i bought a used 2000 v10 and want to change the transmission filter and then add a mag hytec trans pan. The problem is i have no idea what fluid is in there right now. My manual says to use mercon which is not a problem but what if the previous owner or someone else put in mercon 5 or something else??? i dont want to flush the tranny . what happens if the 2 different fluids are mixed?

 

Don't worry about it. The Mercon V is what you want to use becuse Mercon is no longer produced.

https://www.ford-trucks.com/forums/1...?highlight=ATF

 

i can get mercon under the brand name "super tech" at my local wal-mart. So i dont necessarily have to use mercon v.

 

Then pick one and stick with it. The Mercon V is better, but if you want to use the old spec fluid, knock yourself out.

 

i will pick one. however no one has definitively stated that you can or can not mix the 2 different transmission fluids which is still the original question i posted.

 

It will not harm anything to mix the current Mercon V with some Mercon in your transmission.

You'd be better off flushing it and getting out the most Mercon as possible, but it won't hurt anything.

 

Originally you weren't supposed to mix them, but Ford states you can mix the new in with the old, but its only recommended in the power steering or transfer case, not in the trans. If you have it done at the dealer or shop, they'll put Mercon V in. Its whats recommended now by Ford. If you're worried about mixing the old with the new, do a trans flush by following these directions. Changing ATF Fluid in a E4OD and 4R100 transmission .: Articles

Its written by Mark K, a former ford auto trans engineer. Another pointer, don't go cheap with the trans fluid. Replacing the trans is much more expensive then spending a few dollars more on quality fluid.