Auxiliary trans cooler

Surprises me that your truck doesn't have one on it? I have a 2009 2500HD with tow package, 6.0 gasser. Mine has a factory cooler on it. I was pulling a 29' Wildwood. My tranny would run around 175 to 190 with minimal hills. Sometimes it would hit 200 on occasion. I would definitely recommend getting one if your truck doesn't have one. One of hardest things on the tranny is extended periods of high heat.


Quick question, what kind of mileage do you get. I usually get 7 to 9, occasionally 10 if I'm lucky (tail wind). My truck has 3:73 rear gears running the 6 speed auto. Wish I ordered the 4:11 now.

As long as your factory cooler is clean and you are within the limits of your truck you should be good to go. There is such a thing as too much cooling in regards to transmissions. You want your transmission to get adequately warm when not towing. This prevents moisture from building up. Also, high capacity tranny pans are a double edged sword too. Along with the fluid taking longer to heat up, it takes longer for it to cool down as well.

It does have a factory one, should have said that in the OP, just thinking of swapping for a larger one. I just thought a bigger one might help in the mountains. Some roads are slow speed, steep inclines for miles. My old 454 saw 1st gear a lot up there, with a lighter trailer.

So the general opinion is leave it alone since it already has one?

Mileage around 8-9 but I haven't pulled it a lot yet, kinda too early to tell. But if that's what it stays I'll be happy with that pulling around 9K lbs.

If it has one. Leave it alone. Believe it or not. You can over cool a transmission. Meaning, that it may keep it a little cooler in the mountains, but could keep it below operating temp on the flats, Especially in cooler weather.

Noticed your signature listed your truck as a 6.0. My calculations don't line up a 6.0 as a 454 c.i. 6.0 is more like 366.142 cubic inch!! 454 is a 7.4397 liter.

However I wish I had one in mine!!! More guts.

CampingN.C. wrote:
So I'm thinking of adding one to the truck just as an extra precaution. What little bit I've towed our new camper, temps have been fine (200).
However, we've got some mountain trips planned this summer with some pretty bad pulls.
From those that have added one, what can I expect to drop temp wise? Also, I'll be pulling the pan soon, what about a high cap pan? I've read mixed reviews on those, especially for the money.

I know the 4L80E is a tough one, just want to keep it that way!

What year 454? I had an 89 TBI 454, the 6.0 is a much better tower. Not sure about the Vortec 454, but the TBI, while reliable, had less power than the 6.0.

I have basically the same truck and tow a 3220BHWE(7430 loaded on the scales). I upgraded my cooler the stock one is small. Just driving around it sees about 125 which is fine for the 4L80E. If you are worried about it being cold get a 165 degree thermostatic bypass. In the summer here in Washington and the west coast pulling the larger grades I have not seen it go over 190, 4000 rpm towing some long grades. It cools off much quicker too and hold 165 to 170 on average.
No need for the pan.

brittsnbirds wrote:
Noticed your signature listed your truck as a 6.0. My calculations don't line up a 6.0 as a 454 c.i. 6.0 is more like 366.142 cubic inch!! 454 is a 7.4397 liter.

However I wish I had one in mine!!! More guts.

Didn't say he HAS a 454, said he HAD a 454. Now has a 6.0

ls1mike wrote:

CampingN.C. wrote:
So I'm thinking of adding one to the truck just as an extra precaution. What little bit I've towed our new camper, temps have been fine (200).
However, we've got some mountain trips planned this summer with some pretty bad pulls.
From those that have added one, what can I expect to drop temp wise? Also, I'll be pulling the pan soon, what about a high cap pan? I've read mixed reviews on those, especially for the money.

I know the 4L80E is a tough one, just want to keep it that way!

What year 454? I had an 89 TBI 454, the 6.0 is a much better tower. Not sure about the Vortec 454, but the TBI, while reliable, had less power than the 6.0.

I have basically the same truck and tow a 3220BHWE(7430 loaded on the scales). I upgraded my cooler the stock one is small. Just driving around it sees about 125 which is fine for the 4L80E. If you are worried about it being cold get a 165 degree thermostatic bypass. In the summer here in Washington and the west coast pulling the larger grades I have not seen it go over 190, 4000 rpm towing some long grades. It cools off much quicker too and hold 165 to 170 on average.
No need for the pan.

This is exactly what I'm wanting to do. The stock cooler just seems small to to me. Did you tow anything before the swap? Sounds like I can expect a 10-15 degree drop while towing? Thanks for the pics!

Yes, I used to have a big block in a Suburban, much more torque off the line but I think the 6.0 is better overall.

Yes towed before the swap. It does make a difference.
The thermostatic bypass is nice if it is your daily driver. I only use my truck to tow. You may need one in the winter. It does not get much below 40 here during the day and cruising with no load I see around 125ish.

I have a 2005 Silverado 3500 and the stock cooler is marginal for towing in the mountains in the summer. I first installed Mag Hytec pan and synthetic fluid it helped but when pulling on route 89 south of Stowe, VT on a 95 degree day with very high humidity, the transmission temp got over 200 degrees for a short time. I did some research and many people driving with a 4L80E are using a Tru-Cool 40K as a replacement for the stock cooler. When towing now the transmission temp runs about 160 degrees. As far as overcooling, the fluid is preheated in the radiator and the Tru-Cool has a provision for thick cold fluid or you can add a thermostat. It is my understanding that the thermostat actually makes the transmission run warm.
My reason for upgrading is that we are now retired and going to visit many national parks and they are in or around the mountains.
Good luck.