Radiator (internal) transmission cooler bypass?

Jeepwalker said:

The beauty of the factory system is it's simplicity. Now there are 3 additional points of weakness:

1) A lot of rubber hose that are prone to burst or leakage: Or maybe you plan to go back and bend steel lines with flaired or brazed ends when time permits. Seen a number of leaks in my day. Course most of those were older hoses.
2) A bypass that can fail (hopefully it fails 'open')
3) Airflow impediment.

Not cutting down your work or efforts, just pointing it out. I get what you're trying to achieve. Thanks for raising the awareness and sharing alternative ideas. If you don't run into overheating issues, that will be great. If your AC doesn't perform as well, try moving the cooler.

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Definately good points, some I did take into account when I installed my cooler. I’m always open to critic. My main concern was temperature; temps were creeping up to 240 F and I knew that wasn’t sustainable for the life of the transmission.

The plan has been to reinforce the cooler lines with either heavy duty line or metal line, just haven’t had the time just yet.

The thermostat I bought I believe can either fail open, or fail closed. This is why I kept my internal trans cooler and ran it in series. If that day ever comes, I have OEM cooling. In addition, the radiator was replaced 3 or so years ago. I’m not worried about it failing just yet.

As for airflow, I currently have a HD clutch fan and pusher Efan. This setup works great but as this is becoming a side truck, I’ve been in the Process of installing an electric fan setup to be better setup on trails and city driving (I do a lot of highway and short trips. But will be moving to a much hotter climate).

alrock said:

Looking back at my notes, the ID of the trans lines is 3/8 so I doubt that your hose size selection is the issue. Is there a chafing spot on the hoses where it may have split? Are the hoses that you are using transmission line hoses? Maybe another brand would do better. I'm guessing here, I don't have a good answer for you.

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No chafing where it split. I used Derale 3/8" Automatic Transmission Oil Cooler hose the first time around. I believe it was Hayden 3/8" Automatic Transmission Oil Cooler Hose from O'Reilly the second time. I was thinking about switching to braided stainless steel Transmission Oil Cooler Hose, but don't want to mask the issue and cause a bigger problem down the road. Knowing you used 3/8 hose with the same cooler leads me to believe that there's either an issue with the cooler itself, or the thermostat.

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My main concern was temperature; temps were creeping up to 240 F and I knew that wasn’t sustainable for the life of the transmission.

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That's true ...this was a good way to tackle high temps. High temps can kill a tranny...

How fast is it happening? If in a small period, why not go trans-tstat-radiator instead of cooler. See if the line blows up. If not then probably the cooler is the issue.

Jeepwalker said:

The beauty of the factory system is it's simplicity. Now there are 3 additional points of weakness:

1) A lot of rubber hose that are prone to burst or leakage: Or maybe you plan to go back and bend steel lines with flaired or brazed ends when time permits. Seen a number of leaks in my day. Course most of those were older hoses.
2) A bypass that can fail (hopefully it fails 'open')
3) Airflow impediment.

Not cutting down your work or efforts, just pointing it out. I get what you're trying to achieve. Thanks for raising the awareness and sharing alternative ideas. If you don't run into overheating issues, that will be great. If your AC doesn't perform as well, try moving the cooler. In Dallas, you need the condenser to be able to reject heat as efficiently as possible. Just a little reduced condenser efficiency can have a big impact on your cooling. It's not linear. (I work in HVAC).

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My rig is 10 years old with 75K miles. I’ve read of multiple H3/H3T owner’s who've had their internal transmission cooler fail about this time, and they end up having to replace the radiator, and the transmission in the process. That’s what I’m looking to avoid.

I weighed the pros and cons of adding an external trans cooler and bypassing the internal one in the radiator; 1) air not as efficient at cooling as liquid, and 2) added time to bring trans fluid to proper operating temp. I went with an oversized, stacked plate, transmission cooler to address less efficient cooling, and placed it in a location to get maximum air flow. And I installed a 180 degree thermostat to help bring trans fluid to proper operating temperature quicker. With regards to the trans cooler restricting airflow, or heat dissipation of other cooling elements (condenser, radiator), I thought about it. However, with everyone else out there currently running external trans coolers, and nobody reporting that as being an issue, write or wrong, I figured the impact to be minimal.

I did purchase an OBD-II Adapter (OBDLink MX), and the Torque Pro app, so I can start monitoring my rigs vitals. If after monitoring my vitals I decide I need additional cooling, I can always add a heavy duty fan clutch and/or a pusher fan.

Thinking more about the first two points of weakness you pointed out, I agree with you. So I decided to remove the thermostat for now. It’s summertime, and not necessarily required. I also decided to swap the trans cooler for one with NPT fittings, so I can get rid of the failure prone rubber hose and clamps, and run Russell (Edelbrock) ProFlex stainless steel braided hose (Temperature range of -40° F to +350° F, 1000 PSI), and Russell full flow hose ends.

Everything ordered and delivered today, so guess I guess I know what I'll be doing that this weekend. Figure I should probably go ahead and change the transmission fluid, since I'm planning to drive the T to Knoxville, TN the week of July 4th, so I ordered a new filter, gasket, and trans fluid. While I have the pan dropped, I’m going to install the Doorman drain plug, so I can do a drain and fill when I get there, and a drain and fill when I get back.



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Alrock
I was going to use the Derale thermostat #13011 and Long Tru-Cool LPD 4589 trans cooler setup as saftey measure. I don't do any wheeling or have a winch. Just a nice daily driver do you think this is overkill

lc7404 said:

Alrock
I was going to use the Derale thermostat #13011 and Long Tru-Cool LPD 4589 trans cooler setup as saftey measure. I don't do any wheeling or have a winch. Just a nice daily driver do you think this is overkill

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That's the trans cooler I use and I've bypassed the one in the radiator. It's worked well for me so far in the desert heat of AZ. Are you thinking of using it inline with the stock cooler or bypassing? If you are thinking of doing it inline, and you don't tow or go wheeling, I would ask why it would be necessary to add a cooler. You may not have any tangible benefits.

I was going to do it to avoid any possible consequences with the radiator and transmission. Reading on here made me nervous about the potential problems if the radiator went

Cool. Like I said, that cooler has worked well for me and the truck has been well tested.

So bypass correct

lc7404 said:

So bypass correct

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Correct

I was going to do it to avoid any possible consequences with the radiator and transmission. Reading on here made me nervous about the potential problems if the radiator went.

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Ha-ha!! That's the beauty of the internet ...a few people stir a community and others get all scared! (just kidding).

While I don't doubt it 'can' be a problem, and if it happens it could be catastrophic (for the tranny) ...but I haven't seen enough evidence it's rampant. But the belt and suspenders approach can't hurt either! And if yer towing it's a great idea, or live in the hot south. GM probably should have put a cooler on with the Adventure pkg just FOR towing or off-road excursions in high-temp areas like Moab or AZ. They did make a big advertised buzz about rock crawling, didn't they? (rhetorical question).

In the north ya 'need' the heat from the radiator for the other half of the year, I'm going to leave mine as is. But in Tx be aware, as I've stated before, the more you put in front of the radiator, the less A/C heat xfer you're going to get.

Its not a Hummer only problem. My local mechanic told me his brand new land rover radiator broke down internally and mixed oil with coolant leading to his trans to fail. He only got covered for a replacement radiator.
Several members reported it. Its not a common issue but it could happen! I guess the fact that the oem radiators fail and get replaced due to them leaking means not many live enough to fail internally. I replaced 3 radiators due to them leaking but I also wheel so it wasnt a bad upgrade. It sure beats a new tranny and a complete engine coolant flush.
For a cooler environment a tstat is diffenetly needed

Job redone.... this time with Russell braided stainless steel lines and hose ends.



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Awesome!

Mine failed apparently just before month trip to east coast 66k on it
I managed to fix/nurse it to the end but transmission blew ones I hooked up trailer for a weekend trip

Sucky part that I just replaced transmission couple of month ago

I replaced all components related to cooling just because and I think I’ll do bypass too.
Waiting on new transmission from vendor


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Mb30sdl said:

Mine failed apparently just before month trip to east coast 66k on it
I managed to fix/nurse it to the end but transmission blew ones I hooked up trailer for a weekend trip

Sucky part that I just replaced transmission couple of month ago

I replaced all components related to cooling just because and I think I’ll do bypass too.
Waiting on new transmission from vendor


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Damn that sucks, sorry to hear. To clarify, was it the stock radiator/trans cooler that failed you? Or did you have an external trans cooler that failed you?

Original 10 year old radiator.
Not a big deal but still transmission little more expensive vs jk ~1700 vs 1400


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