The Dreaded H3 Tranny Cooler / Radiator Issue

[alrock]

No, you'll be putting it behind a 6.2.

 

[3Hummers]

and upgrading the front suspension.

 

[MaxPF]

No, you'll be putting it behind a 6.2.

6.2's use a 6L80 or 6L90 :mock: You can run a 4L80 behind em though - it just wasnt a factory setup AFAIK.

 

[bebe]

I believe Bebe has an external trans cooler, kflips might and TheBroken did as well.

Ron Davis makes a drop in solid aluminum radiator for the H3, but it does have the integrated trans cooler. Hmm, since Bebe runs this she may not have an external trans cooler right now, I'm not sure.

Correct - the only way to gurantee this doesn't happen is to get rid of the GM rad, or put in an external Trans cooler.

IMHO, the external transcooler is a bandaid, it will not cool the tranny as well as the Ron Davis Radiator.

H32NV has one also.

It may seem pricey, but it's the best insurance there is. Pay for the RD Radiator or pay for a new trans and cooling system.

 

[jerseymark]

Does this affect all H3s with auto trans? or did they fix it on later models? Also, how common is this problem?

 

[bebe]

I don't think I can answer that question because I don't know. Hummer wise, I know both H2 and H3 owners who have suffered. But if you Goggle it, you'll see it's an integrated tranny cooler issue Brand wide. The flaw is in GM's design.

I don't think it's super common, but I saw it this way...why leave my self open for a disastrous, expensive failure? It could happen at home, or when I'm out in the middle of nowhere. When it happened to Sewie and Rich, they were without their rigs for a couple of weeks. There is no warning, once it's done, even if you catch it in time, you may not have to replace the trans, but it will need to be rebuilt (all new bands etc,)

The cost can be horrific, a new trans, a new radiator, flush the entire cooling system, replace all the hoses, filters, sensor, thermostat etc etc.

I plan on having my rig for a long time, so $1,000.00 seemed cheap compared that bill (mentioned in the sentence above). And the other benefits...much better cooling for both your engine and your trans mean a longer life for both, and longer periods (not by a ton) between fluid changes.

You could add a "real" trans fluid cooler, but you'd have to find a place to mount it, and plumb it/cool it individually.

That's my thought process anyway.

 

[bebe]

6.2's use a 6L80 or 6L90 :mock: You can run a 4L80 behind em though - it just wasnt a factory setup AFAIK.

I'm pretty sure the 2009 H2 with the 6.2 ran it with the 4L65E.

I'd have to check.

 

[alrock]

I would not say it is common but the problem is that if you have this failure it is a HUGE issue.

Heck, with everyone's radiators cracking it's almost like a safety device that this type of failure doesn't have a chance to occur :roll:

 

[MaxPF]

I'm pretty sure the 2009 H2 with the 6.2 ran it with the 4L65E.

I'd have to check.

You're probably correct. I think the 6L's were first used in the Caddy's and phased into the trucks around the time the H2 was slated to be phased out. There's also several different RPOs of 6.0's and 6.2's, and the trans each engine was mated with was year and platform specific. Makes it good for swappers

Now that Jerry S's wife has her own ride, Jerry was talking about a 6.2 swap too :giggle:

 

[jerseymark]

Correct - the only way to gurantee this doesn't happen is to get rid of the GM rad, or put in an external Trans cooler.

IMHO, the external transcooler is a bandaid, it will not cool the tranny as well as the Ron Davis Radiator.

Why is it only a bandaid? Is there a big downside to doing the external cooler instead of the RD radiator? $1000 is a little steep for the radiator and a trans cooler is a lot less. Plus it seems like it would keep the tranny cooler than the built in one on radiator.

Part of the reason I ask, is that I have a trans cooler that I was going to install on my wife's jeep wrangler(2011, these have been know to have auto trans temp issues and have no factory cooler). I planned to do this when her bumper to bumper warranty ends in a few thousand miles but she is having some oil consumption issues and may end up trading it in. The trans cooler is a factory mopar accessory kit so it is made for the jeep but I think if I just used to cooler without the brackets I could get it to work on the H3. The jeep does use different trans fluid(ATF+4) I think but I didn't think it would matter for the cooler.

 

[bebe]

Why is it only a bandaid? Is there a big downside to doing the external cooler instead of the RD radiator? $1000 is a little steep for the radiator and a trans cooler is a lot less. Plus it seems like it would keep the tranny cooler than the built in one on radiator.

Bandaid...well because it doesn't cool as efficiently, unless you get a BIG cooler. F5 brought this up a long time ago when I first put on my external cooler. These trannys are designed to run the same temp as the motor, the integrated cooler in the rad cools the trans to be within 10 degrees of the water temp. The flexalite is ok, but not as good, because of the electric fan.

We've had the discussion about how electric fans can't cool as well as a clutch fan. That said, you would need a BIG external and a really big fan to be able to accomplish what the clutch fan can.

This whole conversation doesn't even mention Ram air (air flow from speed) like going down the highway.

Here is the way a "real" external cooler looks - they also call them heat exchangers and have many applications, as well as transmission cooling:

And this is how they are plumbed:

Don't pay too much attention to the shape of the external in the drawing, there can be many shapes.

Now, how do you know when your transmission is not being cooled properly?

When you check the oil it's dark, meaning cooked. It gets cooked when it's running at high temps for extended periods of time. Towing, carrying heavy loads (ie lots of mods like roof racks, winches, heavy bumpers etc...) Extended time in traffic. All of these things add load and reduce Ram air.

Most of you will notice in traffic when your clutch fan engages, this is the roaring sound you hear sometimes going up hills, when you are in traffic etc. It usually only last a minute or two depending on the situation.

When the clutch fan engages, it increases the fan speed behind your radiator, sucking Ram air through at a higher speed to cool the engine and trans.

Another discussion to have is corrosion. That little reservoir in the bottom of your radiator is connected to it, so that the water in the radiator cools the liquid in the reservoir as it passes through. The GM rad is made out of a material that corrodes quickly with rust and sediments, unfortunately, and a lot of that has to do with the liquid you put in your radiator.

Edited to add another visual - our radiator looks similar to the one on the left in this drawing:

Now that I have the Ron Davis, I have to use a 50/50 mix still, but is has to be mixed with distilled water, which I personally think everyone should use anyway, even with a stock radiator. It again is a little more insurance that your not adding corrosives to the rad. With the all aluminum radiator, it has fewer chances of being corroded, because it doesn't rust.

Brodie made a video on how to clean your radiator, and I'm sad to say I bet a lot of folks don't do this maintenance as often as they should. And to add that flushing the cooling system will prevent sediment from building up in the bottom the radiator, and corroding the reservoir with the trans fluid.

I hope this helps

 

[bebe]

This past Friday, Cotilo's '08 H3 Lux rig had the the tranny cooler inside the radiator give out. If/when this happens, you will get anti-freeze in your tranny and the tranny will be fried real fast. If the repair is not covered by warranty (B & B or the GM extended premier plan) you are looking at a new radiator, hoses, seals, gaskets & transmission needing to be replaced at an estimated cost of $2,000-4,500 - and possibly needing a new engine if the antifreeze got sucked into the engine and damaged the engine. She had it towed from her work to the GM dealer/HUMMER service facility

When the milkshake happens, it runs all through your block, and water pump. Not likely that you will need to replace the motor, but everything will need to be flushed, filled, cycled, burped, flushed, filled, cycled, burped until everything runs clear. You can probably add a few hours of labor for that process alone. Like 10. Anything that that mixture touches, is toast. (meaning seals, sensors thermostat etc.).

The only reason they would replace the motor is if it over heated and warped the head, or if it's just easier than having to strip it down and throw it in a hot tank. That oil will now line all of the cooling passages in the block, which without proper cleaning, will never be right.

 

[jerseymark]

Bebe,
Thanks for the info. I see what you are saying and ideally I would want the oil cooler to run through the radiator(and ideally the all aluminum one) and then an auxillary cooler. For now I am going to just flush the radiator regularly. I still have 1 year on the bumper to bumper warranty and 2 on the powertrain and I don't want to change anything that could void the warranty. I may get the aluminum radiator after warranty is up, but I wish it was less expensive.

 

[MaxPF]

Bandaid...well because it doesn't cool as efficiently, unless you get a BIG cooler. F5 brought this up a long time ago when I first put on my external cooler. These trannys are designed to run the same temp as the motor, the integrated cooler in the rad cools the trans to be within 10 degrees of the water temp. The flexalite is ok, but not as good, because of the electric fan.

We've had the discussion about how electric fans can't cool as well as a clutch fan. That said, you would need a BIG external and a really big fan to be able to accomplish what the clutch fan can.

This whole conversation doesn't even mention Ram air (air flow from speed) like going down the highway.

Here is the way a "real" external cooler looks - they also call them heat exchangers and have many applications, as well as transmission cooling:

Sorry to disagree with you Bebe, but those types of coolers have very poor efficiency. By far and away the most efficient are the high density plate and fin style. Setrab makes the best ones:

Todd runs a similar cooler on his Jeep with no in-radiator loop. Normal trans temps are 140-150, while the highest seen has been around 200 (towing a pop-up camper up the mountain with the throttle hammered). This is with a 6.0 and 4L80E. These coolers definitely get the job done.

FWIW, the reason he no longer loops through the in-radiator cooler is because he no longer has one. His original Ron Davis radiator had an in-tank trans cooler, but when it developed a leak (only 2 years old!!!) he replaced it with another manufacturer's radiator, which is a double-pass design. Because of that design there is no room for an in-tank exchanger, so he was forced to use the external cooler alone. It hasn't been an issue.

 

[JonBishop]

if we were to purchase one of those coolers which one is it?... i was lookin at the list an have no clue what im looking for lol

 

[bebe]

Sorry to disagree with you Bebe, but those types of coolers have very poor efficiency. By far and away the most efficient are the high density plate and fin style. Setrab makes the best ones:

Don't apologize, it was just an example of a finned cooler - the only pic I could find in a quick google search while on the phone with a customer. I wanted to show them the difference between the flexalite and an exchanger.

 

[MaxPF]

if we were to purchase one of those coolers which one is it?... i was lookin at the list an have no clue what im looking for lol

I have no idea - I've never installed a cooler on an H3. You need to figure out how large of a cooler you can fit in front of the existing cooling stack. Things like the center support can be an issue. You want to fit the largest cooler possible, particularly if you are bypassing the in-rad cooler.

I should mention that an external cooler can cause an issue in cold weather, especially if the in-rad exchanger is bypasses/deleted. The trans may never get warm (at least 140, preferably 160 degrees). If that happens, you need to partially or completely cover the cooler to allow the fluid to warm up. The PCM/TCM is programmed to not lock the converter at all when the fluid is cold, so that helps it warm up as well.

 

[chaos254]

You can always run a thermostat if you are in a colder climate. It will bypass the cooler until temps reach ~170. After that it will route fluid through the cooler

Sent from my cm_tenderloin using Tapatalk 2

 

[3Hummers]

Bandaid...well because it doesn't cool as efficiently, unless you get a BIG cooler. F5 brought this up a long time ago when I first put on my external cooler. These trannys are designed to run the same temp as the motor, the integrated cooler in the rad cools the trans to be within 10 degrees of the water temp. The flexalite is ok, but not as good, because of the electric fan.

We've had the discussion about how electric fans can't cool as well as a clutch fan. That said, you would need a BIG external and a really big fan to be able to accomplish what the clutch fan can.

This whole conversation doesn't even mention Ram air (air flow from speed) like going down the highway.

Here is the way a "real" external cooler looks - they also call them heat exchangers and have many applications, as well as transmission cooling:

And this is how they are plumbed:

Don't pay too much attention to the shape of the external in the drawing, there can be many shapes.

Now, how do you know when your transmission is not being cooled properly?

When you check the oil it's dark, meaning cooked. It gets cooked when it's running at high temps for extended periods of time. Towing, carrying heavy loads (ie lots of mods like roof racks, winches, heavy bumpers etc...) Extended time in traffic. All of these things add load and reduce Ram air.

Most of you will notice in traffic when your clutch fan engages, this is the roaring sound you hear sometimes going up hills, when you are in traffic etc. It usually only last a minute or two depending on the situation.

When the clutch fan engages, it increases the fan speed behind your radiator, sucking Ram air through at a higher speed to cool the engine and trans.

Another discussion to have is corrosion. That little reservoir in the bottom of your radiator is connected to it, so that the water in the radiator cools the liquid in the reservoir as it passes through. The GM rad is made out of a material that corrodes quickly with rust and sediments, unfortunately, and a lot of that has to do with the liquid you put in your radiator.

Edited to add another visual - our radiator looks similar to the one on the left in this drawing:

Now that I have the Ron Davis, I have to use a 50/50 mix still, but is has to be mixed with distilled water, which I personally think everyone should use anyway, even with a stock radiator. It again is a little more insurance that your not adding corrosives to the rad. With the all aluminum radiator, it has fewer chances of being corroded, because it doesn't rust.

Brodie made a video on how to clean your radiator, and I'm sad to say I bet a lot of folks don't do this maintenance as often as they should. And to add that flushing the cooling system will prevent sediment from building up in the bottom the radiator, and corroding the reservoir with the trans fluid.

I hope this helps

Damn, smart women are so sexy.

 

[bebe]

:giggle:

 

[WarMongur]

Add me to the list of the SCREWED!!!! and with only 37,876 miles ..... CRAP!

 

[Chook]

What external cooler is everyone running? Anyone have a write up for doing this? After reading this I want to get this done soon because I definitely can't afford that kind of issue Sent from my cm_tenderloin using Tapatalk 2

I put in a Derale 13900 (probably the largest one that will fit the H3 I5)

I put all the details here @ post # 19 (let me know if you need more info)

http://www.hummer4x4offroad.com/forum/showthread.php?2554-Transmission-Temp/page2&highlight=cooler

 

[alrock]

WarMongur, are you under warranty?

 

[Zach]

WarMongur, are you under warranty?

Unfortunately, he's out by time

 

[R-code17815]

Mine cracked yesterday...:whaa:

I used some DEVCON Plastic Welder and patched it up till I can get to the bank Monday.:roll:

I did some research & found a universal Alum. Rad. almost the same size, with inlet/outlet on the proper sides.:thumbs:

I'm going to just make my own mounts & get a separate Trans cooler.:thumbs:





Any size recommendation for a stand alone Trans cooler?:huh:

Would 18,000 gvw be enough?:cheers: