Towing well under max but rising temp

[bendyprissy]

So we went camping to Possum Kingdom Lake State Park, great place by the way. Used the 2006 h3 w/ adventure pkg to tow a 2500 lb pop-up camper that was 14 ft long.

Most of the trip was flat or small hills. 3/4 of the way we got into the hill country where the hills get bigger & much more frequent. That's where the temp started to rise a slight bit over normal temp but stayed ok.

Then the last 30 minutes of the trip we got into the beginnings of the Palo Pinto mountain range. These were small mountains as far as most mountains go; however , the hummer started struggling. It would kick into a massive overdrive & the temp rose to just under the 3/4 mark. If it had rose any higher we were going to turn on the heater...in the middle of Texas summer. Luckily that didn't have to happen.

We had to pull over to restrap the kayak & saw there was plenty of coolant in the overflow tank so it wasn't leaking. We were thinking possibly stuck thermostat or water pump.

Anyone else have this issue? What are your thoughts ?

 

[zackcrum]

Can't help you but I will comment on that over drive issue. Since the day I got my three it has done that and it scares the **** out of me! Like it revs all the way to 6k before shifting and i hate it. So I don't use the cruise control anymore and rarely take it over 60 mph

 

[f5moab]

The H3 is not a tow friendly vehicle. Temps will rise, and if you were watching your trans temps you would be shocked. If you intend to do any towing with the H3 I highly suggest a stacked plate trans cooler be installed, and use only synthetic oil since your oil temps go up considerably when pulling a load up a hill.
When towing towing through the rockies from Denver, the trans temps went up to around 220...not good, but not a killer for short periods (however, over the long run it will require a trans fluid change/flush more often). I had the dealer install a B&M stacked plate cooler and the temps never went above 201 from then on.
A month or two later, pulling the trailer through the San Rafael swell from Zion to Moab, the oil temps hit around 260-265 and I believe (not sure on temp) the engine will go into reduced power around 280 degrees.

The H3 at high speeds (above 50 mph) is not a tow friendly vehicle with the I5 engine. With the 4.56 gearing, the small engine, and a load it just keeps that engine at a high RPM. Especially when climbing an incline.

 

[3Hummers]

Our H3 routinely runs with the temp guage at the 2/3 mark and on hot days it will hit the 3/4 mark not even towing. The Alpha could use a better cooling set up for sure.

 

[Best4x4]

I know the trans temp needs to be as cool as possible, but 220F is nothing. I've owned a lot of 4x4 rigs, and the normal ScanGauge II temps on all of them averaged around 210-240F. My Hummer's run basically the same Trans/Engine temps minus a few degree's. Your temps sound completely normal to me especially when towing and in extreme TX heat.

 

[f5moab]

NO 220 degrees is something, it will limit the life of the fluid. Does it mean that 220 will destroy the fluid and the trans...NO. But overall, any increase in temps above about 190 will cause the fluid to degrade faster. So instead of 100K, it is now down to 50K (just an example).

Newer fluids such as Dex VI or some synthetic fluids will take higher temps over a period of time better than older fluids. The three biggest killers of any powertrain components are:
Low fluid (which in turn causes the fluid to heat up since fluids such as trans and engine are also used for cooling)
Fluid exceeding the recommended heat spec
And incorrect fluid.


This chart is very outdated when compared to modern fluids, however, the theory is the same, even if the temps and miles are extended....

If high temps on trans fluid was not a problem, then why do manufacturers install coolers to cool the fluid, and install auxiliary coolers on vehicles with tow packages? And let's not forget that the maintenance schedule may require a fluid to be changed more often under certain conditions and most of these conditions are determined by the heat generated for that type of operation such as mountain driving, idling for a long period of time, stop and go traffic, pulling a trailer, etc.

So, even though running at 220 or even 240 will not IMMEDIATELY kill the fluid, running at those temps will decrease the life of the fluids. So change more often, or find someway to keep the temps down into the "normal" operating range. Thus an external cooler on a H3 is a great investment if you are pulling a trailer in the summer.


As for the engine temps, I can honestly say that when the Alpha was released some of us on the H3 project were a little bit worried about the cooling capacity of the Alpha system. Turned out it was not as bad as some of us thought, but to this day, I believe the Alpha has an undersized cooling system.

 

[K0PIR]

I have an 06 lux, auto trans. and I tow a pop-up too and in the summer heat 220 isn't a concern for me. Mine goes to 3/4 mark and handles it fine. It will even go higher and then I just slow down a bit. 65 to 70mph is about as fast as I go towing. 60 is best. 45mph up hill is common too. I drop it to 3rd and go slow when towing a real heavy trailer and it does fine. No constant shifting or high rpm's. Easy does it!

 

[SedonaBound]

Even with no tow, the I5 struggles to hold highway speeds on mild grades. The power-to-weight ration of the I5 is about 20lb/hp, which essentially puts it in the econo-box power class. I think a 2500 lb trailer is pushing your luck. Towing rating criteria isn't a govt standard, and pre-2011 when SAE put out a standard, was pretty much what ever the mfrs thought they could get away with. What the H3s really needed was a 6-spd trans to stay on the power curve.

 

[Best4x4]

I have two H3's. One is modified, and one is fairly stock 220F has been reached in traffic, or the extreme TX heat, if 220F is so extreme/horrible I'm sure Hummer/GM would have fitted a much larger transmission cooler from the factory. I stuck one on my wife's H3 and it took forever for the transmission to warm up. Until then OD didn't engage and it was like 6 miles.. Drove like crap without OD..

My FX4 ran 230F trans temps, never had an issue and I towed like a madman with it.

I don't listen to dealer 100K crap. I do drain/filter changes at 30k.

 

[kilroy]

Excessive heat is and always will be the enemy of even the best built automatic transmission and 220F is getting close to pushing the edge. That being said, the best things you could do would be to install an external trans cooler, and since it sounds like you were towing in overdrive do NOT tow in OD. Unless the vehicle has towpower (06 models didn't have this) it is not meant to be used to tow in OD and don't expect to run 70+ while towing. I myself have a 2000lb Jayco pop-up and drive through long moderate grades (2 to 3 mile long 10+deg), stay out of od and do not exceed 60mph and all runs great.

 

[USMC_TOP]

MashMotors seems to have a fix for all our H3 lacks........ I have towed 2 vehicles on car dollies with my 3 without incident as far as temp but you sure know your towing something. With today's vehicle prices I think a 6.2 matched with a 6 speed trans would make a hell of a 3. And it's a cheep upgrade compared to a new Yukon.


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[bendyprissy]

Thanks y'all. Will post some pics over in expeditions or one of those threads over there.

 

[digglesworth]

I have two H3's. One is modified, and one is fairly stock 220F has been reached in traffic, or the extreme TX heat, if 220F is so extreme/horrible I'm sure Hummer/GM would have fitted a much larger transmission cooler from the factory. I stuck one on my wife's H3 and it took forever for the transmission to warm up. Until then OD didn't engage and it was like 6 miles.. Drove like crap without OD..

My FX4 ran 230F trans temps, never had an issue and I towed like a madman with it.

I don't listen to dealer 100K crap. I do drain/filter changes at 30k.

Did you try running a thermal bypass? Let's the fluid warm up before opening the loop to the cooler. I have issues when it's below freezing having to wait a few miles for it to get above a certain temp and shift into OD. Nature of the beast I guess... But I've never really gone over 210 or so on trans temp with my external cooler/thermal bypass setup. I may double up the cooler just for a little extra.

 

[Best4x4]

Didn't have that installed. Just OEM cooler with aux cooler inline.

 

[jphh20]

I installed the thermal bypass with my bypass trans cooler. Bought the entire setup from derale and has served me very well. The bypass opens up at 179*F and it holds steady unless I'm pushing the capability of the installed cooler. Overall much better than the stock setup and eliminated the coolant mixing concerns as well.


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