I know many have had issues with the transmission cooler line that is inside the radiator and prone to failure on 07 and older H2's and GM trucks. When they fail coolant is introduced into the transmission which promptly destroys it. This generally occurs after the 100k mile mark and one of the reasons I replace the one in my 06 at 130k. After replacing it I cut the 06's radiator apart I noticed the trans cooler line inside the radiator was in poor condition and I was happy I replaced it.

I was wondering if the same issue exists with the 08/09 considering they use a different part number then the 03-07 H2's. Funny thing is the radiators for the 08/09 are about twice as much a the previous generations. Makes me wonder if GM made some improvement to the materials they used and if they are still an issue on high mileage vehicles. Anyway, I am getting close to the 100k mile mark I would rather replace it then wait for it to fail and destroy my trans. Then again, I don't want to waste money if it isn't necessary.

Comments, suggestions always welcomed!

 

08 Owner here.
08-09 have separate transmission coolers in front of the radiator. So no issue there I don't think.

 

Ahh, so you bypassed your original integrated radiator cooler for an external unit. I would consider that but it gets cold here during the winter. I need the heating the radiator provides to the trans fluid when its real cold and your just getting underway.

Your external cooler is an excellent solution in warmer climates! Thanks for the suggestion.

 

No actually I believe it’s factory that way. However after reading, some say there is an external one as well as being plumbed through the radiator. I’ll have to look tomorrow and verify.

also I would suspect that since the 08-09 engines are all aluminum there would be less of a chance of rust or corrosion eating away at the radiator.

I’ve been looking into upgrading my cooler, but I can’t find any good kits online. My trans can easily get over 200 on a hot day or even sit at around 220-225 when pulling a trailer. Gm claims that’s normal and the fluid is rated for it, but it makes you wonder why the failure rate is so high on these transmissions.

 

Your right, the 08's and 09 had factory coolers as well as a cooler inside the radiator. I went out an checked mine, tucked behind the power steering cooler there it was, an external trans cooler. I made a phone call and according to an old H2 Mechanic I know at my local Cadillac dealer, the 08 and 09 needed an external cooler because of the additional heat of the 6L80 trans and the L92 engine. This was also done because that GM up the factory towing rating for the 08/09 which was a standard option.

For what its worth I had an 07 Escalade with the same engine and trans and use to pull an 7000k travel trailer with it and had the same issue as you are having. After a summer of towing the trans took a dump even though I replaced the trans fluid well more then was required. When I had it replaced I was told anything much more then 220 is the danger zone which mine use to see 230 in the heat of the summer. I was also told that if the transmission is high mileage high temperatures will quickly take it out as mine died with 60k on it.

After the trans was replaced I installed a Derale remote electra cooled transmission cooler under the vehicle and never saw temperatures over 190 degrees even with the trailer in the heat of the summer. It was a nice setup and the fan did not come on until the trans temperature required cooling.

If I towed with my H2 I would seriously consider it especially when you consider your trans will cost you about 4k to replace if it dies. Summit is a great source for just about any kind of cooler you want to add to your H2.

I still have yet to find any good answer about the radiator issue, It would be nice if there was a way to find out how many radiator failures GM had on the 08/09 Model year. But that's probably top secret info only a GM insider could find out.

 

Man That sounds awesome. I am definitely going to do that. Do you have a part number for which one you used? There seem to be a few different ones available from summit. Also where did you mount it? If you wouldn't mind, could you take a picture of it?

Edit: It just hit me your h2 is the only other solar flare metallic one I've ever heard of. I'm sure more exist but its very few!

 

Hi Gavin, My 07 Escalade is long gone so I can't share a photo of the installation but what I did was tap into the return line going back to the trans and installed the Derale 15900 (summit part no 259-15900) just under the radiator support in the front. If I was going to install one of these today and since I don't have the rear air suspension option there is a great space at the rear of the H2 where GM normally mounts the air compressor, that's where I would put it. It would be too big to mount anywhere in the front. Since the cooler kit is fully contained, simply plumb it it, hook up power and your set. It has a built in temperature sensor and will only cycle the fan as necessary. Summit was super and their tech support was able to provide all the fitting and parts that were necessary to install it. Cost wise it wasn't bad and under $200. with all the goodies. If I was towing with my 08 H2 one would already be installed in it.

Funny story about my 08 Solar flare, I always loved that color and really wanted an 08. Trolling the internet last year I stumbled across it at a dealer in Florida that had one, I had an inspection company go over it and bought it without ever driving it. Shipped it back to New Mexico and sold my 06 H2 Adventure in 2 days. About the only thing I miss from my 06 was the rear air suspension but it was a small thing to give up. I just love the 08, and the color is a real contention point, Ive been to a few car shows that some argue its called inferno orange even though the brochure for the 08 model year calls it Solar flare Metalic, all I know is I just love it and they didn't make many of them in that color. Happy motoring and good luck with your project.

 

Thanks. Mine was a Florida car too. And It is definitely Solar flare. Inferno was on the vettes and camaros.