I discovered that the cooler in my rad is plugged. Guess that is why my trans went huh. My question is can I bypass it and just use my external cooler or possibly two of these in line? I don't do any towing right now just pull some hills here in Northern Kentucky.

 

There seem to be different trains of thought with running external coolers and eliminating the OEM rad cooler. I've heard that its actually better to run a really big cooler and bypass the rad cooler completely, others say you need the trans cooler in the rad to get the most cooling.

I am running two fairly large coolers in series completely independant of my rad cooler and have been for a few years now without problems. A cooler gauge is not a bad idea though. I don't have one, but I did take temp readings off the case of the transmission after hard drives with an infra read thermometer and also took readings direct from the solenoid body via laptop interface with the PCM and it seems to run fairly cool even in hot weather.

A gauge is still planned however.

 

It's possible the chicken was your trans and not the cooler. When a trans starts to sluff off clutch linings (or other internal parts), it plugs the cooler which then kills the hard parts. I don't know that's the case with yours, obviously,but it's common enough.

If your main cooler is plugged, you probably have a buildup in the aux too (assuming it was installed while the other was plugging up). Flushing coolers sometimes works but to be safe, I'd put a new one in. I like to have a radiator cooler installed because it des the best job of cooling. In tests on my GM truck, the radiator cooler could pretty consistently knocked 30-40 degrees off, even if it was blistering hot outside. The oil-to-air cooler's efficiency varied with airflow and ambient temps, from 15-80 deg IIRC. If you live in a cold climate, I like the idea of warming the fluid a bit. The trans works better and lasts longer that way (bakes out moisture). The new electronic trnas won't lock the converter until the trans fluid reaches a predetermined temp (88F in my F150). In your locale, you would probably be OK with just a big oil-to-air unit. If you tow, a temp gauge is vital. If you trans is out, now is the time to weld a bung in the side of the pan for a temp sender. You can get the bungs, sender and gauges from AutoMeter (google them too).

Also, especially if you keep the one used cooler, put a Magnefine (google it) inline filter on the return line to the trans. That will catch any junk that comes loose from the cooler and prevents it from harming your trans. this filter has a bypass, so it can't plug up. It's a good longevity/maintenance step anyway. Ford uses them when a reman trans is installed for just the reason I described. When a trans fails, it dumps a bunch of debris into the coolers. Even when flushed (and some lazy flatraters at dealerships have a "let's not and say we did" attitude) you will leave some and it may cause the trans to fail. Ford discovered the Magnefine virtually eliminated this as a problem. Many trans shops do the same thing.

I'm amazed at how cool my C6 runs. It goes thru the radiator then a reasonably big old-style fin-and-tube unit. Even at 18,500 GCVW, it only reached 200 a couple of times over the course of 20 years of towing. Normally, it runs only about 130-140 (pan temp). 140K and going strong on the old C6, and about half of those miles are towing

 

I pulled and flushed the old external cooler and added a second spare i had in series for added peace of mind. I also bypassed the rad cooler.

 

Hi Jim.

I agree about the gauge. The pan is not the ideal location for a trans temp sensor, but its better than nothing. I remember reading the postings of another gent that was running a bauman TCS transmission controller as well as a temp gauge with a pan mounted sensor and observed two different readings for temperature. One reading from the pan was at least 10F cooler than the reading from the TOT sensor on the solenoid body.

I think the best location for a temp sensor is on the outlet cooler line because thats the hottest part of the fluid. I've seen it doen by placing a tee on the line, two inline fittings for the line, and the third one for the sensor probe. You just have to make sure there is plenty of room around the probe to avoid causing a bottle neck in the line. This location also gives you the best possible response time for reading temperature changes.

According to my info, the PCM waits for temperature of 100F before allowing TC lockup. There might be differences from one tranny to the next, but if temp was observed with a pan mounted sensor, it was probably closer to 100F instead of 88F.

 

Hey David85 do you know which port is the outlet on the c6 trans.? I have been trying to think of the best place to install a gauge and your idea is exactly along the lines i was thinking but wasn't sure that it was a good idea My 460 engine is out of vehicle right now so the acess to install a tee is ideal if i knew which line. Any help would be greatly appreciated....

 

Should be the front line. You can turn the torque converter by hand to see if fluid comes out.

 

Hey David: You aren't wrong. I've had sensors in both cooler lines and the pan simultaneously, with a three-position swx to look at whatever I was interested in at the time. After years like that, I just got used to the pan and interpret all other temps from that. FYI, on my C6, 200 in the pan is about 245 in the cooler out line. I hit a deer about six years ago and it wiped out all that plumbing, except the pan, and the body shop didn't reinstall it. Never bother to do it over. Lazy!

It's more how long the oil stays at a high temp than it is the actual temp it reaches. The two places the oil dwells the longest are the pan and the converter, so those are the two most important places to monitor. The converter is the hotter of those two places but the converter is fed from the pan, and you want it fed cool fluid. Basically, I guess, you're generally "more right" by putting the sensor in the cooler line like you said.

FYI, I can read the oil temp in my F-150 through the OBD-II (via a Gryphon Programmer). The factory sensor is in the valve body. I have a bung in the pan for that truck too and will be adding a gauge there too, as well as in the cooler out line. I'm getting all pedantic on that truck too! My name is Jim... and I'm a gauge-o-haulic.

 

Hi Jim, and welcome to gauge-o-haulics anonymous.

I have temp. gauges on my manual transmissions and rearends too. (Now I'm talking about the rearends in my trucks, just to be clear!)

 

Dodge, I'm not touching that one with a ten foot pole, LMAO.

Jim I think your truck has the 4R100 transmisison, right? Very close to my E4OD. Yep, the sensor is on the PC board of the solenoid body. If you drop the pan you will see a plastic cover on the solenoid body, that covers the PC board and the TOT sensor is on top of that PC board.

Makes sense what you say about temps staying high verses getting hot only briefly. You have me wondering about monitoring temperature at the pan as well though. Since I have an overhead gauge console for my EGT and boost gauges, the hole in the dash is fair game for a pod to hold a few more. Maybe I have the makings of a gauge o haulic too.

I need to put my money where my mouth is and at least get a trans temp gauge.....

 

David: The F-150 has a 4R75E. It's easy to set up sensors in all three places with a three way switch (I used a military surplus rotary swx with 1, 2, 3 on it) Then you only need one gauge. That's how I tested the efficiency of the coolers too. I knew the ambient, knew the temp going in and the temp going out.

 

great idea with the 3 way switch and it saves on space and the wallet, thanks for posting the info you and david have been a great source of info. that I have been in limbo over for a couple of weeks. Thanks again Doug.

 

I think you are having a bad influence on me because that sounds like a really cool setup.

Don't know the 4R75E internals so disregard my comments in the previous post.

 

When we all hit rock bottom, we can start the first chapter of Gauge-o-Haulic's Anonymous right here.

 

first the 4r75-e on the f-150 it has a thermal bypass valve block in the cooler lines below the starter
it is a bad idea in my opinion because the thermostat fails
i disable it on any commercial unit i work on or any of my friends vehicles
when it goes south the trans temp just keeps rising and most times the trans is running way too hot but operating below the TFT sensors preprogramed threshold for a MIL light
Coolers , you need the radiator cooler ,reason is heat transfer
it is very difficult to remove heat from oil so a radiator cooler has a much more efficient means of thermal transfer using the coolant
many get by with air only coolers until that one time that they haul a load
the torque converter makes the heat in a trans and thats why the converter is charged by the valve body
It goes from the converter to the cooler and then to the lube circuit
checking fluid temp at the pan is a waste it is the coolest part of the trans
In 89 the air only was eliminated because engineers were afraid that driving in extremely cold climates would cause the trans to run too cold and no converter lockup would occur
didnt do that well in the southern states in summer and was added back into production
1999 radiator cooler was eliminated engineers thought the air only was sufficient and it was a very robust cooler but there were heat related failures a lot of them
so a tsb was released to install a radiator with cooler for vehicles towing heavy loads
i,ve been repairing auto trans for 35 years it needs the radiator cooler