Max Trans temperature?

[trapper]

I installed the remote filter and temperature sending unit, now I have this cool gauge, but I don't know what the max trans temp should be. Any suggestions? BTW, it's a 91 ex with 31s & 3.55s, and I installed a larger remote cooler. I searched, but couldn't find an answer....

 

[Maniak]

I've asked many people (including here) and it all comes down to where you read the temp and who you ask..

Some Trans places say "keep it under 150F" which doesn't tell you much.. Keep the temp where at < 150.. Also, different parts of the country will end up with diffrent temps..

For example.. I can go out to the truck that hasn't been driven all day and have a pan temp of 130F when it is 105F outside.. In my case, keeping the pan temp at < 150 isn't possible..

I just look at "what is normal" temp when on the freeway and figure about another 10-20F when in town with the converter not locked up.

Fluid starts to break down at about 250F if I remember correctly, but what I haven't been able to find is how long it has to be at 250 before it has a problem.. If it at 250 in the converter, but then cools back down at the coolers, is it ok?

Just to be safe, I change my fluid (what is in the pan) every 2 oil changes (10k-12k miles) and the filter every 20-25k miles. Even though I've seen my pan temp hit 190 (really hot days, in town) The fluid has never smelled burnt or looked brown (just not as bright as it was going in).

I am running 2 coolers (one plate, one tube/fin) with a pusher fan from a Toyata 4 runner to help in stop/go traffic (only runs when my converter isn't locked). My front Cooler is far enough away from the radiator that the engine fan doesn't really pull the air across it so I added the extra fan (it draws 8 amps when running)

It may be time to try to make a thread specifically for Trans temps and make sure people put the ambient temp and where the sender is.

Oh.. keep in mind, my temps are also high because I'm running a 700r4 and the flash stall with my current converter is almost 2800rpms.. and its Darn hot in Southern Arizona.. But in general, my pan temps are about 70F above anbient temp on the freeway and 80-85F above ambient temps when in town (when its 105f+ out, that gets the fluid hot).

Here is a pic of the gauges I use (I watch temp and pressure since I have a TV cable that "must" work or I will kill the trans) and of the coolers

~Mark

 

[trapper]

What's wrong with my tranny then? I'm getting almost 200 degrees in mild ambient temps in stop & go traffic. During highway travel it'll stay around 160. I haven't even pulled anything with it yet! I have the sending unit set up so that it measures the oil temperature as it comes out of the transmission before it gets to either cooler, and I have my external cooler mounted where yours is, however I haven't put a fan on it (yet).

 

[410Fortune]

200 is about normal for a stock cooler type system, also where is this 200 temp being read?
I like to read the temp from teh trans pan, not from the cooler lines, this tells me what the majority of the fluid temp is at.
Mine sits at about 135-160 during normal driving, has seen 165 when it is hot outside.
Believe it or not towing the boat has little effect on this temp unless I hit a steep climb.
the highest I have seen is 185, which is okay with me, the Mercon III with the addition of the Lube Guard addative should be just fine at 180-185, I would not get worried until I started to see 200+, pull over at 215-220.

A larger cooler will do WONDERS for your temps.
Larger is better, but the cheapo fin style coolers dont always work the best.
The cooler needs to be mounted where it will get good airflow.

I have a B&M cooler on my BII, its the motor home size, in combination with the 2 core aluminum radiator the temps stay nice and low.

 

[spindlecone]

No Coolers, just an oversized (3 QTs) finned alum pan, have never seen my temps over 170 on a 90Deg Day, in town, measured at the pan.
70 Deg days, 140/150 max.

 

[Maniak]

If your reading 200F where your filter is, and your filter is on the transmision outlet side between the cooler and the transmission (i.e. going from the trans, to the filter, to the cooler) you are reading about the hottest fluid in your transmission circuit.

The fluid goes from the torque converter (which is the hottest part) to a line that normally goes to the cooler, from the coolers back to a line (coolest part) that goes back to the transmission.

200F at the hottest part isn't bad.


~Mark

 

[trapper]

I replaced the stock cooler behind the grill with one that came out of a super duty (I think), but it was twice the size of the stock one. The highway driving reading is telling me that I'm not getting enough airflow through the cooler, I need to run a fan on the cooler, because when towing a big load up a steep hill, the load on the transmission would be the greatest and the airflow would at a minimum

 

[410Fortune]

yes but dont forget that same fan will actually block some air flow when its not being used....especially mounted as a pusher....
Do you have a fan shroud? Is the cooler shrouded so the air must go through it (air will just go around the cooler/radiator support without a shroud)
What is your water temp?

 

[trapper]

The water temp has has always seemed to be cold to me, the stock gauge will bearly read into the normal range, and this reading can be verified in the winter time by the lack of warm air from the heater. Even when the tranny cooler setup was stock and the tranny was puking fluid out the vent hole the motor never got close to hot.

 

[Maniak]

How far away from the Radiator/condensor is your tranny cooler..

As you can see in the pic above.. my tube/fin style cooler is right against (1/2" or so) the a/c condensor.. I can feel air blowing through from the radiator fan (it hold paper against it easily)..

My 2nd aux cooler is too far away.. When at idle or even with the rpms up, there is almost no air flow through the plate style cooler (paper doesn't stay on it). That is why I added a fan to it.. I did set it so the fan turns off when the converter is locked up so it won't block much air when I have good airflow going over it from speed.

 

[Glacier991]

This thread actually covers the issues really well. Trans fluid temp will vary depending on where it is measured to start with, as noted. Fluid in a normal trans will probably by between 175 and 200 on a non cooler tranny - so long as you are not measuring it at the hottest point in that design (the hottest fluid comes from the convertor).

Any system that is keeping the oil between 150 and 175 is serving you and the tranny very well. "Keep it below 150" is nonsense. Fluid's normal range is between 150 and about 210. Higher temps degrade fluid faster and hence require more frequent changes. Synthetics resist deleterious effects of heat better.

Lots of good advice in this thread. I may sticky it a while for the duration of the summer.

 

[BrooklynBay]

Transmission life expectancy chart:
Dead Link Removed

 

[trapper]

Where in the chart does it show the temp where the tranny starts barfing fluid out the vent, and onto the exhaust, causing a huge smoke screen that stops traffic? Haha Been there and done that!

 

[410Fortune]

puking fluid is not always because of heat.....and its not a good thing

but typically you toasted the ATF when it gets that hot!

 

[BrooklynBay]

Here's a link with additional information: http://www.tciauto.com/cooling.htm.

 

[BKennedy]

Here is a pic of the gauges I use (I watch temp and pressure since I have a TV cable that "must" work or I will kill the trans) and of the coolers

~Mark

Looking at this picture, it looks like you have the secondary cooler installed behind where the stock cooler would go. Did you remove the original cooler to get this one in there? I am thinking of getting the largest cooler that will fit, and throwing the original one away. It looks like the fan you installed is in the location of the original tranny cooler?
Oh, did you have to pull the radiator to get that in there, or did it fit from the front?

 

[BKennedy]

Just purchased a 15X7.5X3/4" Flex-a-lite cooler from Summit. Should fit under the stock cooler against the radiator near the top, unless my measuring is off.

 

[Albino 94LTD]

What is not mentioned (and what I want to know) is the amount of time at a certain temp.

If the tranny is running for 2 hours at 240f or more, yeah I'm sure that's bad, but how about 240f for 10 minutes several times a month?? I popped up to 240f today going up a 2 mile 10%grade hill, ambient temp 90f, with the fan on.

Glacier, input please.

 

[Maniak]

Looking at this picture, it looks like you have the secondary cooler installed behind where the stock cooler would go. Did you remove the original cooler to get this one in there? I am thinking of getting the largest cooler that will fit, and throwing the original one away. It looks like the fan you installed is in the location of the original tranny cooler?
Oh, did you have to pull the radiator to get that in there, or did it fit from the front?

Our 92 didn't come with a stock cooler..
But, yes, the smaller cooler is mounted about where the factory one normally is and I put the fan in front of that (its a tight fit, but it does fit between the grill and the 2nd cooler).

The front cooler was put in w/out pulling the radiator (fan too).
The bigger tube/fin style cooler was a tighter fit. I had to loosen the radiator and condensor and scoot it back some (against the fan) so I could fit the cooler between the vertical support that is in front of the radiator and the condensor itself. The tube/fin style cooler is held on by those plastic things that you push through the radiator. I am going to change it to a plate style and make a real mounting bracket for it.

When I ran just the smaller cooler (w/out the fan) the temp wasn't much cooler in around town driving since the cooler was too far away from the conensor and the engine fan wasn't pulling the air across it. Adding the 2nd cooler helped some but it still wasn't cool enough for me (and it did raise the idle temp of the truck). Adding the fan makes it so the temp will drop at idle (to about 70F above ambient temp) but the engine temp is still higher than it was before the 2nd cooler.


~Mark

 

[snocross1985]

Albino - If you saw temps of 240, I would consider changing my tranny fluid to be safe. Better safe than sorry when it comes to your tranny.