Planning on swapping in the 6.0L trans cooler tonight and imagine I will need to top off the trans fluid. Should I use regular Mercon or use Mercon V? I know the trans was serviced about 10K miles ago by previous owner but I don't know which fluid is in it currently. Not interested in flushing everything at this time.


Can Mercon and Mercon V be mixed? I am seeing conflicting info online and figured this is the place to get a straight answer.


Thanks!

 

Merc V is the only recommended fluid so far as I know. Personally, if it's financially feasible I'd swap all the fluid out to provide a baseline and so you'll know just what exactly is in the trans.

 

Thanks Matt for the reply, I don't have time to do a complete flush and based on the horror stories I have heard about problems afterwards I am hesitant.


Looking in the factory service manual regular Mercon is what is recommended. I believe Mercon V replaced it sometime later.


Would I be able to tell which fluid I have by looking at the dipstick?

 

Use Mercon V. You can mix them, but if the PO used Mercon, you should do a full flush. Mercon ingredients aren't controlled by Ford anymore and you don't know what you're getting.

Good information (from Ford) here: https://www.fcsdchemicalsandlubricants.com/main/

I did mine in an afternoon. No horror stories and no problems.

True and Mercon V was changed after the manual was printed. Your trans dipstick says "Do not use Mercon V" but all that is out of date now.

Nope.

 

Those old horror stories about flushing a trans don't hold a lot of juice anymore honestly, technology has surpassed those issues. Swapping from a nondetergent to a detergent oil sure, but you won't run into that nowadays.

Mark K recommends Merc V, and seeing as how he used to design and build these trans as an engineer I take his word above anyone else's.

You won't be able to tell looking at the stick, it's all red visually.

 

Mark K is certainly THE authority on the trans, not questioning that at all. Just looking into the options as I certainly don't want to cause damage.


The right thing to do would be to change the fluid while doing the cooler. Need to see if I can steal a friend as after reading Marks procedure it is certainly better to have two people for the drain portion.


Thanks for the info, wish these mods were more straightforward but this forum is awesome for getting good info!

 

Mod's are always straightforward, remove old and replace with shiny new!

It's all the stuff in between removal and replacement that causes issues

 

Matt you are spot on!


So I was thinking about this some more and recalled that I had the Carfax from when I bought the Ex. I found the service for the trans flush and called the dealer where it was performed. They were able to give me the part # (XT5DM - 55 gal drum) for the fluid they used and I verified it is in fact Mercon V. So as of now I am going to just top off the fluid at the time of the cooler install.


Thanks again everyone!

 

As others have stated, Merc V is what you want.

I'm way too skeptical to believe any supposed horror story regarding fresh fluid ruining or causing the "early" demise of any 4R100 trans.

Stewart

 

Stewart, thanks for your reply. I am not against a flush but after finding the Ex has Merc V in it now topping it off with the same should be fine. The flush was done at 38K miles and I only have 53K on it now. I don't think it needs a flush again as everything looks good and I don't want to waste money.


I just found that with the V10 the cooler lines go to/from the radiator so I have short lines. Cant find any info on splicing the 1/2" to 3/8" lines but I will make it work.

 

Yeah, when we (7.3L owners) and V10 owners upgrade to the 6.0L trans cooler, adapters need to be fitted.

I think I have a link to a write-up in the tech folder, or it's possibly a write-up on one of the members tech help pages I've linked to at the bottom of the last post in the tech folder.

Stewart

 

It's in the tech folder, was looking at it earlier today prepping for mine.

 

I used the article in the tech folder and it helped a ton, great to have the resource for sure. I have had the cooler and necessary parts for months and decided to get it done. I elected not to remove the bumper but should have, would have made accessing everything easier.


Overall the install went OK, just took longer than I was planning...as most projects do. I lost a little over a quart of fluid during the swap I believe and put two in once complete. I need to get the trans warm and monitor the fluid as I think I might be a little low as I have read the 31 row cooler holds a quart or two more than the factory V10. Anyone have any insight on the fluid amount? I also can never get a good reading on the dipstick, tough to tell what the actual level is vs. fluid from the tube getting on the dipstick itself.


thanks again for all the help

 

I can sympathize with the hard to read dipstick on these. If you can get a good reading where you can tell where it is, one side of the stick will seem to show lower than the other side every time. Which one to believe? .

 

And I thought it was just me. Is there an aftermarket dipstick available ? Maybe dye can be added? I hate to look like a reject, but I have never in my life had a more impossible to read dipstick than the one in my Excursion.