put all the coolers you want on it, and run an in-line thermostat Best to run thru the rad cooler for helping warm it up, then to the thermostat.
For oil temp, you want to warm it up enough for the heat to "burn" off water and contaminates in the oil. I like about 160.
Also consider adding a remote spin on tranny filter while plumbing it up. Easy to change and will collect any trash before the oil returns back to the tank.

 

I bypassed the radiator cooler because every time the tranny got hot, it would overheat the motor. My truck just worked better that way. I never had anything overheat after that.

 

But don't add enough that it restricts the flow. Then the rear half of the trans doesn't get any lube and it will die.

The radiator cooler NEVER warms the trans fluid. I've run tests with thermocouples in the bottom of the radiator and trans fluid in and out of the cooler. The cooler always cools the trans fluid, it NEVER warms the ATF.

 

in line thermo "sounds" like a good idea.
any suggestions?
as to whose.?

 

All the trucks I have seen have a transmission cooler imbedded in the radiator. If you put the extra cooler before the radiator in the oil cooling loop, the radiator will determine the minimum oil temperature going back to the transmission. When towing, bigger coolers are normally always better when setup in this manor.

 

Summit has an inline just for this purpose. DER-13011 $63. 180 deg.
Years ago use a Lockhart oil thermostat for bikes which works well. I am sure there are others.

I would not run in the rad for southern states as Sycostang suggests. keep them seperate. Up North, contrary to Mark's comments, the radiator can help warm the tranny to better operating temps intitially. otherwise it takes quite a while or may never reach even 90 degs. (with a thermostat) There is a circumstance that could if cooling are was excessive, but I won't go into that.

Restriction with too many/large coolers is a small concern and should be managed. both with fluid and air flow. The return from the cooler dumps back into the pan. So it will limit the whole tranny supply, not just the rear half.

If the cooler capacity gets large you may have to put a service loop in so the fluid does not all drain to the pan after shutting off. This will lead to dripping fluid from somewhere due to all the excess fluid in the pan.

Since there are many acceptable ways to provide tranny cooling, all that is up to you. non are wrong if the tranny temp is handled. Do some searching here and you will find discussions in the past on it. Having the gauge so you know is most of the battle.

 

My comments are based on actual tests that I performed over the last 19 years while I was an automatic transmission engineer at Ford. I instrumented the vehicles so that I could always know the temperatures throughout the system. How much testing have you performed? Just assuming that the radiator heats the fluid is just plain wrong.

In cold temperatures the radiator is EXTREMELY efficient at cooling. The water in the lower tank, where the trans cooler is located, is almost always the same as outside temperature. In cold temps the engine thermostat only opens for a few seconds at a time. After those few seconds the water is stagnant in the radiator. This gives it plenty of time to get down to outside temperature.

My data showed that at -40F the only time the lower tank warmed above -40F was when the trans warmed up. Then the lower tank warmed almost to 0F. The ATF going into the radiator was about +40F. How does 0F water warm +4-F ATF?

The radiator cooler is more important in southern states than the northern ones. It is a VERY efficient transmission cooler, and in the hotter states you need all the cooling you can get. It is especially important in low speed, high load situations, such as backing a trailer.

 

Mark
Assuming will just make a$$ out of both you and me. My experiences do differ probably because the vehicles were different. I can see and would agree with the results noted (I learned something), however not all coolers are located in the "lower tank". Downflow rads. eFans also change things for winter perf. And, in all these cases the factory cooling is failing to do the job the way it is being used or modified. To your point though, I was thinking of my 98 which is in the discharge path from the engine. (so you missed at least one thing in your 19 years) His may be a downflow rad just as you described.

For the south (Desert), As Sycostang commented, it is not uncommon for the tranny to overheat the motor. (rad cannot keep up) So many times it is best to add a separate cooler for the tranny. This allows the motor to stay cooler and REALLY helps the AC to do it's job. So since we have recognized the factory shorted cooling for costs, speed or a multitude of reasons. Factory cooling is inadequate for his situation.

Since we are here to assist a man with his cooling interests, I will not speak of this further, and will stay on target with the posters needs. I hope you will do the same.

 

Not to be hijacking this thread or anything, but it seems very active at the moment so I don't think one little question is asking too much is it???

I've just had my C6 rebuilt and I am replacing the in-radiator cooler with one of the B&M fan cooled units from Summit. I have to remake all the hard lines due to corrosion and I was wondering if anyone knows what size the fittings are on the transmission? When all else fails I will measure them myself, but the truck isn't nearby at the moment.

And personally, my opinion on cooling is to keep the cooling systems separate for each component. Dumping heat from the transmission into the engine cooling system right before it re-enters the engine is just plain stupid. Well, in hot climates it is anyway....

 

the radiator i have is cross flow.
direct replacement from checker. even though i really did not need it. i felt the age of the truck called for service here.

the test will be in two days pulling the 9800 load (and my wifes stuff, probably another ton there)

for the time being i am by-passing the rad.
going on two major mountain pulls. and 90 miles of desert. then to 7200 ft..
will let you know sunday or monday how it went.

air temps should range from 40's to hi 80's.....so here we go.

 

ok
bypassed radiator. no thermo.
ran a/c across desert and pulled same 2000 ft desert mountain twice mid day or mid pm. 87 air degrees.
almost got to 160 while waited at border patrol station for 15 minutes. but even going 3850 rpm up hill in heat temp stayed 100 or less.
this by pass method seems to cool to muich....huh..

 

Glad to hear it did not overheat.
Better too cold than to hot for now. Sounds like a thermostat is next. Then if you want to take it in steps. Look to running thru the rad if not warmed in the winter. The real downside to low temps is not evaporating moisture out of the oil. Less of a concern than with the motor where there are combustion gases to burn out of the oil.

The rise in temp sitting could be a concern. Indicate a lack of airflow at idle. The engine fan may have been cycling or the cooler does not get much air from the fan.
Another time you will see a sharp rise in temps is if loading against the torque converter. Basically not running fast enough in a gear to lock the converter or inching along with a heavy load. Braking torquing is another.

As noted. The rad cooler will only help it is in the tank with the discharge from the engine. So you should check that out. But just having the thermostat will be a big improvement to warmup.

ozstang
did you get your answer? The tranny itself is pipe thread. I want to say 1/8, but 1/4 at the biggest. The fitting adapter to the flare can vary and I have seen both 5/16 and 3/8. So can't say for sure.

 

sure did shift better when it got closer to 160 with that big load...

 

I like a digital trans temp gauge (I got the one from jc whitney) It has afaster response time which is important as soon as you see it climb you can make changes to the driving style. You should see the temp climb in the drive thru or at a stop light!! Not to mention when towing, You can tell when you are going up hill for sure.
$50.00 for a temp gauge sure beats a trans rebuild.
You need to make sure the fluid gets to a good temp to burn off water like has been said with a temp gauge you could decide if you can bypass the in rad cooler or not by temporarily bypassing it and seeing the change. Tower hobbies has Duratrax infra red thermometers for $24.00 they are pretty accurate and read up to 450 degrees. The bad thing is you will have to get out and check, But it does have other uses, like checking your trailer bearings, rear end, tires etc. If you have one tire on a multi axle trailer getting hot it could be that the axle is out of alignment or the tire is low!!

 

have one of the digital readers.
checks out perfect to b and m gage.
so i trust the temp feedback.
just guessing i may want to run it thru the rad. to warm it up some now.
hard to think of it in the desert s.w
have 175 thermostat for summer switch to 195 in the winter on rad...