Well, so this happened:

That's the result of coolant + transmission fluid (radiator mix). Luckily the mix inside the trans is milky but still feels like transmission fluid. The truck is a cousin's 2005 4WD Sport Trac w/auto if anyone is wondering.

Now, the radiatior is about to be fixed and reinstalled. I have a plan to clean both the coolant galleries in the engine and the transmission, but I'm kind of worried about the trans. I have transmission fluid (10qts) at my disposal to flush/clean the transmission before using clean/new fluid. Can I do 2 flushes with 5qts each? Not planning to run the truck like that, just reach operating temp, shuffle gears, then dump the fluid. You think I'll be safe with half the fluid necessary each time? Don't want to hurt the trans but would like to avoid adding even more trans fluid to the expenses. As far as I've been told this trans uses 10qts so it would be about half filled during each flush.

 

IMHO, I would plan on using much more....I would DC the cooler lines and using compressed air, blow them out, remove the thermostat typically located in a distribution block on the side of the trans and blow it out as well along with the lines, drop the pan R&R the filter, then flush the system...………….

 

The thermostat in these units is in the valvebody. According to Ford anytime the trans fluid is contaminated with water or coolant the trans has to be overhauled and every part with friction material has to be replaced. Apparently the coolant causes the material to delaminate.

 

The truck had water as coolant. The transmission fluid doesn't look as bad as the sludge from the engine (the one in the picture), it's milky, but still feels like atf. I already removed the thermostat, full of sludge up there too. I tried gasoline on the thermostat, its housing, and coolant hoses and it cleans them. Wondering if I can run the cooling system briefly with gasoline to clean it (probably not a good idea, but that sludge is mighty stubborn). I'm currently more worried about the engine cooling system than the transmission.

 

I wouldn't use gas for obvious reasons. When I was at the dealer the diesel guys would use simple green to flush oil out of cooling systems. Seemed to work pretty good.

 

Pardon the ignorance, what's simple green? I finally decided against using gas, didn't make much sense since someone said it. Simple radiator flush with refill/dumps with water has been working so far. The water is coming out cleaner every time.

On Edit: NVM, a quick Google search showed it's an all-purpose cleaner/de-greaser. It would have been a good help probably, but unavailable in Venezuela, thanks!.

 

Ok, so the cooling system is clean-ish (no visible ATF in any form during the last couple flushes, we did around ten total), and so is the trans, a couple of flushes with cheap ATF (it came out brown, then orange, then the usual red when checking the ATF after the test drive) then a refill with Motorcraft Mercon V and the truck is operative once again. Anyway, this is the draining/refilling procedure I followed during the flushes:

1.- Disconnected the transmission cooling line going to the radiator and connected a hose with a tight fit to it, placing the free end in a bucket to collect the ATF
2.- Turned the engine ON and let the contaminated ATF drain in the bucket until the stream stopped coming out continuously
3.- Checked for a torque converter drain plug, since there are none I skipped this step
4.- Lowered the transmission pan and removed the internal filter, letting the transmission drip away in a bucket for a couple hours (all the fluid drained summed up roughly 10 qts, which should be in line with the specs)
5.- Bolted the pan back in, torquing it appropiately to avoid crushing the cork seal
6.- Using a funnel in the trans disptick tube I poured 4qts. of fresh ATF
7.- Had my helper turn the engine ON and continued pouring fluid slowly, while he slowly changed gears
8.- Reached 8qts. total and the trans appeared full, the fluid apparently overflowed both by the dipstick and from the top of the trans. It could have been that I was a little too quick refilling, but I suspect the trans might be overfilled

During the test drive the truck seemed to work just fine, but I did notice some ATF came out the top of the trans (no pan dripping, no lose lines). I have no idea why but I think the trans might be overfilled, I will check the ATF level again after some light use (engine at operating temp while iddling in park) in order to discard an overfilled trans being the cause of the spills. I'm not familiar with these trans, but supposedly the 5R55E found in this truck is expected to take 10 qts. on a refill, so why just 8?.