Ford 6r80 transmission overheating on track after fluid swap - mercon L to LV the culprit? fluid recommendation? dying transmission?

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Apr 1, 2022
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So I had 20 quarts of fluid run through my car at Ford Quicklane as part of my seasonal maintenance.

According to Quicklane, the part number was XT-10QLVC for the swap, and it's Mercon LV.

I looked it up, and it apparently replaced some XT-12 fluid for all Ford transfer cases.

The car never had a hot transmission with the old fluid, and it's now getting hot and throwing me out of Sportshift mode after ~15ish minutes at high speed and I believe this fluid may be a culprit.

Does anyone have any idea what the viscosity would be and/or recommend a replacement fluid to circumvent this issue? Thanks!
 
Vehicle? Year? Mileage?
Is this the trans first service?
It is common for supplemental ATF cooling to become needed on track, especially as newer drivers start getting faster and pushing their vehicles harder.
 
Its 145k miles. I've been de4 for 4 years now and the problem came up immediately after the last service. its been serviced once before at 100k miles where they used 10 qts to flush it and said the fluid was still black so hence I'm really onto the fluid atm
 
I checked it today. It was actually a touch high. i initially pulled the stick with the engine off to make sure it wasnt jammed up or anything and fluid actually popped out of it. cranking it sucked it down. its either tip-top full or slightly overfilled
 
So XT-10-QLVC is the part number for a quart bottle of Moercon LV. The Transfer Case Fluid came out when regular Mercon was replaced by Mercon V and Mercon V was not rated for most transfer cases. I do know the 6R80s run a bit hot, they have a thermal bypass for the cooling system to keep them hot.
 
Theres a dipstick?!?!?!?!?!
..Yeah. The 6R80 has a plastic dipstick inside the 19mm(?) cap you unscrew to fill the trans.


IMG_20210518_164352-COLLAGE.jpg
 
..Yeah. The 6R80 has a plastic dipstick inside the 19mm(?) cap you unscrew to fill the trans.


View attachment 101192
I replaced that dipstick with one from Performance Automatic that goes up into the engine bay for my 2014 Mustang GT. I also bought another factory transmission pan and had a drain plug welded in where the pan has that protrusion in the bottom of it. Makes changes and checks so much easier.
 
God-dangit Bobby.



I think a joke was missed. I wrote about checking the fluid level and you cant help but find a stick under that plug after you burn yourself on the catalytic converter (even with mechanics wear gloves) trying to check it after setting your car level on jack stands.

I was advised for my purposes to get the fluid about halfway up the hot check on the stick and removing nearly a quart got it to about that spot.

it's a pain in the bunghole.

btw every one of those standard dip stick tubes I've seen added on in the muscrat community leaked.

any luck?
 
Humph.

The top picture of the two levels i posted is supposedly where you're supposed to line it up whilst running when the oil is less than 100F. ie. a cold check if you will.
 
i assume A is for cold and B is for warm, and your problem went away when you took some fluid out so that its in the middle of the A when warm?

its hard to think that one extra quart would be all it took to throw the transmission of that mode..........how many quarts does it hold? i would think the trans, torque converter, trans cooler, all the stuff associated with the trans would be that much effected by one quart but....... i guess its that sensitive, or that fluid expands a lot more than I think.

i guess if i did some simple math.......... let say it held 10 quarts, each quart at 230*F expanded 10%.......... so now, 10 quarts has been expanded to the volume of 11 quarts............ and lets say theres no room for another quart in the system...... so much that there is a sensor that will come out of the steering wheel and slap you if you do.......... makes sense
 
Ford never actually specify, even in the service manual, what A and B are for, they want you to check and adjust when it's running at full (195-205) temp and the level is written as the top of the B area. I think it's about 12, 13 quarts or so for total capacity.

The fluid does expand a lot, particularly the Motorcraft stuff apparently.

The going over the level will result in overflow from the fill hole when the oil is up to temp and the engine running. If it was filled when it wasn't full hot and the engine was running, it would drop the level enough to allow room to put much more oil in without overflowing the fill hole.

Important, i do not mean it's possible to use the fill hole to measure the right amount - oil at full temp, engine running, correct level is a few inches below the fill hole - just turning off the engine will bring the level up very near the fill hole.
 
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