UR opinion, extra transmission cooler..

Sure it's not a AC cooler?

Has your trans fluid been running hot? If not then the engineer's rule applies: "if it ain't broke don't fix it!

Nope you don't need it. And to be honest. You want the transmission running at temp. Too cool can be a problem. could keep the trany from changing gears correctly. They change differently before they warm up, at least mine does. Won't go into OD before it warms up.

bgum wrote:
Sure it's not a AC cooler?

It's definitely a factory auxiliary transmission oil cooler. The condenser is a great big thing and, this vehicle has a power steering oil cooler as well, OEM. I think I will leave it alone. The transmission runs cool, as far as I can tell, no problems with it and I keep fresh Dex-6 in it. I ground down the factory drain plug, that rounds off and works for no one, and welded an 11/16 nut to the plug. Now doing a simple drain and fill of the transmission takes 5 minutes.

I'd do it...and put it in parallel to slow down the fluid 'in' both plate type coolers...therefor better heat rejection

But, gotta keep it plumbed back into the main radiator cold tank to re-heat the ATF during extreme cold weather

I would return the cooler and stick with OEM. Partially because IMO any additional fittings or rubber hoses present additional risk of leaking. As long as you have the OEM cooler with steel lines and flare fittings I would not bust into it.

If concerned about the transmission consider a fluid exchange with synthetic fluid if you have standard fluid in now that has some miles on it.

I would not add it unless you know for a fact it's getting too hot. You can over cool the fluid.

I added a second one to my last truck, it appeared to make no difference at all, except that I did end up with a repeating leak.

I am towing at or over the rating of our Yukon, so I added a cooler in line with the factory cooler to help keep the transmission temp down. To mount them, I bolted strips of aluminum in front of the radiator one at the top one at the bottom. Moved the oem cooler to the passenger side and mounted the new one on the drivers side. The new one has an electric fan that I wired to an adjustable thermostat. I can definitely see lower temps when adjusting the thermostat down.
The engine oil goes through the drivers side of the radiator, I have though about putting a cooler on that line as well.
If you don't already have one, you should get a guage to monitor the trans temp. A scan tool would work, or a tuner with a display (Bully Dog, Diablosport, Edge)
Also, from what I have read online, the overdrive gear in the 4L60 should not be used when towing. Wish I had learned that before killing one lol.

Swap out your gauge cluster for an HD cluster, and you'll now have a working trans temp gauge. Use that as a guide as to whether or not you need to install an aux cooler.

I pulled trailers as heavy as 7,000 lbs with my '01 Suburban 1500, and never saw any trans temp that caused me concern. And that includes towing in the Rockies.

And yes, avoid 4th when towing. 3rd is a 1:1 ratio, so it puts the least stress on the transmission. Took a little while to get comfortable with the engine at 3000 RPM while cruising, since the truck had 4.10 gears. But I logged over 15,000 miles towing like that, and the truck now has 235k miles on it with the original engine and transmission.