Could be a bunch of stuff.... Not much info...

Radiator clogged from YEARS of bugs and dirt?
Thermostat?
Hoses? Are they collapsing?
Pump?
Coolant Level?
Coolant Condition?
Tranny Issue?
Truck running hot form overload?
Truck running hot from modification?
Is it really hot?

 

And for reference Cummins states that 180-215 is acceptable operating temp range.

 

This is why I'm suspecting the GV is contributing. Assuming everything checks out, i.e. no actual mechanical malfunction, I'll bet if he stays in 3rd direct with the rpm up around at least 2500 his problem will be greatly reduced, if not go away entirely with the relatively small load he is pulling. Everything slows down, including the cooling effect with lower rpm - higher EGT + fluid/coolant circulating slower + more Tq converter slip = too much heat to dissipate effectively with whatever the installed coolers happen to be.

 

When I pulled with 4.10s and steep grades, IF I could keep it at 45mph in 3rd, all was well.
Once it went below that, say having to slow and go around a truck, then try to speed back up, it usually ended up with me cooling it down on the side of the road a 1/2 mile later.

The 3.54s in my 2nd gen (with a VE engine) were actually worse, it ALWAYS ended up needing cooled off.

RPM when pulling heavy in the hills is definitely the key, but there's a sweet spot on air flow and RPM and you BETTER have a good clutch fan doing it, or you'll both triple the roadside time AND kill an engine.

Those high hills out West will absolutely test your truck's brakes and cooling system.

"Chug-A-Lug-A-Luggin' up one side, backsliding down the other, I'm a lover of the other side of the hill....."

Mark.

 

A hole On my 1st gen factory setup there is (Not 2 or 3) but ONLY 1 trans oil cooler that is sharing the coolant system (the one on the side of the engine) The 2nd is in front of the radiator all by itself. so kiss it.

LIke Mark Nixon said "Used to pull a 40 foot 2-car trailer with 2 fullsize Chryslers through Colorado and it would overheat every time.
I changed radiators, cooler thermostats, hotter thermostats, new clutches, heavier fan clutches, you name it, I tried it. Numerous times.
It was an untouched 1stgen with a 5 speed with 4.10 gears."

So looks like it is back to what I first said about the cooling system not being SUFFICIENT enough. I'm not saying an auto isn't hotter I know they are HOTTER

 

J, To add insult to injury, the ones I had were MANUAL TRANSMISSIONS.

Mark.

 

I believe he has a radiator issue and possibly turned up pump issues. I have had 2 1st gens, first was non I/C and my 92 i/c, both had getrags. They both ran in the normal range before i cranked up the pumps. I would see 1300 post turbo egt's on my non i/c but never had a melt down. Both rigs will get hot on temp gauge when i haul scrap up our hill, 3,000 lbs trailer and 6 to 7k of iron. If i stay in 4th gear in getrag i can hold about 1100 on the pyro on my 92 with 3.54 gears. And that is to the floor! The non i/c truck would get noticably hotter on pyro but never would overheat. So that leads me to believe he is getting to much fuel and not enough air thus leading to higher egts than he is seeing and causing coolant temps to rise.

 

Ok so I do not think my pump is turned up but not 100% sure I would know how to check that. I have an automatic that is cooling directly into the radiator. The radiator is a 4 core that seems be clean and has been rodded at some point. When I pull the same hill with my 5th wheel I didn't notice the over hearting but pull it with the big trailer the temp rises.

Suggestions from Radiator shop is to go with a more "Severe Type" fan clutch. I still don't know what size trans is in the truck or what the RE Gears are ohwever I did kick off the GV to make sure I was pulling enough RPM and still seemed like it was climbing. So now what?

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Would a secondary trans-cooler be helpful? That way I can get more cooling on those lines. Thanks

 

Well i agree with the fan clutch, one that stays engaged longer would help on a long pull. A picture of the pump and and a concise explantion would easily tell you about your pump. Hopefully someone will chime in with a pic.

 

It really shouldnt matter because when it past a certin temp it stays ingaged until it cools back down.