Transmission Cooler Reccomendations

[mjonesjr]

All the old ones have it too.

no they don't.....my '97 had no such aux cooler....it just had the one in the radiator.....and mine has the tow package....

everything else you posted Will i agree with 110%......you can't over cool a tranny.....espically an automatic....

i am in the process of installing a second aux tranny cooler on mine....
as of this coming Saturday mine will look like this:
Tranny-->Radiator-->Aux Cooler #1-->Aux Cooler #2-->Tranny.....

IF by chance the radiator has a t-stat in it so it wont flow tranny fluid until it gets to a certain temp, then it will hold the fluid in the radiator until it reaches that temp.......THEN it will take that 190* fluid and pass it throught the 2 aux coolers before hitting the tranny, thus cooling it back down to less than 190*........

also, IF you have a tranny temp gauge, you really need to put the sensor in the tranny port on the side.....there is a little 1/8" NPT plug just behind the shifter linkage (i know for sure on 5R55E's, but not on other transmissions) that is used for testing the main pump pressure. You install the 1/8" NPT sensor in place of this plug, then run your sensing wire from the gauge to the sensor.....and bada boom you are reading ACTUAL tranny temperature, not fluid temperature..........

 

[Will]

It's very thin lubricant. The minimum safe temperature appears to be below freezing. And it's not inappropriate for the operating temperatures. Amsoil is of course bending it for their own benefit, but they indicate the red area is borderline, not outside of its operating range.

But I wasn't too worried about that part of it. Clearly, ambient temperature in within it's operating range. And since the vehicle is unlikely to actually cool the fluid below ambient, I think it's very safe to say that overcooling is impossible. Maybe the real danger of putting too much garbage in the lines is restricting the flow too much. I would replace the factory aux. cooler and put in one of those fancy fan ones with a thermostat switch for the fan.

 

[MAKG]

There isn't a single transmission temperature. You always measure the fluid temperature. The important variable is that the sensor be immersed in flowing fluid.

The hottest spot is probably inside a clutch pack, the torque converter, or the oil pump, depending on what the transmission is doing at the time. None of those are good places for a temperature probe. As a replacement, I'd suggest putting the probe at the transmission outlet port (on the way to the radiator/cooler) if you want to monitor internal transmission temperature, or on the OTHER line if you want to monitor the cooling circuit. Note that these will yield very different results.

Note that those temperature diagrams don't say where the temperature is to be measured....but they suggest it's the cooler output. That's the coldest spot.

Will, there is a difference between continuous operation at ambient, and a warm-up cycle. Certainly, you won't blow up the transmission from a few minutes operation at ambient in a normal climate. But it's far from clear that continuously operating the transmission there is a good thing. A transmission has to be vented somehow, so there is a small amount of water vapor that gets in through the vent. Continuous operation below the boiling point (everywhere in the transmission) may allow some accumulation. It can't be anywhere near as bad as for crankcase oil, since there is no combustion.

 

[oldmantruck]

you should be able to find a cooler on ebay in the 30- 50 buck range( including shipping) there are also 10 inch fans on there for about the same if you get the relay and thermistatat, so you should be able to piece together the electric fan type cooler for about 75 bucks rather than spend $185. might just take a little more tinkering.

 

[97ranger4x4]

Sounds good guys. BTW my temp gauge is on the bottom of my transmission pan and submerged in the fluid. I will check ebay and some other places for tranny coolers with fans.

 

[mjonesjr]

There isn't a single transmission temperature. You always measure the fluid temperature. The important variable is that the sensor be immersed in flowing fluid.

no.....really? The transmission temperature sensor being placed in the 1/8" NPT plug hole will have fluid running over it.....try and take that plug out with out spilling fluid......the sensor is the EXACT same sensor that is sent with the water temperature gauges.....putting the sensor IN the tranny itself gives you an acurate reading on what temperature the tranny is running at, not what the fluid temp is inside the line....just like the engine temp is recorded INSIDE the engine, not the radiator hoses...

I'd suggest putting the probe at the transmission outlet port (on the way to the radiator/cooler) if you want to monitor internal transmission temperature, or on the OTHER line if you want to monitor the cooling circuit. Note that these will yield very different results.

and the outlet port location will show roughly a 20* LOWER temperature than the spot that i suggested putting the sensor......so if the sensor is at the outlet on the tranny line, then you are NOT getting an acurate reading.....when i had my sensor in the tranny line by the radiator, i was reading a 20* LOWER temperature than were i have it now......tranny temperature should be read just like an engine temperature is read, from INSIDE the tranny, not were it is cooled....

Note that those temperature diagrams don't say where the temperature is to be measured....but they suggest it's the cooler output. That's the coldest spot.

yes that is the coolest spot, but why would you want to measure the coolest spot? your engine temperature isn't measured at the radiator, it is measured were it picks up its heat, the engine.......why would you want to read the tranny temp after the cooler? that isn't the most accurate spot since the fluid will heat back up after it enters the tranny......you should read the temperatures from INSIDE the tranny itself.....

 

[MAKG]

mjones, you're confusing pressure with flow. Try the following thought experiment:

Put a foot long extension on your oil pressure sender, and put a temperature probe in it. If you remove the probe and run the engine, you'll get oil everywhere. But there is no flow with the probe installed.

That you will spill fluid out means there is pressure. Not surprising at all on a pressure port... and whether the probe is in flowing fluid depends on the geometry of the port. It's not hard to imagine it being longer than the probe.

There are a few reasons you might want to put a probe at the cooler outlet. Most importantly, if you are going to rely on a graph to draw conclusions you MUST match its assumptions or you'll simply be wrong. Another reason is to measure the effectiveness of temperature regulation -- and in particular if the cooler is big enough (which was after all the question at hand). But it's not an appropriate place for measuring transmission temperature.

Accuracy depends on what you are doing with your gauge. You're fooling yourself if you think pump temperatures are the only variables. What you would really like to know is the temperature at the seals and clutches. So, why do you think the pump is a better analog than the transmission fluid output (NOT the cooler input -- there are several feet of substantially cooled line in between)?

 

[mjonesjr]

the sensor does have flowing fluid over it. The pump port shows a higher temp than what it shows in the line. I have had my sensor in BOTH locations, and speaking from experience, the pump port is a more accurate tranny temp reading than that of in the line by the radiator......

 

[MAKG]

Please answer the question. Why do you think that the pump pressure port temperature is more accurate than the transmission fluid output? "From experience" is vague and unverifiable, and please don't confuse the two ends of the cooler line.

 

[mjonesjr]

i did answer, can you read?

here let me waste my time and answer it again for you:
because it is inside the tranny itself. Speaking from experience, the sensor inside the tranny itself shows a higher reading that in the line; roughly 20* higher. By the time the tranny fluid has reached the cooler, it has already cooled down from what the actual interior temperature of the tranny is.



OMG i forgot you are the technical advisor, you know all....

 

[MAKG]

That's a higher reading. Not a better reading.

You're assuming they are the same.

As I said earlier, what you would like to know is the temperature at the seals and the various clutch packs, but that's not easy.

It is not at all obvious that the pump temperature is more closely related to those than the output temperature.

 

[Will]

Excuse this long paste, but it's worth reading...it's from HERE

ADDITIONAL OBSERVATIONS AND RECOMMENDATIONS


If you are going to use a high stall converter, tow, haul heavy loads, have a lifted vehicle with big tires, etc, we strongly recommend installing a temperature gauge to monitor the fluid temperature inside the transmissions pan. The fluid in the pan is primarily fluid that has just returned to the transmission after passing through the heat exchanger located inside the vehicles radiator. Locating the temperature gauge sender in the transmissions pan will tell you whether your vehicles temperature control system can handle the temperature management properly. We have installed and monitored all vehicles that have been through our shop over the last eight years and consistantly see 140 to 160 degree F in the pan when the factory cooling system is working correctly. As an observation; the temperature between what you see on the engines temperature gauge and the fluid temperature inside the transmissions pan should always maintain a 30 to 50 degree F spread! Always!

Remember, the temperature you observe on the gauge is telling you the fluid temperature after it's been cycled through the radiator heat exchanger! This reading has nothing to do with how hot the fluid got inside the torque converter. If it reached 300 degrees F inside the torque converter and you only see 150 degrees F at the sensor in the pan, it doesn't mean the fluid wasn't overheated and degraded! We do not know of a reasonable way to monitor the fluid temperature inside the converter, so we always assume it is very high during hard work situations. Locking the converter during high heat production situations is the only way to prevent the overheating from occuring in the first place!

The manufacturers of Dextron III transmission fluid have told us that a continuous steady 150 to 160 degrees will yield maximum longevity for the fluid. This is not possible because of the various driving situations you subject the fluid to so proper management of the torque converer clutch is the only reasonable way we have found to eliminate fluid degradation from overheating. I'm sure most of you have seen the charts that show the rapid destruction of transmission fluid properties as operating temperature increases. Most charts show a 50% loss of fluid life for every 15 degrees of operating temperature increase above their designed ideal operating temperature, normally 165 degrees F. This is the reason we recommend each fluid cycle start at 150 degree F. or less.

We also recommend a complete annual flush of the transmission fluid. We have a very simple method we teach our customers so they can change the whole systems volume not just the 4 1/2 to 5 quarts you can change by draining the pan.

 

[MAKG]

That explains a few things. Especially why 200 deg is listed as "bad" for ATF. It's not actually measuring anything meant to resemble peak temperature, but is instead looking at cooling capacity.

SOME heat is lost through the pan as well (by conduction).

 

[97ranger4x4]

How do you flush your entire transmission. I have always just dropped the pan and changed the filter.

 

[Wicked_Sludge]

the easiest way is with a fluid exchanger (in other words, have a shop do it). theres also a procedure that involves removing the cooler line, but i wouldnt reccomend it for novices as its easy to ruin a tranny if not performed properly.