- Jan 25, 2022
I recently changed oil in my 1997 F350 (60k miles) with a ZF5 and a 2004 F250 (120k miles) with a ZF6 manual (both gas engines). Both of these operated and shifted flawlessly before and the fluid changes were both done as preventative maintenance. I filled them both with Amsoil Torque-Drive syn ATF. Afterwards neither one shifts as well and are especially hard to get into gear when cold. Also the shifts now feel clunky like the fluid is thin and the shifts feel borderline scratchy. I feel I should change to a different fluid or add something but what?