5.4 knocking
 

Just recently bought a 2001 f150 with 90000 actual miles. Oil change every 3000 miles.. Great truck but here is the bad it has a knock bottom end between trans and motor near the starter any idea of what it could be. Any suggestions would be greatly appreciated. Thanks

What engine is it? what oil filter is on it?
It can be a number of things, exhaust leak, piston slap, cracked flywheel, loose torque convertor ( presuming automatic trans), or much more catastrophic bad rod bearing or main bearing.
When is it most noticeable? 1st start up cold only lasting a few seconds?? Or after it is up to operating temp and at dead idle and goes away after bit of throttle is applied?? or it is there no matter what the RPM is at, warm or cold?
Have your oil pressure tested. Maybe even take a sample of engine oil and send it of to a lab. That will tell you if you have excessive metal particles.

A bad rod bearing comes to mind.

Mine has piston slap on start up, but only when cold out (32F-ish). Goes away in seconds as it warms up.

I found that switching to a thicker oil (10W30) and using a NAPA Gold oil filter helps to pretty much eliminate it. My truck has 371,000kms (230,000miles).

If yours doesn't go away when warm, it could be rod knock... I would try going with a thicker oil and quality filter before condemning it.

Chad