shoopfx4

Hey guys I'm new to the forum and have been having an issue with my stock f150 super crew 4x4 with 96000 miles. When taking off under load or shifting from 2nd to1st on a good hill my trans will grind then slam into gear. It doesn't happen all te time but it's enough to have me worried. Dealership said they can't do anything unless it throws a code or if they feel it when they drive it and of course they don't. Anybody have this problem or know anything that could be going wrong. Anything will help, thanks. Also, trans fluid has been checked twice and is good but I haven't pulled the pan to check for shavings.