ATF Temp-How hot is too hot?

[domstriker]

After dealing with the pink milkshake three weeks ago, I got a B&M Supercooler and a scan gauge. I put the cooler on after I put on a new radiator and drove it for about a week while I waited for my B&M.

Under my normal driving conditions, the hottest my ATF got was about 220 in 90 degree heat running the ATF through the radiator's tranny cooler..

After I put the Supercooler on, the hottest I've seen it is around 200 in 90 degree heat. I completely bypassed the radiator and the B&M is the only thing cooling the ATF.

To get to the point of this thread, I did some moderate wheeling today. Lot's of uphill driving on the first portion of the trip. ATF got up to 280 degrees. I got out of my rig to check things out and could smell ATF. It was very noticeable. I checked for leaks but couldn't find any. ATF level is perfect.

So, 1.) what's with the ATF smell and 2.) how hot is too hot?

 

[kball]

So just to get this straight, you got a new radiator and ran it using the built in cooler until your B&M came in. Then you installed that and bypassed the radiator correct? So how did you plug the radiator cooler connections? I made plugs using 3 inch pieces of hose and a bolt in the end. I've noticed that as the radiator heats up it has caused heat expansion in the cooler part and has forcced some tranny fluid past my bolt plugs and has dripped onto the skid plate. Maybe something similar is happening to you and that's what you are smelling. Or you are cooking your fluid. 280 sounds too hot to me. Are you using synthetic? If not it's definitely too hot! And what model B&M are you using?

 

[jdmaccord6]

wow, 280 seems very hot. In this scalding Texas (high 90's so far) stop and go traffic, i've seen right around 199-200 as the hottest temps and that's with an external tranny cooler. Normal temps have been around 150-170 on average. I think because you were wheeling it which caused it to get that hot. If you constantly wheel in those conditions you might think about getting an external fan to mount on the cooler too.

 

[domstriker]

So just to get this straight, you got a new radiator and ran it using the built in cooler until your B&M came in. Then you installed that and bypassed the radiator correct? So how did you plug the radiator cooler connections? I made plugs using 3 inch pieces of hose and a bolt in the end. I've noticed that as the radiator heats up it has caused heat expansion in the cooler part and has forcced some tranny fluid past my bolt plugs and has dripped onto the skid plate. Maybe something similar is happening to you and that's what you are smelling. Or you are cooking your fluid. 280 sounds too hot to me. Are you using synthetic? If not it's definitely too hot! And what model B&M are you using?

Yep, you got it straight.

After I hooked up the B&M, i connected a hose to the plugs at the bottom of the radiator and tried to blow out as much fluid as possible. As far as plugging them, I just used the little blue rubber end caps that came on the B&M. I have noticed that I already lost one. Will some synthetic Amsoil keep it noticeably cooler?

I'm using the 70268 version. The one that most people on here are using. Also, I'm not using synthetic fluid. I'm just using some Valvoline Max Life ATF.

 

[domstriker]

wow, 280 seems very hot. In this scalding Texas (high 90's so far) stop and go traffic, i've seen right around 199-200 as the hottest temps and that's with an external tranny cooler. Normal temps have been around 150-170 on average. I think because you were wheeling it which caused it to get that hot. If you constantly wheel in those conditions you might think about getting an external fan to mount on the cooler too.

Yeah, it's been hot where I live the past couple of weeks. 95+ degrees. Just driving to and from work will only get the tranny up to 170. Most of it is flat highway miles though.

The only time I notice it getting close to 200 is when I'm going up hills and driving around in stop and go traffic around town.

 

[kball]

I'm using that cooler as well but I have no temp gauge on mine. Need to do that...

So as you've experienced those little blue caps don't work too well. Especially with no clamp on them. I would run some hose from connector to connector to seal off the cooler. That might work better than my plug set up that has spit out some leftover trans fluid due to the heat expansion.

I bet you have trans fluid all over your skid plate and who knows where else so that might be where you are getting the smell from.

The synthetic won't keep it cooler. Synthetic can take a lot more heat without breaking down than the regular fluids. I use Dexron VI.

 

[domstriker]

I'm using that cooler as well but I have no temp gauge on mine. Need to do that...

So as you've experienced those little blue caps don't work too well. Especially with no clamp on them. I would run some hose from connector to connector to seal off the cooler. That might work better than my plug set up that has spit out some leftover trans fluid due to the heat expansion.

I bet you have trans fluid all over your skid plate and who knows where else so that might be where you are getting the smell from.

The synthetic won't keep it cooler. Synthetic can take a lot more heat without breaking down than the regular fluids. I use Dexron VI.

Is it OK to use Dexron VI even though the manual says to use Dex III?

Here's another question...At which point does the scangauge measure the ATF temp?

 

[kball]

Is it OK to use Dexron VI even though the manual says to use Dex III?

Here's another question...At which point does the scangauge measure the ATF temp?

Dex VI is completely compatible. Here's a good link comparing performance of both.

DEXRON®-VI - GM Techlink

I believe the scangauge gets it's info from the ECM. There's a sensor in the side of the trans that tells the ECM what the temp is.

Someone who has a scangauge could probably answer that one better.

 

[domstriker]

I forgot to mention this as well.

The passenger side floorboard and center console were extremely hot when the tranny was running hot. I'm wondering if this heat was from the tranny, exhaust, or both. My girlfriend kept asking if her seat warmer was on.

 

[quicksilvr]

Here's a couple charts to look at:

280 is WAY too high. You should probably change your fluid since you know you got it that hot in the first place. The life expectancy of the fluid just went way down from being subjected to that.

 

[domstriker]

Here's a couple charts to look at:

280 is WAY too high. You should probably change your fluid since you know you got it that hot in the first place. The life expectancy of the fluid just went way down from being subjected to that.

Those are some good graphs. Those temperatures reflect oil pan temperatures though.

While I'm not denying that fluid life is shortened by hot temperature, those temps reflect oil pan temp. As kball pointed out, the 4r's ATF temp sensor is located at the send line of the tranny. So the 280 degrees that the sg read did not reflect the actual operating temperature in the pan. I'm wondering what the temp of my ATF was in the pan when the sg read 280.

 

[RunningRick]

i am running duel coolers on mine since its a 115 here in phx in the summers and in my sending line im seeing an average of 170 to 190 depending on the driving im doing i have mime plumbed in a tee that is grounded up at the trans cooler this lets me see the max trans temp before cooled so im quiet happy with that temp coming out of the tranny i definately believe that 280 degrees is way to hot to becoming out of the transmission

 

[domstriker]

i am running duel coolers on mine since its a 115 here in phx in the summers and in my sending line im seeing an average of 170 to 190 depending on the driving im doing i have mime plumbed in a tee that is grounded up at the trans cooler this lets me see the max trans temp before cooled so im quiet happy with that temp coming out of the tranny i definately believe that 280 degrees is way to hot to becoming out of the transmission

I thought about running dual coolers as well. I'm wondering what would be more beneficial, two coolers or one cooler w/ a fan.

 

[domstriker]

I just read that the Valvoline Max Life ATF I'm using actually is a full synthetic.

 

[RunningRick]

i may also add a fan because i took it out wheeling on friday and driving in sand can heat the tranny fluid up in a hurry so i would add this just for this situation. and i also here adding a fan would help with the ac as you have more air flowing over the condensor when not moving

 

[quicksilvr]

Those are some good graphs. Those temperatures reflect oil pan temperatures though.

While I'm not denying that fluid life is shortened by hot temperature, those temps reflect oil pan temp. As kball pointed out, the 4r's ATF temp sensor is located at the send line of the tranny. So the 280 degrees that the sg read did not reflect the actual operating temperature in the pan. I'm wondering what the temp of my ATF was in the pan when the sg read 280.

I know for a fact that a regular analog temp gauge with sensor placement by a remote spin-on filter generally reads about 15 degree's cooler than the SG2. This is just a guess, but I would say pan temp's are generally about 25 degree's cooler than what SG2 reads.

So 280 was maybe about 255 in the pan. Which is still really hot. Even if SG2 reads 40-50 degree's hotter (which I highly doubt) you're still talking about 230-240 at the coolest point. Again, way too hot for long term transmission health.

 

[domstriker]

I know for a fact that a regular analog temp gauge with sensor placement by a remote spin-on filter generally reads about 15 degree's cooler than the SG2. This is just a guess, but I would say pan temp's are generally about 25 degree's cooler than what SG2 reads.

So 280 was maybe about 255 in the pan. Which is still really hot. Even if SG2 reads 40-50 degree's hotter (which I highly doubt) you're still talking about 230-240 at the coolest point. Again, way too hot for long term transmission health.

That's great info. The remote filter is still pre cooler though, right?

I was thinking the same thing about the pan probably being at least 260ish. I'll probably flush sooner than later. I'm also getting a fan for the cooler. I wonder, had I had a fan last weekend, how much cooler my ATF would have been. It's just kinda crazy that driving uphill at about 15-20 mph for about 6 miles would get it that hot.

 

[domstriker]

I emailed Valvoline about their Max Life ATF.

Here is what I wrote:

What is the maximum safe temperature for your Max Life ATF? I understand that the life of ATF is determined by the temperature that it's operated under.

The reason I ask is because while 4wheeling last weekend, the temperature of my ATF got up to 280 degrees F at the send line to the cooler. I don't know what my pan temp was. I'm wondering if I should flush my transmission or if your Max Life ATF can handle operating at that high of a temperature.



Thank you for your questions. If the temperature of the transmission fluid reaches 280*F for a long period of time, the life of the fluid would decrease quickly, within a few thousand miles. If the product in your transmission is a conventional fluid, Valvoline would recommend replacing that fluid with the Valvoline MaxLifr Dex/Merc ATF. The Valvoline MaxLife Dex/Merc ATF is a full synthetic fluid that will with stand temperatures above 280*F, but the life expectancy of the fluid would decrease slower than a conventional fluid.


Thanks for the response. The fluid in my tranny right now is the Max Life Dex/Merc.How much of an improvement does your Max Life ATF offer over conventional ATF at high temperatures?



Conventional transmission fluids are not designed to with stand high temperatures like synthetic fluids such as, Valvoline MaxLife Dex/Merc ATF. The flash point of the Valvoline MaxLife Dex/Merc ATF is 395*F. Conventional fluids can flash between 330*-350*F.


So are you saying that my max life ATF is okay after being exposed to 280 degree heat for one hour?


The Valvoline MaxLife Dex/ Merc ATF can easily withstand extreme temperatures of 280*F for an hour but, if your vehicle is maintaining this temperature you may want to have a transmission repair shop look in to why the transmission is reaching these temperatures. The transmission should run temperatures under 200*F.

 

[quicksilvr]

That's great info. The remote filter is still pre cooler though, right?

I was thinking the same thing about the pan probably being at least 260ish. I'll probably flush sooner than later. I'm also getting a fan for the cooler. I wonder, had I had a fan last weekend, how much cooler my ATF would have been. It's just kinda crazy that driving uphill at about 15-20 mph for about 6 miles would get it that hot.

Yep, pre-cooler.

Yeah, I agree it seems like 280 was hotter than you would expect under those conditions. I have the same cooler (B&M 70268), and the hottest I've gotten mine is 205. I have it mounted sandwiched between the condensor and the radiator, and it's up high. It gets alot of air from my engine fan. Where is yours mounted...and is it stacked right on something, or is it "free-floating"?

Thanks for posting that Valvoline info. I use MaxLife as well. I plan to keep the temps below 200, and drain and fill every 30K. When I did a full service (pan off, new filter, fluid flush) everything looked good. So I hope to keep this transmission running strong till 300k. My son (who is only 1) can hopefully drive this thing on the original engine and tranny in 15 years. :trophy:

 

[domstriker]

My cooler is on the passenger side on the ac condenser. I used the zip tie things so the cooler is tight against it.

I've been reading a lot on this and it seems that when driving below 35 mph, there is not substantial airflow through the cooler. I think this is precisely why it got so hot. Driving uphill at speeds under 25 mph doesn't provide much cooling action through the cooler w/o an auxiliary fan.

Driving at highway speeds in 100 degree heat, the ATF only gets up to about 165. W/o the external cooler, temperatures were as hot if not hotter than the coolant temp at highway speeds which was about 210.

I think it's a fair assessment to say that the b&m keeps the ATF cooler than the radiator's cooler at speeds over 35mph. If you're crawling, climbing, stopping/going in your rig at speeds under 25, the radiator's cooler is going to keep it cooler.

I ordered a fan and plan on installing it asap. I'm going to do the same ride as before and see how hot it gets.