Boneheaded mistake - tranny fluid

[ogre01]

Well, I serviced the transmission this weekend. Parts store was full, and I didn't have my phone, so I read the back of the bottle of Merc III, that said don't use in "2008 and after" models, there was no Merc IV or V; just the newest VI. I guessed I'd used Merc III last time and headed out. After changing filter, putting it together, pulling the dipstick, adding fluid... I picked up the dipstick and read the very clear "Merc V" at the end. Bonehead.

So, what's the steps going forward? I did some googling and found a guy who just uses merc III with an additive in all his Fords (nothing "new", but all more modern than my Town Car), keeps it clean and has not had any issues (going on 500k miles on his F150). Talked to brother who is a very qualified shad tree, but only ever uses factory spec and brand fluids; he wasn't too concerned, just feel for driveability and Town Car shudder. (<- this is really funny, I have it typed capital T and C, forum is autocorrecting to Town Car (rather than the torque converter it means)

Currently I'm driving as normal, have not put any additive in; in a variety of conditions (high highway speed, cruise speed, town speed) everything feels fine. Any informed opinions?

Thanks all. Also, Happy New Year.

 

[Action]

I am not clear on your post above as to what you actually used.

Not sure I have ever seen Mercon VI. But in the progression of Ford ATF, Mercon VI would be Mercon LV.

Mercon V is a best fluid for that year for clutches and valves. Especially during cold operation and initial cold use.
It is also backward compatible to the original/older Mercon fluid line.
If you installed Mercon III or IV, I would just drain and refill. If possible, drain the converter as well and blow out the cooler and lines. The idea is to get as much fluid out as possible. There will be some residual fluid, and over time it will not have that big of an impact.
Those previous editions of Mercon can work. They are all compatible as far as viscosity. However, at different times under certain circumstances the shift qualities may be a concern because Mercon V was not used and Mercon V is the better lubricant. Plus, it has a better additive package for later transmissions to aid is shifts.

If you installed Mercon LV, (Or previously SP) there can be more serious issues. It is NOT backward compatible. These fluids are too thin for older transmissions.
The same applies to ULV which was only used in 2014 and later transmissions.

Action

 

[ogre01]

I used Mercon III. Put about 5 qts into the system. Fortunately I've never used LV or any of the "modern" versions.

 

[Action]

The entire transmission capacity would be greater than 10 quarts. Some of those transmissions can have close to 20 quarts.
Most of the oil/fluid is in the torque converter. Maybe double of what is in the pan.
Plus a quart+ is in the cooler and lines.

Five quarts was what was likely in the pan only.

I have never had a major transmission repair. (Well I did in the 70s with a Cast Iron Cruise O Matic in a 64 Galaxie)
All of the FLM vehicles I currently have (except a couple of classics) have over 200,000 miles. Including my wife's non-Ford product.
Fluid service is just one piece in keeping the mini-fleet running down the road.

Action

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[Action]

I used Mercon III. Put about 5 qts into the system. Fortunately I've never used LV or any of the "modern" versions.

Damage to the transmission bushings and valves isn't going to occur with Mercon III in your transmission.
It is shift quality that may be an issue. How the friction material reacts to the older fluid type.
Because you only changed out 5 quarts, you now have a mixture between the two fluids.

Action

 

[driller]

I wouldn't be able to sleep without draining everything as much as possible, torque converter included, and refilling with Mercon V.

Transmission fluid is not cheap but it is certainly cheaper than any future transmission repair.