Title kinda says it all. Accidentally did a full transmissionmission fluid exchange with Motorcraft mercon LV instead of V. Didn’t read the bottles till afterwards, so it’s full of around 18 quarts of the stuff. Truck has around 250k on it, not sure if the transmission has been replaced (it has to, I don’t think many of them make it 250k without transmission work). Pan had some very fine metal in the magnet but no clutch material in the pan at all. I have no idea what fluid was in it, other than it wasn’t burnt and still had some red to it. Truck has been driven about 10 miles, shifts just as good if not better than it did before. I’ve gotten mixed responses, people saying get it out now and hope you didn’t burn it up, to people saying they used it in a unit behind a 7.3 turned up to 500hp and haven’t had any issues. The hive mind seems to like the Maxlife Universal, which is also rated for V AND LV applications and has a very similar viscosity at 100C, 5.9 Cst vs 6.0 for the motorcraft. So I don’t know if I should just drive it and not worry about it, or bite the bullet and spend another $150 on fluid to change it out again.
Mercon LV in old 4R100
- Thread starter tagman31
- Start date
Worry about it if you notice anything other than improved performance. I’m betting you won’t 
I would change it to Mercon V if it was mine. Not based on specific evidence, but just for peace of mind.
Well this makes me feel a little better, on the ford truck forums all I got was doom and gloom. I’m going into with with the mindset that if modern maxlife that’s V/LV rated is just fine, so is straight LV. I don’t see how the valvoline fluid can meet both specs anyway.
I would only be concerned if the fluid is overheating (thinning out) but it's basically the same just a little thinner. Would be similar to changing 5w30 to 5w20, same wear protection it's just a little more efficient at the cost of limited high-temperature protection.
LOL I literally started to type yesterday "step away from the internet" but then decided I don't REALLY know all the nuances between V and LV (and neither do the internet warriors telling you the sky is falling)
If it were me: since the transmission is performing as good or better, I'd leave it and find something else to worry about. Do you have a pan with drain plug? You could always just drain the pan every other oil change for awhile. If you shop carefully like RA or watch for sales, Merc V isn't that expensive
I rolled the dice and have put about 200-300 miles on the truck since the change, and I’ve only noticed improvements. Shifts are smoother and quicker, TCC lockup has improved, and it will spin the back tires if you floor it from a stop, which there was no chance of this truck doing before it was flushed, the transmission was incredibly lazy. I haven’t been nice to it, so if it was really as dire as that post says, I would have had a problem by now. I just did an hour of creeping in traffic yesterday, 1-2-1 shifts, and no issues.
Sounds good to me. Keep us posted of any updates?
Nice. I’m lucky enough to have a drain plug on my 4R100 pan and just did a second drain and fill at 183k miles. Used up the MaxLife and finished off with 2 quarts of Valvoline Restore and Protect ATF. Will use that exclusively from here on out.
Put almost another 2k on the truck. No issues to speak of. Fluid still looks good, like the day it was put in. Turned the normal red color that Mercon LV is known for after a few thousand miles. I did log some live data and torque converter slip number is good. 0.5-1.5 RPM, which is excellent for a truck with this many miles and comes down to error in the calculation in the PCM. It is not slipping in "real life", no shudder. Shifts are good, firm, and quick, no delay between drive and reverse like the 4R100s are known for. No delay when asked to kick down. I'm assuming the transmission has been rebuilt at least once. Miles on the dash is 237k, the Carfax I had a friend at at a dealer run tells a different story, more like 275k-300k.
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