Title. I read on the internet that “once you open the cover to the filter” (aka the transmission pan) “the filter must be replaced because the surrounding seal will no longer seal properly.”
Specifically on a 05-14 mustang…
Is this true or just a bunch of nonsense
No, You don’t have to replace the filter.
But if you dropped the pan, you should. Filters are cheap.
Some vehicles don’t even have filters. Don’t have to change filter…but it’s probably a good idea…At least every other fluid change.
I would never NOT change the filter with the pan off. If the bottom of the pan has some degree of sludge in it then that is even more reason to change the filter because odds are some of that gunk is clogging some of the pores in the filter which in turn restricts the fluid flow.
I think that info you posted is sheer bunk.
