Is Transmission Cooler in Main Radiator Needed if I have Two

I have a 1999 Chevy Tahoe with the tow package. It's rated to tow up to
6,500 pounds. I usually do not tow but I periodically tow a 3,000 pound boat or a 5,000 pound travel trailer (not both at once, of course!). It had a single external transmission cooler until a couple of months ago.

Long story made short: Transmission shop recommended and installed a second auxiliary transmission cooler -- for a total of three coolers including the one inside the main radiator -- because they suspected excessive transmission heating. A couple weeks later while towing the travel trailer the transmission failed (as in only neutral "worked", and a lot of transmission fluid was found in the engine coolant overflow reservoir.
Tranny shop bypassed the transmission cooler in the main radiator since it appeared to be leaking. So now I am not using the transmission cooler part of the main radiator and am instead using the TWO external transmission coolers. Transmission shop said I'm good to go now and suggested I stay away from using the main radiator's transmission cooler because a leak can ruin the transmission (as it did!). By using ONLY external coolers I'll never have to worry about THAT happening ever again, they said.

I took it to a radiator shop for a second opinion from their perspective.
They said the transmission cooler in the main radiator is needed if I will ever drive in a cold climate because that is the only "cooler" that will actually *warm* the transmission fluid when needed. They also said that a leak in the main cooler is extremely rare, so I really shouldn't worry about that happening again once the existing main cooler is replaced.

So now I'm wondering what to do. My options are:

1. Leave it the way it is. Use just the two auxiliary transmission coolers and bypass the transmission cooler in the main radiator.

2. Replace the transmission cooler component of the main radiator and put it back in series with the two aux coolers. With this I'll have three tranny coolers as well as the risk of a future leak costing me another $2,500 in transmission repairs.

3. Same as #2 but disconnect one of the aux coolers (one person suggested to me that three coolers is not a good idea but I don't know why).

What is your opinion? I live in a mild climate (Portland, Oregon) where it is usually above freezing and rarely more than a few degrees below freezing, but I sometimes do drive in the winter-time to much colder places (without towing).

I have a second question which I'll post separately.

leave it as is

the fluid coming out of the converter is usually at 200 , and doesn't need 'heating'

It would be interesting to know the temp of the return line after going through an auxillary cooler first then exiting the radiator tube, on a cold winter day.
Anyone ever done this? Even better would be 3 temp senders - Output from trans, between the coolers, return to trans. Toggle switched to one gauge.
Rex in Fort Worth

Conversely, if it resides in a cold climate, the transmission needs that heat to warm up properly. In the southern tier of states, I would also not bother.

by that line of reasoning, you should never start it below 30, cause you'll kill it before it warms up............

As I stated in the other post, you need to have the radiator guy clean and test the radiator and hook all those lines back up. If the transmission fluid didn't need warming in cold weather the auto makers would never run the lines through the radiator. You can listen to others that have never built a vehicle, or put it back the way it was built. Never before heard of needing 3 coolers in a line UNLESS the radiator was partially clogged.

FWIW: Because I have a huge aux. cooler in my class A, (The previous owner apparently needed it). and I don't tow anything, and never drive in high mountain terrains, I was concerned that maybe my tranny oil was not getting hot enough. So I asked Valvoline what was the "LOW" temperature limit on transmission fluid, under which operating a vehicle could damage a transmission. The answer I got was , and I quote: "... 30F.)

The answer was very short, with no other explanations. It leaves me to wonder if maybe, I did not ask the right question, or if there is more to it than that.