Transmission cooler, best type and place to put it
 

I am looking to add a transmission cooler to my 06 SUT. Perhaps a Derale powered cooler would be a good choice but there does not seem to be a good place to put it.

Suggestions, and, how well did it work. I would like to do some towing with the H2 and the trans runs just under 200 on the gauge when the coolant is hot. I also thought a 160 degree thermostat might help as well.

It gets really hot here in New Mexico and every little bit helps.
Thanks

There are multiple threads on adding a tranny cooler. Using the search function will yield those results.

Very True, but unfortunately there is no hard info to be gleaned from those threads. Some talk about duramax, cam's, different model H3's. Everything but what I am searching for.

What I am looking for is info specific to the H2 SUT and the 06 configuration with 4l65 and 6l not the later 6l85 and 6.2 and the reason I created the thread

So far a possible solution is a Derale 13740 remote mount trans cooler with inline temperature control and dual fans to keep the fluid right around 180 and possibly a multi core aluminum radiator with factory clutch fan. This trans cooler can be mounted anywhere in the vehicle that ill not be in direct line of air flow so tucking it underneath the vehicle inside the frame rails could work. The only consideration would be to place it where I could not be damaged from passing over brush. It might need some type of shielding. Jury is still out though.

One thing I found interesting is that Derale recommends that trans fluids should be close to 180 as that is optimal and causes the least wear to the transmission. Obviously more homework is needed, perhaps I need to look at the other Hummer forums as well.

Our setup is near identical to the GM trucks and SUV's..... many on the trucks have installed the Tru Cool 40k
This is a massive thread on Performance Trucks about it. I have not measured if the custom brackets on guy on there makes would fit on our H2's. https://www.performancetrucks.net/fo...thread-470284/

Either way that is what I'm going to be installing on my H2 to replace the tiny stock one at some point. When I do I'll also be bypassing the radiator cooler to 100% eliminate the risk that the baffling in the radiator might fail.

MixManSC,
Thanks for that post and very helpful information. Great pictures, I knew our H2's front clips were derived from the 2500 GM trucks but surprised to see how close they really are. That said I wonder if aftermarket radiators for the trucks will bolt right in or is the sheet medal/front cap different enough to prevent that. (a becool would be nice, more homework required). One point I would like to bring up, I contacted Derale about the 13740 remote cooler and told the tech I wanted to bypass the lines in the radiator when I install a remote or aux cooler. I was advised against it. He told me that trans temps under 170 are as bad as very high temperatures. As it was explained cold transmission fluid is very abrasive and that fluid around 170 actually provide the best lubrication for the trans.

I was very surprised to here this as I always was under the impression you wanted your trans fluid to always be cool (not cold). Comments welcome on this.

On the Tru Cool 40k they have one with or without a bypass. The bypass is to help warm the fluid when it is too cold. The truck folks pretty much agree that if you live in the deep south where it rarely gets below freezing you are fine to go with the slightly cheaper version without the bypass. That is actually the function of the fluid going through the radiator on our H2's and the GM trucks. That part of the setup is to help warm the trans fluid. Otherwise you want to get a cooler with a thermal bypass. When I do mine later this year, even though I'm in hot as ba**s South Carolina, we do sometimes get some brutally cold temps in the 20's so I'll be going with the version that has the thermal bypass. Oddly I hear many stories on here about the factory radiator divider failing which allows coolant to mix with the trans fluid (which is very bad and will destroy your transmission) but the GM trucks which use the same radiator you do not often hear about that issue and many who add an aux cooler leave it going through the radiator (which negates the need for a thermal bypass). I think we hear about the radiator failures a lot simply because those who have a major problem tend to be the loudest and post about it while the other 99% of the vast majority have no reason to even think about that happening because in truth, it is quite a rare occurrence.

On my GMC truck that I am in the process of doing a major overhaul on, one thing I'm doing on it is adding the factory aux cooler since it did not come with the factory towing package and therefor did not come with the stock aux cooler. I'm simply adding the stock aux cooler to it (pretty much identical to the one on our H2's) and that is it. Even with towing on occasion and driving it since 1999 I've never had any issues. Main reason I'm doing it is for peace of mind, secondary is I'm adding nearly every possible factory option for the truck that is did not come with as part of the project. Actually just finished adding the cooler the other day and started it up for the first time in over a year....

MixManSC, were you going to remote mount the Tru Cool or try to put it in front of the radiator?

At one point I owned an 02 Silverado 2500HD with the 6L and 4L80 trans. The trans in that was far superior to the 4L65 used in our H2 and never seem to get over approx 175. If my 4L65 craps out I will seriously think of upgrading to the 4L80. I have been closely monitoring my temperatures and the trans follows the water temperature, bypassing the radiator in itself and adding an aux cooler would take care of the trans heat problem but we have cold winters here in NM so that is not an option.

My other issue is if I did mount the cooler in front of the radiator how much would that effect the airflow to the radiator? My water temperature averages around 205 without doing any towing and that's with a 186 degree thermostat, AC on and outdoor temps in the high 90's. Unfortunately since the trans fluid runs through the radiator it gets heated as well. I have a feeling my solution will end up being a remote forced fan transmission cooler and a new extra capacity radiator.

I just completed a full flush on the radiator and engine with a 50-50 mix of dexcool. The radiator was replace by the previous owner with a typical oem style replacement and is in good condition. I am leaning towards implementing the forced air remote trans coolers and seeing what the results are. I would hate to have to scrap a perfectly good relatively new radiator for an expensive multi core performance unit but that may be the only answer.

Anyone who has input or completed upgrades of this time please chime in. Thanks

The stock trans aux cooler is already mounted in front of the radiator..... it is just tiny and insufficient under much of a heavy load. Placing the aux one in the same location, while it is larger, will not hurt engine cooling at all as the trans fluid will also be cooler which puts less heat into the engine coolant. This is how trans coolers are almost always installed as well as intercoolers for both turbo's and superchargers. As far as the trans fluid going through the radiator - bypassing that is also not an issue as long as you get an aux trans cooler that includes a bypass. The bypass is thermal and serves nearly the same function. When it is below a certain temperature it just diverts the transmission fluid directly back to the transmission. That will allow the heat in the transmission to more quickly build up in the fluid. Not quite as quickly as if heated with the hot engine coolant but on a cold start the engine coolant is also ice cold.... In your scenario, if it were me, I'd trust that the replacement radiator is fine and leave it going through the radiator which helps warm the fluid in very cold temps, and just replace the stock trans cooler with a better larger one. Specifically, the Tru Cool 40k that does not have the bypass (since it will still go through the radiator). More info on the Tru Cool coolers - Tru-Cool Transmission and Engine Coolers: Protect Your Vehicle. Save Your Money. | Tru-Cool Tru Cool also recommends against bypassing the radiator in their FAQ's as well.

On my GMC truck, I am leaving it to still go through the radiator as well.

On the GM trucks - the Tru Cool is the most popular one.
This is the one that comes with a thermal bypass This is the same one but without the thermal bypass /

This is a big thread on performance trucks where a LOT of people have done this exact mod on the GM trucks.
https://www.performancetrucks.net/fo...light=tru+cool

Now - that being said. While the Tru Cool Max LPD 40k cooler is an awesome cooler. On our H2's it has some fitment issues. @Maxjeep has installed on on his and it appears as though the 22" width is a bit much. Even installing it as far to the left as possible it looks like the power steering cooler bracket would still be in the way and need to be modified to make it fit. https://www.hummerforums.com/forum/h...2-41294/page3/ He might be able to give us a little more insight on that. Only thing I dont like on the way he mounted it was using the EMT conduit as a spacer - that is going to rust. I'd have to come up with an aluminum spacer of some sort. The 6an type fittings and braided hose are top notch but not really required. If you use a tubing cutter (like a plumbing style one for copper tubing) you can cut the factory hard line in a clean smooth straight spot and use a 3/8" brass compression fitting to 3/8" barb to connect some basic trans fluid hose. One thing that is critical - the hose needs to be the proper type for hot transmission fluid. Fuel line is NOT acceptable nor is just any other random tubing. You can get a 3 foot piece of it at Advance Auto parts for about $10 but the Tru Cool trans coolers also come with some as well which might be enough. Another thought is one of the other models from Tru Cool would also likely be plenty enough better than the stock trans cooler, the problem on our H2 is the are for installing one is limited in space. Can only be at most about 1.5" thick, x 9" tall x about 20" wide. The True Cool Max 40k is 22" wide which is why I think Maxjeep ended up modifying the power steering cooler bracket.

MixManSC, what you point out makes a great deal of sense. I never really looked closely at the small cooler in the front thinking it was a powersteering/hydroboost coolers. Shame on GM putting such a tiny trans cooler in a vehicle that weighs over 6k with a substandard 4L65 trans especially for what the H2 sold for new.

After reading though the threads you provided for the sake of simplicity the true cool seems the ticket and provides the best bang for the buck. I am hopefully that it will remove some of the load on the radiator like you mentioned resulting in lower coolant temperatures. Perhaps Maxjeep can chime in here on his experiences. I am surprised he did not dump the factor cooler and simply center the Tru Cool, I guess the added capacity helps as well. Thanks again for the detailed response and attachments. This makes the job so much easier. Cheers!

He did get rid of the factory trans cooler but not the smaller one for the power steering. Problem with the little power steering/hydroboost one is that is will not allow the Tru Cool to fit unless you either move the PS one further to the right or in some way modify its brackets which is what Maxjeep appears to have done.