TL;DR
Excursuin tranny overheated, Motorhome didn't. X transmission overflowed onto exhaust, lots of smoke. Lost a quart. Looking for advice on how best to control transmission temps. Is burned tranny fluid okay to use?

Details:
We went from Banning, Ca 2000ft to Pine Cove, Ca 7000ft in 23 miles. My wife's father drove the X with the 7,500lb trailer (total 15k?) while I drove the Ford F53 Class A about 28k. We both have the same engine (and transmission as far as I know).

I kept it in drive and he used 2nd all the way up. I have a tuner from 5 Star and pulled over and put it in park when I hit 230° on the transmission. When we checked into the campground I kept it in park idling and he shut the Excursion off. I know we lose HP and liquids boil at lower temps when at altitude, but I feel this could have been avoided with proper use of the transmission and cool down procedure. What is the best way to cool down the transmission? In my Motorhome a huge loud fan kicks on and the temps go down. On the X is there a point where he fan kicks on to cool the tranny? Is it a zero pressure system like the diff? Does it cool faster in Park or Drive (or off)?

 

 

Is the fan in your motorhome electric?
Your stock Excursion fan is probably a clutch fan.

 

NOT GOOD FOR LONG / OR Just leave it in till the tranny goes South.


Many go to the 6.0 cooler to solve O/H ing issues.
If the truck did not run hot then the fan clutch is working fine.
The loss of fluid generally is from the seal over heating. You'll want to put in the improved seal (Vinton ??) upon rebuild
I would think in Park BUT I'm sure Mark will know for sure

 

I'd like to know more about the seal. I'm thinking it just boiled over. Isn't there an overflow? Did a seal really just fail? It's not leaking anymore and stopped immediately when it cooled down. I'd like to think we just need to manage the temperature better from now on. I'll post a pic of the transmission where I think most of the fluid came out.

 

Never ever shut off a truck with an overheating trans, it will cook it. If the temps get up to or over that 230 to 240 degree point then pull over and idle (or high idle) in Park until it cools off.
The system is a pressurized circulation loop from the trans through the water to ATF cooler in the radiator then into the air to ATF cooler then back to the trans. While pulling the trailer and the steep grades (in warm ambient temps too?) it sounds like you overtaxed the cooling capacity of the air to ATF cooler. A very popular upgrade to the cooling circuit on these rigs is to swap a 6.0 trans cooler for the smaller stock unit.
It is also pretty common for these 4R100 transmissions to have the front seal leak when overheated, then reseal upon cooling back off. There is an upgraded seal made from Viton that can withstand the high temps better without leaking, changing this seal over requires the trans to be partially removed. look for that job to cost around $400 or so depending on the shop. There is also a danger of having the torque convertor hub getting scratched or scored during these seal leaks, if that happen you are buying a new TC as the scoring will wipe out even a new seal.
Burnt ATF is never a good thing, a full flush is in order if the fluid is brown and or burnt smelling.

 

The seal gets soft when hot and starts leaking, then starts sealing again when it cools down. The upgraded seal does a better job sealing when hot.

As to cooling the trans you want to let it idle in park until the temp comes back down. If you shut it off there is no more flow or cooling so the fluid can't cool down. Not good for the trans.

Edit: WE3ZS ninja'd me with a more thorough answer as he usually provides.

 

I'd like to know more about the seal. I'm thinking it just boiled over. Isn't there an overflow? Did a seal really just fail? It's not leaking anymore and stopped immediately when it cooled down. I'd like to think we just need to manage the temperature better from now on. I'll post a pic of the transmission where I think most of the fluid came out.

 

 

There you go! The front seal that leaked when overheated is up inside that cover on the inside hub of the torque convertor. That's what happened, trans overheated, seal leaked, put on smoke show, cooled down some, resealed once seal cooled and contracted and now is working just fine. Classic case of front seal temperature failure. It MAY be fine from here out, but now if it should happen again you'll know what's going on.

 

Great, thanks for the knowledge. About the torque converter scraping, should I be able to notice it?

 

Not until it is removed. If you don't have any further leaking then you likely have nothing to worry about. A lot of people have had the front seal leak when backing up a hill, causing the trans fluid to get hot because there is very little air coming across the cooler. Once it cools down it doesn't leak again until they are backing up a hill again.

 

No, the surface of the TC hub where this leak prone seal rides is very smooth, and needs to be smooth and flawless. If any debris managed to work it's way onto that surface during the leak session it may score that surface. Once scored the seal won't be able to maintain a good seal and it will continue to leak some, installing a new seal onto a scored hub will have the same result and any seal will require a perfect surface to seal against. We are talking about "feel it with a finger nail" sized scratches here, very slight.

And this time Vwags ninja'ed me!

 

Good news is : From the drip in the pic the ATF does not look very burned. You should change it when you get a chance.

 

Cant the seal also go bad if the TC is on the way out also...I thought I read that somewhere. I had the same leak just not as bad and the TC gave up the ghost. Fluid still looks good and never got hot...