2002 f-150 4.6 4x4 auto. Have a clicking sound that turns into a growl/howl at highway speeds.thought was a wheel bearing or u-joint.replaced rear u-joints,while rear was on stands turned driveshaft w/ trans in neutral and could hear/feel the clicking noise in the trans(about mid way),got louder faster i spun shaft.I'm thinking a bearing going out,but not sure...any other ideas.I do have a bad front wheel bearing/hub assembly,but that wasnt turning while on stands.thanks for any advise.
just a note,about a year ago dipstick tube rotted off and had dealer fix it,they removed pan,cleaned trans,new filter, tube/dipstick,new fluid,been about 15,000 miles ago.Also had dash apart a couple months ago to change heater core,wondering about shift cable maybe....truck has 115,000 on it now.

 

You might want to drop the pan and look for metal. Just throwing something out here, I don't know if this might be your problem but check the sonnax cure if your prone to high reving your engine.

Sonnax - Aftermarket replacement transmission, torque converter, and high performance automotive parts