Is everyone just using an OEM rad? If not what brand is the best for replacement? I've got an 05 and I've been doing all the 100K maintenance lately.

Great information, many thanks!

I'm going through my 2007 H2 and came across this last night. So I'm assuming the small cooler in front of the radiator is an oil cooler then? I'm original owner and I don't remember adding anything to the cooling. I attached some pics. Also, I ordered the two volume repair manual in November from ebay, still don't have it (on Backorder). So I'm a little in the dark until it arrives :confused:

If your the original owner and you haven't added it. I believe that is your power steering cooler.

Mine has two coolers (03). Power steering and trans. The trans internal cooler was bypassed and made external by the PO.

I also check my 2003 Hummer H2 and found that there are two smaller coolers or radiators in front of big main radiator. One cooler or radiator is smaller and second one is the smallest. What are these smoller radiators for? I didn't add any radiators by myself. May be previous owner did it but that time I purchased the truck mileage was around 100,000km. Any ideas?

most likely they caped off your internal lines in your radiator. transmission cooler and engine cooler lines.and added these externaley. these are just my thoughts on this.

So do You think that previous owner did good job for me and brought outside those transmission cooling lines?

I've seen a few people post on here that the internal trans cooler let go inside the rad and flooded there trans with coolant and destroyed it.

Personally I would rather it be external.

So,is the originally installed transmission cooler should be inside the main radiator? I've got from previous posts that some guys had troubles with that design, so that's why many people put transmission cooler outside main radiator to prevent from breaking it down and and polluting main big radiator or wise versa.So what kind of coolers are outside of main radiator in my case: transmission cooler and oil cooler?

Since I'm running the factory setup on my 2007 H2 and I have about 120k miles, I think I will do the external trans cooler. I would also like to change the radiator to a new one that doesn't have half of it used for cooling the trans fluid. I live in AZ and the more cooling the better.
I've read a lot this past week about Dex-cool and the corrosive properties. The plus side with Dex-cool is that it lasts longer (about 75k miles) than the conventional coolant (30k miles). You can change out the fluid, but you need to do a really good flush to get the dex-cool out. Then you need to change the coolant every 30k miles. There is also a possible class action lawsuit vs GM concerning the Dex-cool corrosion problems. You also need to wait until you are out of warranty to do it, as I'm sure it will void it if you change coolants.

I believe one is a transmission the other is power steering. A member (MadMayo) stated that is what he has. Not sure if they have external oil cooler for the engine? I guess if you have the money anything is possible :D