Hello to all. I have a former military vehicle that uses 15w40 in the Allison 1545 auto trans. I'd like to drop the pan and do a filter change also change the inline cooling line filter. What would be a good choice for replacing the fluid (6-7 qts) knowing that 15w40 formulations and add packs have changed so much over the years. The trans was manufactured in 1994. API CD - CF was probably used as the factory fill. No interest in going to ATF as I have been told that in many cases it can cause significant issues. Thanks to all. Pics of truck.