Mixing LV and SP Transmission fluids

[Berf]

I need to drop the transmission fluid and pan so I can replace a leaky bulkhead connector. This 6 speed (6R60) transmission calls for Mercon SP transmission fluid, which is no longer available. Ford now only sells Mercon LV fluid. I've read conflicting info on mixing LV and SP fluids together. Anyone have any good info on this? Can I just replace 6 quarts with LV when I drop the pan, or do I have to get the entire trans flushed out and replace all 12 qts with LV?

 

[Todd Z]

if your concerned you could use the universal stuff and be done with it or Amsoil synthetic...

 

[Berf]

I did a lot of research into this, and found a couple Ford TSB's about it. The early one said not to mix SP and LV, but they released a later TSB that now says it is ok to mix them. I dropped the pan, replaced the bulkhead connector, and refilled with LV and have not had any issues. The only thing I noticed is the LV seems to expand a bit more when heated. When I put in the same amount that I drained out, the transmission was overfull once it was hot so I had to take some out. I think the lighter viscosity (LV) expands a bit more than the old SP did.