Time to change out the tranny fluid on my '03. Who has some info or opinions on synthetic tranny lubes ?? incl. transfer case and frt & rear diff's

 

I run Mobil1 Merc V full syn in my trans. Been in there for a few years now. Good stuff -- about to pull a sample and have it checked at BlackStone in about 4000 miles. Will post results when that happens...

 

Definitely the Mobil 1 full syn. Trans even shifts smoother with it, not lots, but enough that I noticed the difference.

 

If I recall correctly, John Wood told me over the phone that we should not use synthetic, or even Mercon 5 in our transmissions. Just plain old Dexron3/Mercon. I think he said his or a BTS can take synthetic, but it isn't any better for them. I hope someone chimes in on that if I'm wrong. As far as the rear diff, 75w-140 synthetic is recommended. Front diff 75w-90 dyno is what the book says, but I think syn is fine.

 

Mercon 3 isn't available anymore. Mercon 5 was reformulated and is now OK for our trannies. Maybe Mark K. can weigh in on this and the Sythn issue. I know it was discussed before.

 

I found this link as well.
https://www.ford-trucks.com/forums/4...n-fluid-2.html

Not sure if the link will work, I'm kind of challenged that way.

 

in on this because I'll need alot to refill my trans with the MagHytec pan.

 

me too!!!!
I am also running a TRU COOL HD trans cooler and Magnefine inline filter

 

Save some $$$ and put the stock pan back on. The larger pan has been proven to cost a lot more than it helps.

And syn is perfectly fine in our transmissions. I'm a firm believer in syn fluids -- to the point that every fluid in my truck is syn. Handles heat and cold better, lasts longer, and worth it in my book.

 

Izzy, what brand of synthetic fluids are you running in your truck?
just curious!

 

A mix. I run Syn Rotella in the engine, Mobil1 Merc V in the trans, Royal Purple in the diff, and Valvoline Dot 3/4 syn fluid in the brake lines. I also run aluminum complex grease in my bearings instead of lithium -- better moisture content resistance.

 

hoe do you like the RP in diffs?
I usually use Mobile 1 gear oil

 

There is NO reason not to run synthetic ATF. It can't hurt the trans anymore than any other ATF.

My favorite ATF is Mobil 1 synthetic ATF.

 

I agree with Mark, even BTS puts Schaeffer's, or Amsoil.

 

Brian at BTS uses Schaeffer's. After four+ years and 25K miles, it looks brand new.