Here's the difference, the planetaries in the 727 are only running in the first two gears and can survive without much lube. The 518 planetaries are running almost constantly and need better lubrication.

Those who are sucessfully running type F in OD transmissions illustrate the old adage..."There's a difference between doing it right and doing it wrong and getting away with it".

As stated earlier ATF+4 is formulated for lockup converter clutches, not needed in a non-lockup 518 but it won't do any harm if you're not making tons of power.