I recently picked up a 99 navigator. It has the A4WD mode. Anyways i did try searching and it seems my issue is a little different than others.

When the truck shifts into 3rd gear, and sometimes overdrive, it feels like theirs some chatter out of the rear end. It feels like im driving over a rumble strip only when it shifts. Defiantly coming from the rear area.

Any thoughts?

 

noone has any ideas?

 

Its a trans shutter, ive had a few F150s do it. Change the trans fluid and filter and it should go away mine always did.