Squeaking When In gear on a 92 D250 12 valve

What is your question?

My 92 d250 12 valve is squeaking only when it’s in gear. If I take it out of gear and let it roll the sound stops. It’s not a belt, the alternator, or the transmission it sounds like it’s in the middle to back of the truck. I’ve checked the driveline and all the caps appear to be attached and it’s not not loose at all. I think it something to do with the driveline or something attached to it because it only makes the noise is I’m in gear and it’s moving the truck which makes it hard to pin point exactly where it is coming from. Thanks you for any help you have

What makes this problem better or worse?

Get louder and faster the faster I’m going

How long has your 1992 Dodge D250 had this problem?

Few days