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Thread: H2 external tranny cooler

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    H2 external tranny cooler

    Just installed the H2 external transmission cooler and completely by-passed the radiator internal cooler. Now i don't have to worry about the coolant mixing with transmission fluids when the radiator internal cooler go.


    I used this http://www.amazon.com/gp/product/B00...ilpage_o04_s00


    Also, did this:
    replaced transmission filter, transmission pan and gasket (old pan we're dented from off-roading)
    completely flushed the transmission fluids with oem dexron 6 and reset transmission fluid life to 100% with Tech 2
    replaced transfer case fluids with oem dexron 6
    replaced front and rear differential fluids with oem 75w90 synthetic gear oil
    replaced rear brake pads and parking brake shoes


    Serviced front brakes
    Need right rear parking brake cable, siezed, parts on order.


    Road test result with the new external cooler (about 20 km distance), will update for long term use:
    54*C at idle with 90*C engine temp.
    65*C at 110 km/hr with 28*C outside temp


    I used to run around 98*C with the stock tranny cooler.
    I will see if i need to install the by-pass valve in the winter.














    2008 Hummer H2 Luxury Package

    Toyo MT 38x13.50x18 on Rockstar. Green keys. 2" rear spacers. 1" bodylift. Cognito UCA, steering bracket, front stab links. Bilstein 5100 shocks. Moog inner/outer tie-rods, pitman, idler arm & bracket with remote zerk. E&G Classics fender flares. ARP 434-1301 ex. man. stud kit. Airaid perf. air filter. Crown Performance brake lines. Warn PowerPlant HD. Rubberduck UCP. Gobi Ranger Roof Rack. Morimoto FX-R 3.0 projector headlights with 55w AC HID kit. Hella Rallye 4000 aux lights. Evans waterless coolant.

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    Re: H2 external tranny cooler

    That's a nice clean install on a good and dirty truck!

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    Re: H2 external tranny cooler

    thanks guru, i think you need to install one too in your newly acquired sut.
    2008 Hummer H2 Luxury Package

    Toyo MT 38x13.50x18 on Rockstar. Green keys. 2" rear spacers. 1" bodylift. Cognito UCA, steering bracket, front stab links. Bilstein 5100 shocks. Moog inner/outer tie-rods, pitman, idler arm & bracket with remote zerk. E&G Classics fender flares. ARP 434-1301 ex. man. stud kit. Airaid perf. air filter. Crown Performance brake lines. Warn PowerPlant HD. Rubberduck UCP. Gobi Ranger Roof Rack. Morimoto FX-R 3.0 projector headlights with 55w AC HID kit. Hella Rallye 4000 aux lights. Evans waterless coolant.

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    Re: H2 external tranny cooler

    Quote Originally Posted by citiboy View Post
    thanks guru, i think you need to install one too in your newly acquired sut.
    I'm a little leary of those big ones now. I had that same setup in the SUV and when a sheet of ice came through the grill on a (too fast) dip in a frozen mud hole it pushed part of the radiator support back and clipped off the hose connector on the bottom, passenger side of the cooler. Needless to say, I had a nice puddle of tranny fluid on the ground and we were off to the auto parts store for a new cooler. Ha!

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    Re: H2 external tranny cooler

    well, if that happen to mine, i can easily return the tranny line to a stock set-up by removing it from the external hose and just push it in to the radiator cooler.
    2008 Hummer H2 Luxury Package

    Toyo MT 38x13.50x18 on Rockstar. Green keys. 2" rear spacers. 1" bodylift. Cognito UCA, steering bracket, front stab links. Bilstein 5100 shocks. Moog inner/outer tie-rods, pitman, idler arm & bracket with remote zerk. E&G Classics fender flares. ARP 434-1301 ex. man. stud kit. Airaid perf. air filter. Crown Performance brake lines. Warn PowerPlant HD. Rubberduck UCP. Gobi Ranger Roof Rack. Morimoto FX-R 3.0 projector headlights with 55w AC HID kit. Hella Rallye 4000 aux lights. Evans waterless coolant.

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    guruerror (09-01-2015)

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    Re: H2 external tranny cooler

    Quote Originally Posted by citiboy View Post
    well, if that happen to mine, i can easily return the tranny line to a stock set-up by removing it from the external hose and just push it in to the radiator cooler.
    Genius...I don't know why we didn't think of that?!

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    Re: H2 external tranny cooler

    That's a super clean install !!!

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    citiboy (12-11-2015)

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    Re: H2 external tranny cooler

    Wow very nice and clean install, I'm gona start this same cooler install, but ONE Question,,,,,, I saw that air could be trapped in the cooler with it connections placed in the down position, ------does this cause any issues????---------- I see where routing the cooler lines up on top would be tricky. Still up in the air about witch way to go....I'm gone play with things for awhile and see what fits best.... I'm gona try to keep the orig. trans lines stock. (but we'll see)

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    Re: H2 external tranny cooler

    I don't think air could cause a problem the cooler should partially drain when parked anyhow, I've had mine on for about 60k miles and it never goes above 155 F. Just make sure your lines aren't in the way of anything on the engine, or close to anything that gets hot, or if they sit on other lines or metal add a layer of padding to the hoses to keep hoses from rubbing through. Make sure your lines are tightly connected, I failed to properly double flair my transmission hose (metal) which happened to start leaking out on a trip in the mountains covering my back window with a nice film of transmission fluid. I still haven't properly Flaired the line I just added a second clamp to it...

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    Re: H2 external tranny cooler

    I wanted to ask, after looking at the pics, the lower tranny line on the rad. is coolant line from trans and cant I just unplug it from rad and with the barb attach a rubber hose there to the new cooler.... and for the return connect a rubber hose to the pipe that connected to the old cooler? (on the driver side).. I am also using this TRU-COOL trans cooler and have noticed the tight clearances. SO to surmise id really doesn't matter which way the connections are. Ill post some pics of how it turns out.. tks again

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    Re: H2 external tranny cooler

    as iwillnc has already said and done... it doesn't matter how sure you are with the clamps on the lines... add a 2nd one.
    I went a step further and marked the lines so I can see if there is any movement.

    I had a line pop off multiple times while driving. all times I got lucky and was able to make it to a gas station to clear out their supply of tranny fluid.
    in the winter time it looks like I hit a deer or something with all the red fluid under the front end. and yes, it does suck trying to tighten clamps in the middle of winter when the temps are -14.. which is a mild day here in Minnesota :)
    2003 Black Hummer H2 Adventure Package
    4.88 gears *** Cognito UCA & SwayBar Links *** Kryptonite tie rods *** K&N CAI *** 37x12.50xR20 BFG KM2 Mud Terrain's *** 20x10 Black KMC Rockstars *** EBC Slotted Rotors *** N-FAB Sidesteps *** Line-X Grill *** Recon Smoke Cab Lights ***Diablo Predator U7193

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    Re: H2 external tranny cooler


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    Re: H2 external tranny cooler

    Here's what I did today, install went pretty smooth, following what was previously said I paid attention to the top and far left side (pass. side) of cooler location. because its a big unit. tips that I did were #1 before bending the top pass mount I cut a line down so that I could better grasp and bend the tab over, then cut off the unused portion. (top and bottom run does NOT carry fluid, but still be careful) #2 when Trimming the pwr steering cooler mount, I made two cuts from left to right and then bend them over out of the way. see pics, much easier . for all cuts I used a 3in cutoff wheel. Just be super careful around the other radiators. -use a barrier of some kind between yr work and material- -cardboard or sheet metal- and I used some cheep rubber caps from auto parts store to seal pipes and fittings during install. (kept every thing MUCH CLEANER) . no pipe cutters were used during this install. Factory pipe has a single barb which I used along with two clamps . I disconnected the pipe that went into the bottom of radiator and ran a line to the new cooler, (I had a piece of heater hose sitting around so that went on this hose to the lower hose where it went through radiator support. I connected the return line from cooler to the pipe I disconnected from original cooler.. NOW I left enough hose on the bottom of new cooler so that it can be unbolted and leaned forward and the HIGH point is on the bottom and this will bleed air out of system, ( don't know the science of fluid being able to flush itself or not. hope this helps.

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    Re: H2 external tranny cooler

    ***Update***

    2008 Hummer H2 Luxury Package

    Toyo MT 38x13.50x18 on Rockstar. Green keys. 2" rear spacers. 1" bodylift. Cognito UCA, steering bracket, front stab links. Bilstein 5100 shocks. Moog inner/outer tie-rods, pitman, idler arm & bracket with remote zerk. E&G Classics fender flares. ARP 434-1301 ex. man. stud kit. Airaid perf. air filter. Crown Performance brake lines. Warn PowerPlant HD. Rubberduck UCP. Gobi Ranger Roof Rack. Morimoto FX-R 3.0 projector headlights with 55w AC HID kit. Hella Rallye 4000 aux lights. Evans waterless coolant.

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