I have a 07 Silverado with a 6.0 and a 4l70 trans. The truck runs about 10k miles a year with heavy city driving with moderate loads and no towing. At 5k miles I installed a Perm-a-cool in line filter and have a Wix 51515 filter. The filters are only about $4 from Fleet Filter so I will be changing them at my 6 month OCI. I also plan on fluid changes every other year with the trans cooler line method. I have read a lot of posts saying the factory trans filter is not very efficient. So, do you think I will ever have to drop the pan and change the factory filter ? The transmissions in full size GM trucks seem to be a (carp) shoot. Some guys are changing trans every 50k and some run for ever.