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Jay D. · 09-14-2020, 11:00 AM

i ask my trans expert he says a max of 285, i think GM also does. he said 290 or so intermittent with a GOOD synthetic oil. the engine normally runs about 200.
Jay D.

randy2828 · 09-16-2020, 11:05 AM

I did mean 225. Last year I towed this trailer for 5000 miles from MI to CA and never have a problem except on those long 6% grades north of Phoenix. The temp gage stays steady as a rock except on these long grades. Should I be able to run at 4000 rpms for 6 to 8 miles without overheating?

bneukam · 09-16-2020, 12:00 PM

Yes, your truck should be able to take that abuse with no overheating issues.
But I would try different scenarios like slowing down, and going into a lower gear, to see where the truck likes to go up at.
I found my trucks sweet spot in long steep grades at 55 mph, at 3,200 rpms.

TB673 · 09-16-2020, 08:12 PM

A good rule of thumb for transmission temps is 100 degrees over ambient temp.
Your truck is working hard pulling these grades.
I towed my 16k trailer to Kansas in late July (ambient temps in the mid 80's) and only hit 160 degrees trans temp twice.
You don't exactly have towing gears, so you may just want to drop 1 gear and bide your time getting to the top of the grade.
If you encounter frequent transmission temps like that, stay on top of the condition of the transmission oil.
Good Luck.

RobbieH · 09-17-2020, 02:35 PM

Quote:

Originally Posted by randy2828

Dry weight of trailer is 5300, My main problem towing up these grades is overheating. My trans temp goes up to 125 and engine temp starts to rise. the air temp was 90. Maybe I just need to replace my radiator.

Does your truck have a tow package with an external (not in the radiator) transmission cooler? If not, all you might need is to install (or have a shop install) a trans cooler. Get the flat steel plate model, the tube aluminum ones are not very durable.

Bowtie Jim · 09-19-2020, 04:39 PM

[QUOTE=Should I be able to run at 4000 rpms for 6 to 8 miles without overheating?[/QUOTE]

You can run it all day long like that. As long as it's getting enough air too keep it cool you'll be fine. You won't pass many gas stations but you'll be fine. These L83 motors are built to rev. I've kept many a 5.3 above 3500 rpm for hours and no problems except 7-8mpg. I've done this on several of my trucks. I've owned 16 Chevy's and never overheated one of them. They don't call me Bowtie Jim for nothing.

6_Riders · 09-19-2020, 07:35 PM

An external, or bigger external, trans cooler will keep your tranny alive for a lot longer then running 225° Temps over the mountains. Not sure what tranny you have, but the 4L60 (probably what you have and the 4L80 (which you don't have), like to run between 160 and 180°. Personally, I'd try to stay under 210 ° and away from anything over 220°.
Have a "tune" made for your truck, for use when towing, won't hurt fuel mileage (probably get better) or longevity of the transmission. This is assuming you have an external trans cooler.

vroom_vroom · 09-19-2020, 08:01 PM

My 6.2 motor heats up to 225-230 on long grades with the max tow/3.73s just put in a bigger aftermarket radiator because of it.....

09 harley · 09-21-2020, 04:23 PM

The difference between a 1/2 and 3/4 is about 13-1500 dollars. The truck has a stronger frame, suspension, brakes. Compare the front suspension and you will see how wimpy the 1/2 ton is. I would love to have one of the small Freightliners to tow my trailer with. You want stout that’s the one. Trade in your old rig and get what you need and like and leave some growing room.