I got a super cooler also. Works great, bumper off, or on.
At 60 that sucker should have more than enough air going through it.
It's my understanding the force of air takes over from the fan around 30 mph.

I'm thinking cavitation or nucleic boiling. I wonder if there is an cheap, easy way to measure differential pressure across the WP on the fly?

Glad you liked the link, that guy is sharp who wrote it.

GL

 

When the RPMs increase rapidly it may be an indicator that the transmission is slipping or that drag is increasing rapidly causing the transmission torque converter to slip more. Either will cause the temperature to climb. Brakes or wheel bearings binding can cause loads to increase. Putting the transmission in Neutral at speed (carefully) can help detect drivetrain drag. If the vehicle slows rapidly it can be due to drag.

 

I took my bumper off yesterday and took her out for a drive. The outside temp was about 92, so it took a little longer to heat up. It still overheats, but when I got home I started taking temps with the infrared thermometer thingy. When I did that I noticed transmission oil coming out of the bellhousing. Fortunately I had a drip pad under it, I took a temperature reading of the tranny pan and it was at 220! And so was the top radiator hose, the top and bottom of the radiator, and the bottom hose!!!!!
Sooooo, I'm thinking that when I changed the old 2.75 rear end and stock tires to the 3.55 and 32's I changed the top end rpm too much, and started heating up the tranny only on the freeway, so the radiator cant handle the heat.
Today I went out and got an auxilary tranny cooler, and just finished installing it. Outside temp right now is about 78 so I have to wait until tomorrow to test it.
Oh I almost forgot, the oil stopped coming out as soon as I started runing water through the radiator. I drove it to work today and it didn't leak anymore.
I've got some 3.08 gears for the diff. I'm thinking of putting those in to lower my top end rpm a little. Although, I do like the take off speed that the 3.55 gives me.
I'll keep all of you posted,
Firefdude

 

Using the formula below, your rpm range at 65 mph is right about where it should be.

(MPH X Gear Ratio / Tire Diameter) X 336 = RPM. Acceptable RPM range is 2000 - 3000, with optimum being 2300 - 2600.

Using your numbers, (65 X 3.55 / 32) x 336 = 2423 rpm, which is right where it should be. With 3.08 gears, the rpm at 65 mph would be 2102 which is in the range, but on the low side. At 55 mph the 3.08 gears would run 1778 rpm, which is too low.

The calculation is courtesy of Bronco Graveyard catalog.

 

I wouldn't run a 192 deg thermostat in 90 deg heat. Try a 160 high flow.

 

Where is your fan mounted in relation to the shroud? The fan should be mounted about an inch inside the shroud.

What diameter is the fan? As original, it should be 18-18 1/2 inches in diameter without Air Conditioning. 19 1/2" with Air Conditioning.

How many fan blades? As original either 5 or 7 blades were offered. With A/C, the viscous drive (fan clutch) was standard equipment.


The original thermostat installed in these trucks when new was 192 degrees. Many were changed to either 160 or 180 degrees by Ford dealers in hot climates, after customers complained about their engines running hot.

D7TZ-8146-A .. Fan Shroud - Use with Extra Cooling or A/C Radiators / 351M/400.

This shroud is STILL AVAILABLE FROM FORD. List price: $132.22.

 

[QUOTE=NumberDummy]The original thermostat installed in these trucks when new was 192 degrees. Many were changed to either 160 or 180 degrees by Ford dealers in hot climates, after customers complained about their engines running hot.QUOTE]

ND, do you have a PN for a 160 Tstat? i wasn't aware of any but the 192* and 180*

the thermostat only sets the LOW limit for the running temp, the engine will still continue to run at it's own HIGH temp regardless of what the Tstat value is. the radiator and airflow through it determine how much heat the cooling system is able to remove.

 

Here's a pic of my custom fan shroud, the fan is a seven blade and I have a thermal fan clutch. But like I said before, the overheating does not occur until I get on the highway and the ambient temp is above 95. I'm also thinking of rounding out the edges of the shroud to get more of an aerodynamic flow of air instead of the box type that you see in the picture.
I did drive the truck on the freeway yesterday and the temp only went up to about 190 on the tranny, so the coolant temp stayed at about the same. But the outside temp was only 85.

 

Do you know how far the rebuild went when overboring? I'm leaning towards Danlee with this one and friction and thin cast walls that may have been bored too far.

 

I just went to http://www.csgnetwork.com/multirpmcalc.html and these are my findings.
original set up 2.75 gears/ 28.87 tire diam/ 65mph= 2136 rpm
now 3.55 gears/ 32 tire diam / 65 mph= 2488 rpm
with gears 3.08 gears/ 32 tire diam / 65 mph= 2158 rpm
So I think I'm going with the 3.08 gears. What do you all think?

 

At highway speeds there will be enough air flow that you don't need a fan, even at 95 degrees ambient air temp.

So your problem is not air flow, if it will stay cool at idle and low RPM.

It could be a colapsing bottom hose, slipping belts, or excessive load for the capacity of the cooling system.

Does the problem occur only when you are running uphill?
Does it tend to cool off running downhill or level?

If so, then it is a load/capacity related problem.

If it occurs regardless of the load, then it is a RPM or speed problem.
This could be a glazed/slipping belt, or colapsing bottom hose, or a drive train friction problem.

The friction can be in the motor or a bearing as Eric mentioned.

Does it roll easily when in neutral with the brakes released?
Feel the wheel hubs after driving for a while. Are they hot?

 

Well, the truck still overheats. But the other day I was rechecking my timing and when i was trying to get it to tdc, I was bumping the engine with the starter. and I would hear air coming from the engine. I really don't know where its coming from but it would happen every time I bumped it. IS THIS NORMAL??????

 

1. it seems like the fan is a non issue...ie like others have said the design of the fan is to allow the air at 60mph to cool which is when it is overheating... nix fan.

2. rear end ??? don't like that as the problem either. running lean could attribute...

but the # one answer thus far IMHO is the friction by danlee and matts72.

I have a wheezer i built doing the same and i'm pretty sure thats the issue...problem is it sucks to have to fix it. I knew I had a main bearing that was too tight (could be a squish problem) and should have fixed it before install. arrrrgh. it initially wouldn't start once hot and it still runs hot when the rpms are up.

Look at it this way...the heat is an energy that is stored...you increase the rpm and, thus, friction and the cooling can't compensate very well...the heat stores more energy...then you slow or quit and the cooling capacity decreases and is unable to handle the heat that is stored. Main bearings expand and you have a brake on the crank....one scenario.

so maybe it will be ok if your cooling capacity is increased by parts or effeciency of cleaning it out and all is good...or survivable.

or you are about to have an engine issue.

 

Not unless you have a missing or loose spark plug.

Is the motor quiet when running?

Is your exhaust plugged?

 

the motor is pretty quiet, I get about 14 vacume at idle, except for the overheating problem that I havent been able to solve . I have true dual exhaust thats about a year and a half old with turbo mufflers. I'm gonna investigate further and see if I can isolate where the air is coming from.