some of the materials - paint, etc.)

Which gauge and mount did you use for this? Looks great want to do something similar.

 

Thanks ORO, I have that exact gauge already installed. I will find the best fit based on that pdf and see what will work for me. Looks like Hayden is the way to go.

 

Question for ORO, where do you have the temp gauge sending unit installed?

I have a similar set up to you, with the Hayden cooler installed and the temp gauge. With mine, the sending unit is installed in the output line from the transmission to the cooler.

At the recommendation of SurferJoe on this site, I installed the aux cooler before the radiator.

I'm interested to compare notes with you regarding temperatures to determine what effect this has on the temperature of the fluid.

 

Question for ORO, where do you have the temp gauge sending unit installed?

I'm interested to compare notes with you regarding temperatures to determine what effect this has on the temperature of the fluid.

Good point. Different locations will give different temps. Mine's at the test port. The Glowshift gauge I have there came with a 1/4 NPT ( I think ) thread sending unit; that's the same thread as the transmission take-off test port on the "waist" of the bell housing on the driver's side. I just removed the test plug, screwed in the sending unit, then ran the wires up the tunnel. I drilled a small hole in the plated manual clutch cover plate (gold looking plate under the brake booster) to then run the wires into the cabin/under dash area. Jerry had suggested that somewhere in the forum. I had to run another power wire straight from the battery through that hole also to power the gauge unit color memory; nothing at all in the fuse box I could find was truly "always on" - it would interrupt briefly with the ignition and then I'd loose the color memory in the gauge. I used piggy-back ATC blade fuses to switch the high/low lighting with the headlight relay (oh, yeah, so I had another wire from the engine fuse box for that).

RE: temps - Yeah, I'm curious, too, to compare. I wanted to put the gauge in before the cooler, but for some parts availability or other reason it was easier to do it in that order: cooler, gauge later. So unfortunately I did not have base-line, non-cooler temps for my vehicle. That's why I went into detail above about what I see; hoping others might say what they have w/their set up.

I understand SurferJoe has that opinion; and in some climates I think that can make a lot of sense. I believe he is somewhere that has extreme cold in winters; I am not. I consulted some other experts and got the opinion it was safe. Subsequently, I've run my "oversize" cooler as I said down to 12F and it has a "floor" of ~115F; the correlation between internal temperature of the fluid and the outside air temp/speed stops around maybe 35F or so and then cooler temps don't affect it IME. I can surmise this is because the engine is passing on waste heat via the physical coupling of the components (and I have a little data which implies that is a source of transmission heat, too)* independent of the transmission itself, as well as the internal friction of the transmission that heats the fluid in it independent of cooling in the circuit elsewhere.

The location of the sending unit at the bellhousing/in the fluid circuits gives a good indication of what the temp is of the fluid as it heads into the TC and to clutch packs, and not the lower temp that would probably be seen at the return line, I would think.

* And I did not expect this. After I had the gauge/cooler in for about a year, I started adding Lubegard Blue ("biotech") to my engine oil. Immediately my transmission temps dropped ~5F across the board - e.g., cruising, on hills, a little less when in traffic. There is of course no direct connectivity between the two fluid circuits. There's the mechanical coupling via the flex-pate/TC, and then the physical coupling of the bellhousing to the engine. So whatever reduction in temps the additive created in my engine (which it is indeed supposed to do), passed on a measurable drop to my transmission. I was surprised at this.

I don't have any Lubegard Red in my transmission. It's still running on the first full fill after I rebuilt it, just ~10/11 qts of fresh Chevron MD3. This summer later I'll drain and fill the pan, and I'll add it then and observe temps. I intentionally didn't use it with the first fill so I could measure the differences (if any) before/after the use of the additive in the transmission case.

 

Driving around town in stop and go traffic, my temp gauge usually reads between 160-180. On the interstate, it reads about 125. However, I live in East Tennessee where we have ridges and mountains, and I have noticed higher temperatures than you have reported when driving up long, steep grades. For example, the temp gauge has shown 212(f) (100(c)) under these conditions.

There are a couple of factors which may account for this. First, my temp gauge sending unit is in the output line from the transmission to the cooler. Presumably, this measures the temperature of the fluid at its very hottest. Second, my aux. cooler is plumbed in before the radiator, so it is also possible that the fluid returning to the transmission is not as cold in your setup, where the aux. cooler is plumbed in after the radiator.

Another user here, Wesf (I don't know whether he still checks in here; his trooper was totaled in a traffic accident), reported that he checked transmission temps with an odbii reader. According to his posts, those readings showed his trans fluid reached high temp of 180 while towing a travel trailer up a hill. I am curious where the obdii gets its readings for the trans temp. Do you have any idea?

 

Just came across this post and just thought I share how mine is set up. I have the Hayden cooler as well and like it and am using a sunpro trans temp guage, got them both off of Ebay cheaper than Amazon. Upon the suggestions of my mechanic I did not use those crappy zip-tie things for mounting it to the radiator, instead mounted with custom brackets and rivnuts in the radiator support slightly away from the radiator to give it a bit of air space between the two. I also upgraded the rubber lines the cooler came with to some better goodyear brand hoses and I mounted the guage temp sending unit into my trans oil pan versus a line in or out so I could get a actual overall temp reading instead of a reading from the line in or out. Yes I had to drop the pan and weld in a fitting for the sending unit but I feel it was worth it. Also I ditched my factory engine clutch fan for a Hayden oversized electric fan set to pull air in with radiator temp prob/sending unit. Also did not use those zip-ties to mount the fan to the radiator, fabricated a aluminum bracket that bolts to the radiator tabs and has a fan shroud so the fan sucks air across the entire radiator not just a 10-12" circle. So far everything has worked great even driving in the heat of Las Vegas and Eastern Sierras of California. Also recently came across a hood scoop off a Ford Mustang in the wrecking yard so I pulled it off and mounted it to the hood, you could say for extra cooling or the Madmax look of it.

 

What temp readings are you showing with the sending unit in the pan?

 

So I thought I would post my temp readings for my area here in Southern Utah. My temperature sensor is in the test port. I have reached as high as 230°F at elevations of 10,000 Feet during the drive up the mountain on the hottest day of the year. That is the highest temperature I have seen, and it was pushing my Rodeo pretty hard to hit that. If I treated Sancho (my rodeo) easier it would be lower I am sure. I added the Hayden 678 cooler and put it before the heat exchanger since I can see temperatures of -10°F during the winter. I am guessing if I can find the lube guard red it will help a but but not a lot. I am also due for a fluid and filter change. Just gonna see if the local transmission shop will do it since its a pita on the 4L30E while its in the vehicle. I will update on temperatures after that if I find that it lowers the temps any but guessing it wont have any effect.

 

From reading these posts, it looks like placement of the temp sending unit in the test port and the output line results similar temperature readings. I am curious about the effect of placing the temp sending unit in the pan and/or input line.

 

I am curious where the obdii gets its readings for the trans temp. Do you have any idea?

I *think* it is a sensor in/around the overdrive pan. I recall trying to trace the wire from the harness when I rebuilt mine and it ran somewhere in that vicinity. I think I asked Buster one time (years ago) and that was what he said, also. Not positive as it was a while ago and I am fuzzy about it now.

I am also due for a fluid and filter change. Just gonna see if the local transmission shop will do it since its a pita on the 4L30E while its in the vehicle.

If you disconnect one of the radiator cooling lines, you can pump it out w/the internal pump easily. (or just drain the pan if you just want to do a drain/fill vs. full fluid swap). Then you can re-fill it with a cheap and effective pump like this:

https://www.harborfreight.com/Multi-Use ... 63144.html

I know it's "easier" to pay someone to do it, but honestly I don't know that many professional mechanics I really trust to do something as mission-critical as this. If I do it, I know it was done correctly vs. worrying or finding out later it was f'ed up as I have had happen in the past.

From reading these posts, it looks like placement of the temp sending unit in the test port and the output line results similar temperature readings. I am curious about the effect of placing the temp sending unit in the pan and/or input line.

I would think test port/cooler output/pan positions would all yield close to the same temp. The test port is fluid just being pulled from the pan, passed through the valve body but not hitting the gears or TC yet. Cooler input/transmission out line would yield the highest temps I think and not be as good an average read. That's an educated guess, not absolute recommendation.

To me, the test port is just the cleanest install. It requires no modification, gives a good reading, and can be totally reversed back to stock should that be desired.