i own a 2001 ranger edge, 3.0, 5speed with no major modifications other than i had to do an axle swap when i sheered the teeth off my pinion gear. now it has an 8.8 ring gear. anyway i recently replaced my clutch, pressure plate, and pilot bearing. when i refilled my trans i made a stupid mistake and didnt read closely, i put mercon5 in and the manual says mercon. now i have a winding/sliding (sounds like oily metal rubbing together) noise in second when i am moving. i was wondering what kind of damage happens with that? why dont they mix? i cant find a difinitive answer anywhere. ive only driven about 2000 miles on it that way should i switch it back asap?

 

Well, I don't know all of the aspects of the different flavors of Mercon but I have read that Mercon V has a friction modifier that, when used in an A/T designed for it's use, is needed to stop T/C shudder. In fact, the article stated that the only difference between IV and V was the addition of this friction modifier.

 

If your vehicle calls for Mercon you can use either Mercon or Mercon V. If it calls for Mercon V you must use Mercon V. It is because of the Friction Modifiers and a couple of other small things that I can not remember right now. Ford has the strictest standards for ATF and always has. There is some lead parts in the AT's and without the Mercon V, they will eventually start to stick.

 

I wouldn't worry about it causing a mechanical problem. There are people who use Mercon V in their manual transmission by choice. But if you feel it might be contributing to the sound, simply drain it out and use regular Mercon.

It's much more important to use the "correct" version of Mercon or Mercon V in an automatic tranny, with line pressures and special clutch packs and things like that.