Technical Trans cooler in the radiator

What I need to know is it best to have a cooler in the radiator and possibly a auxilary cooler somewhere else instead of just having one in front of the radiator. My 55 Sunliner originally had a air cooled trans so no cooler in the radiator,I stuck one on the radiator and worked fine until a long trip and got it hot. I now I think I got a good trans in it and want to be safe this time,I never got a trans hot when there was a cooler in the radiator and read that it was better for them to warm up some.

 

You could run both. Use the one in the radiator then tie it into an auxiliary cooler in front of the radiator.

 

I do not want to take any chances this time,just the cooler in front of the radiator worked fine for a few years but it got expensive getting the car home from Florida.

 

I had an extra one on my pickup with a camper and towed.
When I had a new radiator built for my 56, which had an air cooled transmission, I had one added since I knew I was going to modernize. It serves 2 purposes a cooler and a heater also to add heat to a cold transmission to get it to operating temp quicker and then to maintain the correct temp. If your not going to tow or race I would only have the one in the radiator like the transmission your putting in was designed to use.
There is a lot written on having an automatic transmission fluid maintained at a certain temp. Our older ones like mine never see over 160-170 because of my thermostat. It should probably be higher..

 

My understanding is it's better to have the cooler in the radiator. The ATF works best if it's within a specific temp range, something a external cooler can't control as well unless you use one with thermostatic flow control (which they do make, and are recommended for severe-duty applications). Too cool ATF is just as bad as too hot. The cooling system is thermostatically-controlled and will do a better job of maintaining that temp. Not to say that may not be inadequate under certain circumstances. If it's determined or wished for that more cooling is wanted, probably the best solution is an auxiliary cooler installed in-line with the flow through the cooler before it enters the radiator. That way if the cooler over-cools the ATF, the radiator can bring it back up into the preferred range. This has the advantage of removing heat load from the cooling system; instead of having to absorb the ATF heat, the radiator can shed heat into the ATF instead. A win-win....

I suspect those air-cooled Fordomatics were a warrantee issue for Ford. I've run into way more than a few of those that had been converted to water cooling and very few of them looked like 'bootleg' conversions.

 

Steve has it right!

 

Ok, here's my 2 cents. I rerouted my cooler lines that were originally piped only to the radiator because I noticed that the warmer the transmission got the higher the speed it took to get my 700 R4 to go into 4th gear. I have no proof but I suspected it had to do with fluid viscosity which I think we all know is related to temperature.

I added a fluid to air heat exchanger in front of the radiator and repiped through a temperature control valve. The fluid goes through the radiator until it reaches 180 degrees and then it switches over to the heat exchanger in front of the radiator. And yes I noticed that difference in the 4th gear engagement speed.

This is the valve that I used.
https://www.summitracing.com/parts/...jvUfl10JuFSDIQwMVW7sWCiPq6EbO8HwaApoQEALw_wcB

 

Now to figure out what radiator to use,I do not like the looks of ones made in aluminum but can not afford a brass version. Auto City Classics have one for around 229.00 and will paint it black.

 

Just an FYI. There was a study from a motorcycle message board which was cross-posted here on the HAMB about 10 years ago where they compared Aluminum, Brass, copper, and painted radiators. They determined that the painted black radiators dispersed (conducted/transpired/radiated/whatever the correct word is) heat better than any of the of the non-painted radiators. Seems counter intuitive, but they used a bunch of different colors of paint also and determined good ole black paint was the best. Don't remember if they determined if gloss or flat black was better though.

 

The cooler in the radiator is to also help the ATF warm up as well as to keep it from getting to hot.

 

I'll suggest to junkyardjeff that he also install a fluid temp gauge. ATF breaks down rapidly after 250deg or so.
On my ot truck the trans fluid is fairly well matched to the coolant temp unless towing some big weights.

 

My OT dodge pickup runs an aftermarket cooler between the condenser & radiator , THE in radiator cooler is bypassed. Been this way for 235000 miles , trans was rebuilt at 175000..YMMV

 

I've had automatic transmissions with remote coolers, not connected to the radiator, for decades with no issues. Last car was 40 yrs. this way when I sold it, and the same transmission and cooler. All 3 of my cars with automatics currently run auxiliary coolers separate from the radiator. I personally don't want my radiator temps affecting my trans cooling.

 

The need for cooling kind of depends on the application. Stock, or nearly stock engine, coverter, etc the in-tank cooler is probably sufficient. A higher stall converter will generate more heat, this can be a problem when driving over longer distances on the highway, as the trans can generate more heat than the stock cooler can remove; the closer the stall speed is to engine rpm at highway speed, the worse this becomes.

 

My old motorhome has an Allison. There is a temp gauge redlined at 220 (I think) and a red light and alarm that sounds at about 220. I had it heat up once climbing out of Oak Creek Canyon is AZ. Slow traffic steep grade and converter below lockup speed.

similar could be a good setup for any auto, Cheap to implement and you can be sure what the temp is.

 

The only reasons a separate cooler in front of the radiator or elsewhere are going to cause a trans to overheat is that you do not have adequate air flow or it is just flat too small for what you are doing with the rig.
The being too small usually relates to rig pulling a heavy trailer.
Inadequate air flow could be any of a dozen reasons.

My 98 BMW 528I came from the factory with a separate trans cooler in front of the radiator with no connection to the radiator at all. It sits between the AC condenser and radiator beside the power steering cooler. 280K on it with no issues except it had a leak caused by the accident the previous owner was in.

 

For a street driven car, the radiator mounted ones are ok. The only issue I have seen is when they mess up and the trans ends up pumping antifreeze.
Worked on lots of new cars with separate coolers.
I run separate coolers on trucks.
I would say the only wrong answer would be not having a cooler for a non-air cooled trans.
I’m planning on adding a trans temp gauge just for curiosity purposes.

 

I’ll add, BBC/TH400, maybe 65k miles no issues with just air cooling, actually below the radiator. Only trans issue was a stuck valance in the valve body, but I don’t think that had anything to do with not running it through the radiator

That said, it we could have found a radiator with a cooler in it at the time, my dad would have probably used it

 

Just a note to add regarding trans cooler built into the radiator (integrated). I once had the radiator/cooler tank assembly fail, which put coolant into the trans fluid. No externally visible signs. Long story short, failed trans.
So, rebuilt transmission and new triple core radiator (with remote cooler). All good you might think. A few weeks later, kicked something up off the road into the fans, which blew apart. Another new radiator and new fan set. That's life.

 

i have read that you should paint a radiator with lacquer paint as the others (rustoleum) tend to insulate the radiator and they will run hotter

 

Based on advice, the consensus is to run transmission coolers in a series, from pressure outlet of transmission through radiator first and then through an auxiliary cooler before going back to transmission. Running it this way allow it to get to operating temperature quicker.

Firstly, the reasons for this is that if the transmission fluid is hot, it will be cooled more quickly and efficiently by the radiator. Secondly, if it is cool it will be warmed up and yes it can run too cool. When they run cool condensation that may be in the system remains there, NOT GOOD. The transmission needs heat for self preservation but not too much.

If the fluid is too hot after it leaves the radiator it will be cooled by the auxiliary cooler before going back to the transmission. Auxiliary coolers needs to be mounted where airflow isn't impeded as it needs to dissipate or radiate the heat, air flowing through and over it does the job in removing the heat. If stuck for space a small slimline auxiliary cooler with a fan could be the go.

In colder areas and on short trips, the transmission may not get hot enough to reach optimum operating temperature. By being routed through radiator firstly it will be heated to a better temperature.

I checked my late model in the garage and this is the way the big manufacturers now do it. They spend $M on R&D so why not take advantage of their expertise, it's free. I wouldn't just run an auxiliary cooler, my opinion, but definitely use your radiator. Why, because the transmission generates the second greatest amount of heat beside the engine.

Run fluid line through the radiator first and then back through auxiliary transmission cooler. I've seen small air deflectors used to push air over and/or coolers in some instances where space is an issue. Don't have it too low so that you run the risk off loosing it due to road clearance issues. Last thing you want to do is grenade your transmission due to heat buildup and heat will kill them eventually. I've never been a fan of just a stand alone transmission cooler in isolation.

Normal transmission range is between 180F- 250F with pan temperature @ 60mph being 180F. Any more that 20mins @300F and you could need some repairs. When towing a load the temp can easily rise to 250F. Pull a steep hill or grade, tow a trailer and it'll easily rise to 200F+, continue to do things it wasn't designed for and you could easily destroy it by boiling.

Good fluid is pink, red means used, Brown or with a red tint means too long.

 

The problem with adding a gauge is, where to put the sender? The only practical space for it is the sump, but what you really need to know is the temp of the oil as it exits the torque converter.

 

What happened is I had the cooler attached to the radiator and debris got caught between the two so I think that is why it got hot,the cooler looked too small so I put another on it but this time its about a inch from the radiator and I might not had it where it got the best air flow. I actually tried to hide it so it could not be seen but made 5 other trips to Florida with not problems,its going to have both the one in the radiator and a external.

 

You can install the sender in the cooler line with a T fitting.
Installed in the line to the cooler (converter out) would give you the highest temps.Installed in the pan would be like an average temp.

 

In my off topic truck, I replaced the radiator with one that didn't have a trans cooler in it, so I added an external cooler attached to the front of the radiator. This truck gets driven year around, and has an OD trans.

In the summer, it works fine, but in the winter, whenever the temp gets below 15 degrees, it takes at least a mile before the trans will shift correctly, its pretty slow on all the up shifts, and the OD won't kick in until the trans temp reaches 70 degrees, according to the service manual. I'm at the point that I usually let the truck warm up a bit before I drive it, that pretty well solved the issue, unless its really cold. Gene

 

Holy CRAP!! I would be callin' in sick...

 

I seen where a guy used 2 sensors. 1 for each line.
He could toggle between the 2
Just tossing that out there.

 

Put a manual 'box in it. Problem solved.

 

How long does it take for the engine thermostat to open? Cold rad until then.

 

According to info from Summit your cyl. wall wear is 3 times higher @ 160 vs 180-190......