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Old 06-22-2012, 08:14 PM   #1
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Trans Temp Max?

2007 Suburban w/5.3L and tow pack.

I hit some steep grades yesterday in 90F heat. For the first time since I have owned it (6 mos) the trans temp hit 214F. Is this high enough to be a concern?
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Old 06-22-2012, 08:52 PM   #2
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GM says the tranny fluid and parts starts to fail at 270... so if you flirt with that often you'll be doing damage...
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Old 06-22-2012, 09:11 PM   #3
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270 F is just too high. That's a DO NOT EXCEED kind of number.... I would fit a larger transmission cooler. These are not expensive, and can save serious $$$ for transmission work.

I added a B&M 70274 cooler to our F250 (less than $100) and we've not yet exceed 200F even pulling long steep grades at low speeds. This uses a simple orifice bypass; here in CA we don't need to worry about overcooling, but temps reach 130F on the freeway even in the winter time.

Of course, on slow dirt roads, I generally use 4L to allow the transmission to lockup at speeds that keep the Airstream happy.

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Old 06-22-2012, 09:16 PM   #4
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here's a handy chart. Note that it says avg temp, so momentarily reaching a high value isn't the end of the world, but seeing that often is breaking down your fluid much faster.

Mine has briefly hit 180 or so while towing up a long hill in 100+ weather but that's the worst I've seen so far, with the factory trans cooler that came with the tow package.
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Old 06-22-2012, 09:38 PM   #5
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Those B&M coolers Bart mentioned are great. I installed one (smaller model 70264) on my 2010 Jeep Wrangler. No I don't tow with the JK, but it's factory trans cooling ability is pretty weak just pulling it's own weight on a hot day in Death Valley.
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Old 06-22-2012, 11:19 PM   #6
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Thanks for all the info. I need to look into a bigger cooler!
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Old 06-23-2012, 06:17 AM   #7
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The PCM will go into "limp" mode if the tranny temp stays above 280*.
Read the owners manual for details.
Look for a KNP option code for the HD cooler, sticker should be on inside glove box door.

Bob
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Old 06-23-2012, 08:29 PM   #8
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The PCM will go into "limp" mode if the tranny temp stays above 280*.
Read the owners manual for details.
Look for a KNP option code for the HD cooler, sticker should be on inside glove box door.
==============
I have the KNP code. So, does this cooler equal the aftermarket B&M as mentioned above? Would I benefit from a different or larger one?
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Old 06-23-2012, 10:44 PM   #9
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Check out this thread.

http://www.airforums.com/forums/f463...des-51433.html

I have synthetic trans fluid, and even though it will take more of a beating than non-synthetic, I don't want to see my tranny hit or exceed 200F. It never has so far, and hopefully never will.

BTW, I have well over 20k miles (mostly towing) on this setup and have had zero issues in severe Chicago cold (keeping it too cool as some said would happen).
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Old 06-24-2012, 06:33 AM   #10
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Quote:
Originally Posted by redwoodguy View Post
The PCM will go into "limp" mode if the tranny temp stays above 280*.
Read the owners manual for details.
Look for a KNP option code for the HD cooler, sticker should be on inside glove box door.
==============
I have the KNP code. So, does this cooler equal the aftermarket B&M as mentioned above? Would I benefit from a different or larger one?
Red,

Any tranny will benefit if the towing temps are running high, I used a B&M on our 95 Burb, along with a remote filter and temp gauge,(did not come with one).
On our 06 8.1, with a gauge our temps have never gotten above 200*, IMHO it's doing it's job well, I have not added the extra cooler.
If your temps are running 200 I would definitely do the install. The added capacity will also help.
A complete tranny flush,(replaces fluid in converter) along with a new filter is a good place to start.

Bob
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Old 06-24-2012, 07:17 AM   #11
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You might want to see where the temperature sending unit is located. In the pan, on the line to the trans cooler? Diffferent locations will give different readings and its just good to know the source.
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Old 06-24-2012, 07:46 AM   #12
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Generally quoted trans temps (ie. 150 - 225*, etc.) are sump temps. If we were talking torque converter and line -to -cooler temps, they would be MUCH higher. And that's fine. The allowable MAX temps for the fluid are taken into account by measuring the sump temps, given that there is a constant flow rate and volume throughout the trans and converter at a given engine RPM. (Modern electronic trans can and do regulate more independently via computer than older ones)

Relative to sump temps, I think some of us are overly concerned. An occasional spike to 225* is OK.....running about 200* is OK. I have found that on GM trucks, running solo temps, with a factory HD cooler, are about 70* - 90* over ambient and towing is about 100* - 110* over ambient. So, here in IL, it is normal to see 180* - 200* in the summer, while in AZ on the same day, you may see 190* - 220*. Both normal IMO.

In both cases the sump temp does not harm the fluid....BUT...the torque converter temp might be 400* or more. This is where the oxidation takes place. In both cases, I would stay on a 30 - 50,000 mile fluid change interval.

The chart above is a good one and probably reflects some of the newer, more advanced fluids. Back "in the day" when I was in school, the chart was time based and was more strict....ie. at 350* (sump) the trans would last 15 MINUTES!!!!!

Bottom line, If you live in areas where the trans sump temps are REGULARLY 220 - 225*, get an addtitional external cooler. I like the smaller, thermostatically controlled, fan cooled ones, so I don't overcool up here in the winter.

BTW, Allison is a different animal. My current 2500HD Duramax rarely sees 175* while towing in 80 - 90* ambient, in FLAT Illinois. Seems to run about 25* cooler than any other trans I have used.
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Old 06-26-2012, 07:05 PM   #13
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Thanks dzn. I have been watchingit like a hawk now. It runs 165* in the flats at 70* ambient, and climbs to 212* during a long grade to say 5000'. That is like a five mile climb. So, not too bad, but I wish I could stay under 200*
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Old 06-26-2012, 07:35 PM   #14
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I've got a similiar set-up. 2111 Tahoe with the HD towing package. Get your VIN and you should be able to look up your build sheet. Look for the KSL package that includes tranny cooler, eng oil cooler and a different rear end ratio. It takes the GCWR to 14,000 lbs. I've never towed in that kind of heat but my tranny temp usually will never go over 160.

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