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.

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.

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.

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.

Sounds like you got it right. I think if I ever did any serious slow-speed off roading I'd need a dedicated fan on my cooler as well.

Looking forward to seeing the results after you install the fan.

What transmission temperatures are you guys running when wheeling?

I bought a 2000 SR5 in December and it had an external tranny cooler installed already.

Tonight I got the scangauge II ATF up to 230 twice when wheeling in the snow (I was going uphill both times with lots of wheel spin).

Each time, I stopped and let it cool down below 200 before starting again. I'm guessing 230 is too high or could I have pushed it more before worrying?

I was planning on changing the tranny fluid with synthetic within the next couple weeks anyway, but now I'm thinking I should get a fan for the tranny cooler, or maybe just replace it altogether?
Does anyone have any updates on their fans?

My mechanic said not to worry until the tranny temp gets above 300, seems high but I won't worry for now especially since I'm getting the tranny fluid replaced with synthetic tomorrow.

During hard low speed wheeling my temps are 125 - 145 degrees. (with ambient temps around 50 degrees)

Wheeling in the snow the last couple weeks I've seen up to about 145 degrees as well.

Personally I don't like to see trans temps above 200 degrees. And with the cooler I'm using the max temps I usually see are around 180 degrees (long uphills on the highway).

thanks for the response, I hadn't seen anything above 180 until last night and it was pretty darn cold out too!

I'm going to think about replacing the cooler with something beefier before the summer hits, for now I'm going to keep on eye on it.

Note that turbodudey is getting his trans temp from an analog gauge, being fed from the temp probe by his remote filter. Those temps are considerably cooler than what a SGII reads.....so his 145 is more like a 165 read from a SGII.

It's been posted here on a different thread that wheeling tranny temps too high can be caused by improper mounting of the cooler. It should be mounted flush with the AC condenser directly in front of the fan. If not then you are relying on air movement at speed which you won't get much of while wheeling.

Thanks a lot guys, I'll check out the location of the cooler tomorrow.

After changing to synthetic tranny fluid, my temperatures seem to have dropped significantly.

I went up the same hills tonight and the temp never passed 180.

Sorry for resurrecting this old thread (but hey, at least I'm using the search!)..

Can anyone comment on the statement above? I just mounted mine with about 1" gap from the AC condenser; I went for a drive and then felt the tranny cooler and it felt hot, "almost" too hot to touch. I figured that should be expected, if the operating temp got to 180F?