I guess this is really a matter of opinion but......I am taking my truck to the dealer for the 30k mile trans service. Should I go with synthetic fluid? My hauling and towing consist of my little boy's Yamaha 80 and an eight foot trailer with a scoop of mulch or gravel about once or twice a year.

Also, I have read all I can about what people prefer but what is Ford's recommendation for changing the transfer case and diff fluids? I may have missed it but I didn't see it in the maintenance schedule portion of the owners manual.

And just out of curiosity, does a limited slip rear diff require a different fluid than a non-LS?

Thanks guys

 

1. I prefer synthetic but it's not necessary, standard Mercon V is part synthetic to begin with.

2. I'd do the transfer case and rear every 100k or sooner.

3. Same fluid - 75W140 synthetic for both - but the LS requires a bottle of friction modifier too.

 

Hey, thanks for the info! One new question based on your answers.....does the diff come from the factory with the synthetic or is that just what you recommend?

 

Factory fill on a 03 is 75W140 synthetic in the rear and 80W90 dino in the front. Synthetic is *required* in the rear as per Ford. I'd personally use synthetic 80W90 or 75W90 in the front.

 

Right at about 3,000 miles, I had my dealership swap out to Royal Purple for the engine, transmission, and differential. The tech at the dealership had a big grin and said that more people should put that stuff into their trucks. My dealership was cool with it, and encouraged it. I give them - 2 thumbs up. Some dealerships will tell you that you are voiding your warranty because you are not using Ford's fluids. I give them - the finger.

 

True... very true.

After all, it is YOUR truck... not Ford's.

I like RP fluids... expensive... but they hold up to their name.

 

The Motorcraft Mercon V your dealer will use for the transmission service is fine, especially if you plan on doing services every 30K. Synthetics such as Mobil 1, Redline D4, or Amsoil can allow you to run longer than 30K. They cost roughly twice as much as part synthetic Mercon V but can handle heat and oxidation better. Ask your dealer how much the transmission service cost using their fluid and how much it would cost if you bring your own. Some dealers will charge you labor only if you bring your own fluid, some charge you the same regardless of whether or not you use their fluid.

 

I, too, have changed all fluids out to Royal Purple...The shifts are nearly undetectable...the truck seems to have more power....RP is a bit pricey....but...IMO well worth it...

 

Put on a tuner, and get even more better shifting

 

I've got royal purple in my Z (see sig..) Definitely worth the cost. Rear diff was kinda lacking before, since the purple it's really smoothed out.

But, like Steelers said, the factory stuff ain't bad.