2001 2500HD auto trans heating up

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).

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)

P.S. I should have mentioned that it is the 3 speed plus OD tranny, not an Allison. When the temp nears 200 the fan engages and there is a loss of power. Truck has 56K with normal maintenance at 30K.

---Ken>

what engine? How heavy is the camper? I ask which engine as the fan will pull some power when it kicks in. Also confused by what you mean by 56K with "normal" maintenance at 30K. Whitelightning

There is no cause for concern with 190 degree tranny temps. THis is normal range (180 to 200) so is not cause for concern but you do not want to get much above 210 on a long hard pull and if you get to 220 and above, it is time to throttle back and gear down and let it cool a bit. It is not that it will toast at 225 but it will take a toll in tranny life.

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.

how many have you run with the mix in it ?

(deafening silence to follow)................

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

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

The "power" the cooling fan uses is the least of your concerns when towing heavy loads, only its cooling performance is important.

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.

Is there any standard as far as which line is the input to the radiator tranny cooler, the upper line or the lower line.

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

If your 2001 2500HD came with a factory transmission fluid temp guage it probably also has a factory external transmission fluid radiator. Look in from of the regulatopr. My 2002 2500HD has one as part of the trailer package. The guage will run 190-200 pulling a

6000 # trailer >>When towing a fifth wheel or carrying a camper my Silverado seems to

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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

Take one 5.0 or 5.3 put a heavy load on it, and have the fan kick in, especially if its a seven blade fan, and you will notice a drop in power. In this case the owner has a 6.0 so it shouldn't be a noticeable factor. Asking questions is how one makes a diagnosis. Try it sometime.

Whitelightning

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

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

Snoman is an idiot! He has no clue. But you know that already.

Ian