2001 2500HD auto trans heating up

When towing a fifth wheel or carrying a camper my Silverado seems to be overheating the tranny, even though these loads are well within the rated
capacity of this truck. The tranny temp gauge shows about 190F when the fan starts to engage I understand there is some kind of "protective mode" for the transmission when it gets too warm. The dealers I have talked to don't seem to have knowledge of how this works. Recently there was a kind of ringing noise (an extra noise) in the area of the tranny when I stopped after a hot day of carrying the camper up and down hills, though the noise was not there the next morning. I am wondering if others have had similar experiences and how concerned I need to be. Thanks.
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I have a 2004 Chevy 2500HD with the Allison tranny and I can tell you that when towing a heavy trailer throught the NC mountains 180-190F tranny temp was normal. My tranny gauge usually runs 120-150F here in FL while driving around town during the day (stop-and-go), but I had no problems at 180-190F in the mountains last week while towing in the heat with a total weight of 4000+ lbs.
If you believe you are having issues, check with Allison's web site for technical info on the 1000 series tranny, plus a filter change couldn't hurt either (easiest thing to do on this tranny with the external spin-on filter).
Cheers - Jonathan

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once more
biggest cooler that will fit behind the grille
bypass the radiator cooler
if you're really serious, use a mix of Dex3 and MobilOne 5w20 synthetic engine oil (50-50)

fan
for
don't
similar
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"TranSurgeon" wrote:

If you are serious about not screwing up your tranny, do not follow this advise. NEVER mix engine oil with tranny fluid. Also, you can overcool your oil but there are those that seem to think they know more than the engineers that designed and built them and will tell you otherwise.
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how many have you run with the mix in it ?
(deafening silence to follow)................
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We run 50-50 mix ATF and Synthetic motor oil in our race car PowerGlide. The last one lasted 10 years and would still be in there if the planetary would not have exploded. The clutches and band looked new, and went back in. Unfortunately the valve body gasket we got had the wrong holes for the brake and it destroyed itself.
Al
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The
would
brake
Al;
Before I put this in customers' vehicles, we ran it in:
86 Ford Ranger 84 Dodge B-350 86 Bonneville 91 Dynasty 92 Voyager
it works, and works well; currently have at least 30 HD vehicles out with this mix
the only one I'd be leery of is the Mopars that use the ATF-4, it might cause TCC chatter
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On Wed, 03 Aug 2005 14:34:40 GMT, "TranSurgeon"

How does using that mix affect shift quality? I'm assuming it makes it firmer?
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I thought there would be a change in shifts, but no, it felt the same

PowerGlide.
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"Big Al" wrote:

in.
the
And I used to run 10 to 15% kerosene in my automatic trannies when it got to 50 below, so what? I used to drag in the 80s with a friend, alchol and the hole bit running over 700hp on a built up THM 400 with a 5500 RPM stall converter. We ran regualr ATF and never lost first tranny but did a few engines and rear axles until the quirks were works out. Sure maybe it works for you but you have no data to support that it would have not done the same with just ATF in it and a 10 or 12 sec blast down a strip is nothing like hauling 10 or 12k up a hill on interstate when it is 90 plus outside.
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TranSurgeon wrote:

TranSurgeon wrote:

Snoman is an idiot! He has no clue. But you know that already.
Ian
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yes, but amusement is where you find it
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My '04 2500HD with the Allison already has a huge external transmission oil cooler. Are you suggesting that he bypass the factory external cooler and put in an aftermarket unit, or did you just not realize that it already had one?
Cheers - Jonathan

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yes, but does HIS 01 2500 have an Allison or a 4L80E ???????

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"Jonathan" wrote:

cooler
It is EXTREMELY foolish to bypass your built in cooler but some think they know more because of a name. The tank cooler helps stabilze your tranny temps and keep the range of temp swing a lot narrower because you tranny will work better and last longer with a more constant temp. If you follow the advice to bypass cooler completely, you will have a sluggish tranny in cold weather and possible reduce cooling in cold weathewr as well because the thick oil will have considerable more drag and resistance to flowing thru a big cooler when cold. Also, when you try to dump all of the tranny heat completely in front of radiator with a BIG cooler you will reduce A/C effectiveness because air reaching it will not be virgin and it will be hotter and it will reflect back to engine cooling to and a added restriction to airflow path too. Even the warm tank water can cool the tranny fluid some and since the tank water circulates rapidly on a hot day it will still cool oil some without effecting engine cooling as much as a full bypass. The correct way to do it is tank first then aux cooler and if your temp are at or under 200 towing there is no cause for concern at all. I have a 26 year old THM400 that has had a very hard life with a small aux cooler after tank cooler and it still works like new and a 16 year 700R4 with 173k and same setup and it still works like new to. I have been if cars with too big a cooler or a full bypass too and they do not fuction well in cool and cold weather.
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wrote:

Is there any standard as far as which line is the input to the radiator tranny cooler, the upper line or the lower line.
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I've just tried all this stuff. '87 Chevy Pick Up, THM400 transmission. 'Mr Transmission' guy says to bypass the rad cooler, -"as it's probably plugged anyway".
I go home, do as he suggests and as I'm about to pull my trailer for the first time in my life, I install a temp. gauge in the trans oil line. Not pulling the trailer the tranny runs at about 100 degrees... max 110 on a hot day. Too cold I figure. When pulling the trailer she is about 175 to 190. The trailer part is OK but we have winter here and if I can't get her up over 110 in the summer she will be worse when minus 30 degrees.
The instructions that come with the kit suggest as you do, that I run first through the built in cooler then the aux cooler. I'm thinking... this isn't going to work. If I'm cooling too much already, by doing it like the instructions or you say I'm going to end up with the same or even less temperature (the rad cooler cools it some then the aux cooler, -now starting with a cooler transmission oil, cools it even more).
What I did.
First I ran it through the aux cooler. This drops the temp to about 100 (from my original testing). Then I run it through the original rad cooler. This then heats the transmission oil to about 140 - 150 degrees when my engine is warmed up and running around 190 degrees. Seems to be quite stable but I've yet to pull the trailer with it set up this way. I'll be testing that shortly.
Dave
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wrote:

you ever actually try plumbing it this way? it works fine on my '88 K2500 w/ a 700-r4. it shifts fine when it's -15F (3 out of 4 mornings in January), my AC works wonderfully even when it's 98F out (aka last week). my truck's temp doesn't creep up anymore while pulling my 14ft box trailer loaded at 6500lbs, like it did plumbed conventionally. I also dropped my trans temp from 225F to 175F while towing my trailer.
your logic boggles the mind as far as heat transfer goes... I don't even know where to start. the heat shed by the external trans cooler is but a fart in the wind compared to a 250F-300F AC condensor.
-Bret
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"Bret Chase" wrote:

You have never seen -50, I have and minus 30 or 40 a lot. Strange thins happen at those temps. ALso because you do not understand the physics of heat exchange it does not make them change to your liking. Your logic is the bizzare one because the 250 to 300 degree temps you claim exist only in the first few passes in condesor. You need to cooling it to close to ambient to get best cooling from A/C and better than half the condensor is used to lower the refrigerant that last 30 or 40 degrees The laws of thermodynamics tell you that as the tempature differentail between the item being cooled on the ambient air decreases the efficency of the heat transfer drops as well and if you use a aux cooler incorrectly it impeds this process by placing more warm air than needs to be in front of condensor and reduces the cooling of the freon. Calling this process a "fart in the wind" just tends to show a lack of understanding of the whole process and the thought that goes into designing one from the factory. Also GM gave up trying to get their A/C to cool properly all the time and Dmax powered trucks because before 2004 and 1/2 model. The intercooler was in front of condensor (simular to a big aux tranny cooler) they has since relocated it behind the AC condensor and resigned themselves to using a bigger intercooler in a warmer airstream.
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wrote:

I'm happy for you, but what does -50F have to do with w/ anything I said?
. ALso because you do not understand the

"first few passes" on a parallel flow condensor? tell me how that works.
The laws of thermodynamics tell you that as the

know what? nobody gives a shit about the AC.. the topic is "Re:2001 2500HD auto trans heating up" in reference to this topic.. removing the trans fluid from 195F water to even 110F air is an improvement to the trans' cooling.
Calling this process a "fart in the wind" just

The transmission's heat output 96% of the time *is* a fart in the wind, it is no comparision to the heat load imparted on the radiator b the condensor.
-Bret
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