Transmission cooler for Chevy truck

I want to install a transmission cooler for a 2000 Chevy Silverado w 5.3L w/ 4L60E. I googled how to do this and there's a lot of
contradicting info. Some say get the largest cooler you can and completely bypass the in-radiator cooler. Others say go trans to radiator, radiator to cooler, cooler back to trans. Then some also say go trans to cooler, cooler to radiator and then radiator back to trans. I guess this method is to "preheat" the trans fluid in cold temps? I have not seen any mention of a thermostat other than operating a fan on the cooler itself.
Do I even need a cooler? I am in the Denver area and tow a 7000lb trailer 500-1000 miles a year, mostly in the summer. I read the 4L60E has cooling issues so I never tow in OD and change my fluid/filter every 20k miles. If I do need one, can I just bypass my radiator completely? On an old Buick, the internal radiator trans cooler leaked and circulated trans fluid through the cooling system which was the beginning of the end for that car and I'd like to avoid that on my truck if it's safe to do so.
TIA!
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My opinion....I like plenty of tranny cooling...
Data shows clearly ( and you can find it on the web) that overtemperature operation will kill an automatic transmission in a very short time period. Minutes to hours, depending on the degree of overheating... and since you tow a trailer, you may be subject to overheating at some time or the other.
I think an external cooler is a pretty cheap bit of insurance.
I used to run one when I was towing a camper, and I think it extended the life of the crappy 440T4 tranny (which eventually failed...most of that group DID eventually fail, at about 100K).
I figured that if I used two units, or one external unit and the radiator internal one, it might be best to run them in parallel...Less resistance to flow than running them in series.
I dont think you can argue successfully that the tranny needs the heat from the radiator, but have been wrong before, and am sure I will be again..
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genius wrote:

I have a 2002 Astro with the 4L60E (I'm pretty sure). Different engine (4.3L?), different radiator (probably), and my trailer is only 2000lbs, so this may not be relevant to you. I had tried the cooler option on a previous vehicle, and elected instead to use temperature gauges on the Astro, rather than cut into all that nice metal tubing. I made some aluminum blocks into which I threaded the temperature senders. I drilled a hole the OD of the tubing in the other half of the block, and then sawed this hole in half so that I could hose clamp the block to the tubing an get good contact. I put one block on the transmission inlet and one on the outlet, both close to the transmission. This way I can see both the inlet and outlet temperature. I also added a light near the gauge that indicates when the torque converter clutch (TCC) is activated (torque converter locked).
The Astro has a Tow/Haul switch that makes the transmission keep the torque converter locked most of the time. This really cuts down on the heat generation. The main problem is that the Astro/transmission does not lock the TCC at any speed below 27MPH (at least that is what we found).
We towed through the Rockies in 2004 (Badlands, Yellowstone, Tetons, Dinosaur, Mesa Verde, RMNP, etc.). As long as we could keep the speed above 30MPH, and thus the TCC locked, we never had any trouble with over-heating (temps always below 230F). There was one section of CO139 (maybe at Douglas Pass) where the road was both steep and curvy forcing us below 27MPH, and a section of CO145 at Lizard Head Pass that was under construction and slow. In both cases, with the TCC unlocked, the transmission heated rapidly and we had to stop to let it cool.
So, you might choose the temperature gauge option if you don't mind the occasional stop; or you might want more cooling if you never want to stop. Either way, one gauge on the transmission outlet might be comforting. I certainly hope your truck has more factory cooling capacity than an Astro.
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