Engine temp

[raptorman53]

The other day I was driving down the interstate pulling my 16 foot trailer with two fourby atv's. I saw it was having a hard time in overdrive so I put it in third. When I did this I saw the temp drop almost instantly. I then went back to OD and the temp came up just as fast as it went down. So my question is why is my truck running cooler at 3700 rpm as opposed to 2600 in OD? Anyway I put a few picks up to describe what I'm talking about. You can look at the mileage to see how fast it change. Thanks for any responses and Happy Holidays.

[Hunner]

My experience with this is that when the torque convertor is locked up but in overdrive with our I5 engines when you lug it on hills or pulling its making the engine work harder. Too tall gearing and not enough power. If you are in 3rd fluid drive or locked the higher rpms are letting it breath better, it has more torque output and circulates coolant more rapidly for better heat exchange. That's my story and Im stickin toit! My Cummins diesel long stroke 6 cylinder does that and it lowers the EGT's by a bunch if Im on long grades. Aluminum melts at somewhere around 1300 degrees I believe! I have a triple lock torque convertor after I blew the stock one and a modified tranny with modifed valve body to do all this. I also added straight cut gears to the over drive. What Im getting at with this is You might want to tow in 3rd if you are having this occur in a Hummer H3.
By the way you are about to run out of gas!

[Malibu1]

and it looks like doing about 80mph, while towing a trailer, and taking pictures of the gauges.

glad I don't live near you.......and glad your still alive

[f5fstop]

Originally Posted by Hunner

My experience with this is that when the torque convertor is locked up but in overdrive with our I5 engines when you lug it on hills or pulling its making the engine work harder. Too tall gearing and not enough power. If you are in 3rd fluid drive or locked the higher rpms are letting it breath better, it has more torque output and circulates coolant more rapidly for better heat exchange. That's my story and Im stickin toit! My Cummins diesel long stroke 6 cylinder does that and it lowers the EGT's by a bunch if Im on long grades. Aluminum melts at somewhere around 1300 degrees I believe! I have a triple lock torque convertor after I blew the stock one and a modified tranny with modifed valve body to do all this. I also added straight cut gears to the over drive. What Im getting at with this is You might want to tow in 3rd if you are having this occur in a Hummer H3.
By the way you are about to run out of gas!

May I add some clarity, it took me a few readings to understand?. At low engine rpm's the friction internal to the torque converter increases heat in the trans and fluid; as rpms increase, the heat reduces. This is due to more circulation, and due to less friction; so a double benefit. Therefore, with the trans in third gear, the rpms are increased, so there is less friction and less heat.

Also, if the speed in third gear exceeds approximately 65-70 mph, the torque converter will lock.

Your fuel mileage will go down....

I believe they do recommend towing in third gear, especially if running in the mountains.

[H3PAC]

Originally Posted by Malibu1

and it looks like doing about 80mph, while towing a trailer, and taking pictures of the gauges.

glad I don't live near you.......and glad your still alive

[raptorman53]

Thanks hunner and f5. That seems to make sence. Thanks for the comments and happy holidays

[whaaaaT]

wahoooooooo is the middle of the gauge hot for everyone else???? cause mine is normally a little above that and im not towing anything.

[whaaaaT]

and hes definatley not even close to running out of gas

[deserth3]

Originally Posted by whaaaaT

wahoooooooo is the middle of the gauge hot for everyone else???? cause mine is normally a little above that and im not towing anything.

Mine normaly runs there or a little above too.

[H3PAC]

Originally Posted by whaaaaT

wahoooooooo is the middle of the gauge hot for everyone else???? cause mine is normally a little above that and im not towing anything.

That's normal. Mine runs right in the middle.