This is something that is bothering me too.
I have the stock fan
I have a 180 F Tstat
I found the underdrive pulley did make a difference.
On the highway at 70 to 75 mph - temp sits at 185 but
as soon as I stop or hit traffic - stop and go
it will sit right on 210 and will only move once it gets some air flow
Trans temps - dont know - dont have my trans temp gauge hooked up
yet
I do have the trans cooler inline with the radiator cooler
I have been thinking about replacing the stock rad with the 6.0 rad and
a 160 F Tstat
The cooling system seems very touchy and unable to cool the motor
consistently.
Any thoughts - Daniel you thinking along the same lines

 

for ECT.
the thermo as you put it is a temp pressuer value.
the higher the temp the more the value is open by the pressure created inside the value.
on a 180 the value will start to open at 168 / 170 it will be barley cracked open as the temp rises to 174 / 175 the value will be open about 1/3 and at 180 the value will be open at 3/4 when you hit the 182 or 183 mark it wil be open all the way allowing the water to flow at full speed.

as the value slowly opens it lets the water pass through the radiator slowly allowing the air to cool it fast, as it opens more the flow increases making the water spend less time in the radiator to cool, at wide open the flow is fast and the only thing cooling is what little radiator you have. if it is not enough get ready for cracked heads down the road.

to make the motor run cooler you need a bigger radiator with a bigger radiator you can run at a lower temp,

i'm running at 140 with a tripple core at 70 mph all the time, i have made a 20 mile run at 100 and it never moved off of 140 at any time.

 

Got my 6.0 radiator from Radiator Barn for under $300 shipped.

 

your theory makes since, but I dont think it's what is happening here.
If that was the case the temps would never come down because of the water not slowing enough to cool, but yet if I get on the highway, the temp will come down to about 3 lines below the 210 mark on the motor and the trans will run around 150 to 160. but like Chris said as soon as I hit the streets up comes the temp, and it wont come back down. Now correct me if Im wrong but wouldnt the water pump slow down the velocity of flow if at or near idle?
but be faster on the freeway, therefor the coolant would move slower through the radiator while sitting than it would driving., but yet the truck gets warmer, sitting.
Now mind you I said it's getting warmer, not over heating. It hasn't got above 210*, but I am wanting to catch it before it gets that far.
thanks for the imput guys, I just dont wont to get stranded with the days getting hotter here in Houston

 

thanks Greg I will look into that

 

the water pump is that just a pump to push water.
now to make pressure the room between the pump blade and the houseing wall must be small the less room the higher the pressure the more room the less pressure, i know it is hard to under stand but if you work with pumps like i do then you know what i am talking about. there is a big deffrence between a pump that can make 90 psi and one that can make 50psi it is all on the inside even though both pumps look the same.
our water pumps can make pressure but not that much at 90 psi the clamps wil not hold and the tanks wil blow off even the radiator cap has a max psi of 12 to 18 depends on what you have.
at 4000 rpm's our water pumps are trying to push water through the radiator core will be no more then 5 psi max, as much as 8psi if you have an aftermarket brand name pump add on to that prussure made by the heatting of the water in our motors. at normal the system has an operating pressure of 9psi to 10 psi on the hoses, clamps, tanks, and the cap.
our water pumps have room for the water to roll in side them for when the temp is low and the stat is closed if we did not have this room and the pumps made 90 psi we would need copper or steal gaskets on the heads and a much stronger hose, clamps, and radiator for when the stat opened it would blow everything apart, now were talking big bucks for replacement.
now the cap has a releaf psi of 12 to 18 this is a safety messure to keep from blowing everything apart for when the motor overheats and the water is just boiling in side the block, it was also put in to keep from being swamped in hot water and steam should the hose blow when you pop the hood.
the motor companys don't like law suits for makeing a dangerous product

if you live out in the same area as i do around houston when was the last time you cleaned out the AC core and the Radiator core from all the bugs we have so air will pass through?
and if you are useing water out of the hose you mit have a mineral build up on the core, get the radiator rodded out, this will make it like new, most shops can do this in 2 hours and under 100.00 bucks.

want to see what i am talking about on the stat, drop one in a pot of water add heat, as the water temp gets higher you will see it open slowly.
water bolis at 100 degrees cle. and at 210 fer, and at over 300 kel.
you can use a torch but the seals on the stat will be fried
for every pound of pressure on your cap will up the boiling point on your system by one degree.

 

i believe that they were wondering if you were using the temp gauge for the engine temp. my gauge will read at the same mark that the factory temp was and with a predator i will see 182°.

 

The factory gauge is def off - as soon as the truck gets warms it will sit at 210 no matter what - reason I added an Autometer gauge with the sender in the RR head.
I am in Daniels camp
I would like for mine to be more consistent in keeping the temps in check without a wide temp swing.
I checked the Radiator Barn as Greg did - that is what I am going to do first.

Pappy 140 F ?? - little too cool - and many reasons an engine should be at 160 F

Dont feel pumps are the issue - I feel the issue is an ineffective radiator/ cooling system which is unable to keep temps at a consistent level.
Reason I will start with a 34in 6L rad first.
I feel the truck should be able to run in stop and go at a reasonable level without going from 185 to 210 within 1 minute sitting at a light.
Should it creep up - yep - but mine will hammer 210 as soon as I sit for what I feel is a short time.
I know it is not a cleaning issue - I have 6,200 miles
I dont have this issue with my other 7 veh's.

 

The stock pumps are capable of flowing 80gph? or something like that. They are not the problem.

I used to have a S10 with a 355 SBC in it. Do to clearance problems I had to run electric fans. I couldn't get very deep ones cause there just wasn't room for them. I put them on a stock radiator and had nothing but cooling problems in traffic..BAD cooling problems. I put a bigger 2 core radiator in and that helped but, the fans just couldn't pull enough air to cool things off.

That is why I went with the biggest radiator(direct fit) and highest flowing fans(direct fit) that were available. The LS1 fans work but, I really don't think can compare to the flexalites. The extra size of the 6.0L radiator helps also. GM just didn't put it in there for no reason. They test the crap outta that stuff to make sure they don't get a bunch of overheated blown motors back under warranty.

We may not have 6.0L's but, when you start modding the 5.3L it will put out similiar power even with simple mods.

My recommendation based on the only thing I have tried is a 6.0L radiator, 282 fans, 160 thermo. I KNOW that works with the A/C blasting, sitting in stop in go traffic in the middle of 4 lanes of cars, on the hot blacktop, for hours in 95+° heat.

I was paranoid when I first put the fans in but, not now.

 

I am having the same issues with my 6.0... The thing just stays at close to 210, ith a 160 stat... I have given up, I am thinking about putting on the stock stat with the BB mod, or poiling the 160 to makle syure it is working corectly... ohh well, I guess some trucks are just built differently from others...