Thanks all for the info. I haven't given much thought to most of the fluids on my truck other than oil and coolant (testing SCA's ect) for the last 40k miles or so. Did both differentials cause it's been 50k, and I had some water in both, and that got me thinking about the ATF.
I'm doing a DIY hydraulic ram steering upgrade in a few weeks and that will give me a flush of my PS, even though it looks great 50-55k thanks to the M1 synthetic ATF in there and the Magenfine filter I added. Just flushed brakes with a friends Motive pressure bleeder, but I do that every 2 years anyway, cause a quart of brake fluid is a small price to pay for keeping the system dry and clean. So that really leaves me only with coolant and ATF to be looked at. I know I can go a good while longer on my coolant, ph is good, SCA levels are where they should be, and one of these days I'll put my coolant filter back on the truck.
So on to the ATF, it seems that if I am understanding this right, the Dex3/Mercon specs are met by most of the house brand ATF's and should be ok even if they meet multiple specs like the Dex3/Mercon, and then say Dex 5 ect? Like I said earlier I knew for a while there Ford was very specific about not using Dex 5 in transmissions originally spec'd for Dex 3, but apparently that has changed, and now Dex 5 is OK? I'm guessing if a Dex 5 meets the Dex 3/mercon specs than it shouldn't cause a problem in the transmission. When I did the rebuild, I added the stuff mentioned, and used OE grade raybestos frictions, steels, ect for the ones that needed replacing, and went to the tight side of the specs. As such I think that's why I have such a cool running transmission. I mean even with my 37in mud tires and the "highest" tune my [censored] bully dog tuner has, I still run really cool. Triple disc billet converter prolly helps too, and then the added 10mic filter I make for a clean quick shifting 4r100 tranny.
I do tow off and on, sometimes heavy (up to about 10k), but its not like my truck is a work truck every day, I'd say on average I tow ~5-6k less than 10 times a year. Thought that might change if I decide to head to ND to look for work in the oil boom. I'd be picking up a 30foot trailer to live in before heading out that way. Generally right now most of the miles are highway, and given my almost excessive cooling, I don't know that I need to bother with synthetic, unless I can get a synthetic for around the costs of regular stuff. I'd need ~5 gallons, and I'd classify myself as unemployed (with no UE "benefits") and although I've been doing a good bit of mechanic work for people, but money is still tight. My Torque converter dosen't have a drain plug like the OEM one did :-( so I have to do the drain pan (has a drain plug on the pan at least) disconnect cooler return line, start truck watch for air, shutoff, fill pan, start truck till fluid comes out, hook up lines and then top off to "full". The extra 1/2 to 3/4 gallon of ATF buffer should be good, and besides I'll filter the old stuff it and pour it in my diesel tank for fuel.
As for what I can get locally, I have a Walmart nearby, Advance Auto Parts (seems that coupons don't work for ATF cept on some in quarts (like M1), Napa, Carquest, and a tractor supply. I can get to an autozone but it's a good 100 miles round trip from where I am at now. Hmm prolly should update my location. I used to buy 2 cases of Dex 3 ATF from Sams club, and call it a day. But I have no Sam's club membership anymore, and I don't seem to know anyone with a membership that could pick me up two cases of the "certified Dex3/Mercon ATF" they still carry. Price is pretty good at $2 a quart, so two cases would give me the 4.25-4.5 gallons I need for proper capacity, plus an extra 1.5 or so of extra flush thru the Tranny. Bout $55 with tax for 6 gallons of ATF isn't bad. Course the lack of a Sams membership kinda breaks that for me. Personally I like the cheaper Dex 3/Merecon stuff from Sams plus the recommended amount of Lubeguard Red. Pretty sure I did the Lubeguard Red back when I filed the tranny up after the rebuild.
Donald - I do have a lot of cooling, factory plumbed cooling in the radiator, then external air 15 or 20 row Ford factory trans cooler between the AC condenser and the inter-cooler, then plumbed right behind the Ford Oval in my grill, out in front of everything is a Tru-cool Max 4739 40k GVW fin and plate cooler. Before the rebuild I'd regularly see 200F even with all this cooling, now like I said it struggles to get above 140. For the late fall to about mid April I block the 40k cooler off completely with a sheet of rubber mat. Someday I might get off my arse and put some ball valves in to isolate the cooler when I dont need it.
You mentioned something about ST synthetic? I didn't even know that Wallyworld hat a ST synthetic that met the Dex3/Mercon rating, so I hadn't looked at the pricing. If the price was reasonable on 5 gallons of that I could justify it over just regular dino Dex3/Mercon or whatever house brand met the specs.
bmwtechguy - I like the sound of that Coastal stuff, $3.65 a quart isn't bad, and a synth blend would be a nice intermediate for fluid.
Of the few ATF related threads I have perused on FTE, Dex V appears to be fine in these now, as per a guy that worked on the design of the 4r100 and other Ford ATX's. Course I guess that opens up a whole other avenue of what to look at? With no warranty worries, and just my personal desire to get 170-200k+ before I have to rebuild again I want to make darn sure whatever fluid I am putting in isn't gonna give me issues.
Why the heck couldn't the powers that be just leave ATF and for that matter Coolant alone? it was so much simpler when coolant in just about every store was Ethylene Glycol - green or Dex-Cool, and there were basically 2-4 ATF's on the shelf.
