2008 Ford Explorer shift problems

If it's making a whistling sound it cold be engine but jus tto be sure have a trans guy check this out it may be a reaction carrier that has worn out and making the noise as well as being low on fluid. It has to be checked with engine running on a level surface so easier done on a hoist. There is no dipstick any longer. A reaction carrier is a planetary gear set and just one gear in there can be worn causing the noise. But it cold be low on fluid again sucking air causing pump to make the noise. See pic for planetary gear and disregard the black arrow.