Royal Purple Synth

[mnkeeking]

So here's the $64K question: I have a '68 F100. PO swapped out the factory 360/C4 combo for a 460/C6 combo. All good. PO did so scrounging parts from various engines and trannies. All good. I bought the truck from a "buddy" of the PO who told me the PO needed some cash. What I think is the PO "sold" the truck to his buddy 'cause he was strapped for cash and never got unstrapped. Buddy then gets tired of the old truck taking up space in his up-scale Orange County (CA) driveway AND buddy doesn't know much about working on stuff. So buddy puts truck on craigslist 'cause PO is broke. I know the truck sat in buddy's driveway for about two years. It was started whenever the buddy wanted to piss his wife off or got a wild hair. He kept the tank on empty, had 4 different tires on it (one of which was an ice tire with the cleats you can screw in. I dunno where he even FOUND one of those.) Anyway, long story short, this is where I come in. Bought the truck, started fixing things (gaskets were all cracked, rubber was wasted from sitting in the sun, etc) but because the buddy didn't know much, I've been making informed guesses when I order parts. Luckily, the 460 was produced for a LONG time and didn't change much. I've got the motor nailed down, am keeping a list and pix of parts I replace, part numbers, etc. Just started going through the tranny. I've assumed that I should be using Type F in the tranny because it could possibly be older than the motor and I believe Ford produced C6s in that year range. There are no external tags on the tranny to help with id, it is a 17-bolt 3-speed C6 AT, but when I dropped the pan yesterday (and the pan may not be the one the tranny came with) I noticed a stamp on the box the new filter came in that said Mercon was the recommended fluid. I want to run full synthetic Royal Purple in my motor, tranny and rear end and here's my question, finally. In everyone's opinion, should I use the RP Max ATF, which states it's not to be used in trannies requiring Type F, or should I use RP Racing ATF, which states it's a Type F, but doesn't contain as many modifiers? Anybody running RP or any other synth in their ATs? Am also working on fabbing one of Springerpop's external tranny filters for added insurance. Need a little guidance, here, I can't find an old-school parts counter out here to hang around and ask questions, and my pops is 2500 miles away.
Thanks,
Joe

[averagef250]

The way it was explained to me is if your transmission still has seals and frictions in it from the 1970's you would be best to use type F. If it's been rebuilt in the past 20 years you use ATF3 (dex3, whatever you want to call regular old ATF).

FWII Type F is supposed to be better fluid. It helps the frictions grip better and last longer.

FWII I find you can dump whatever fluid into crappy older automatics you want and you get the same results. Tractor hydraulic fluid is about $45 for 5 gallons at auto parts and farm stores.

Synthetic anything going into an old truck like these built around 1940's technology sure seems like overkill, probably even detrimental. The crappiest oil you can buy today is 1000 times better than the junk that was refined before things started changing in the 80's.

[Donnie]

Mercon, Dexron, pick your # are all modified fluids....which really means that they are a bit more slippery than type F....
Unless you are building a complete trans, which I assume that you are not, I would use Type F.......this fluid has the ability to grip the friction materials a bit more agressively than the modified fluids....Fluid tech. has changed BIG time in the last few years.........Donnie

Stay away from store brands.......Use good fluid