Hello everyone happy thanksgiving. My name is Vinny and I’m a new member so I apologize if this is a commonly asked question.

I drive a 2004 ford econoline with a 4.6 liter v8. I’ve replaced the exhaust manifold and gaskets either side, cut out all cats and welded in straight pipe with 02’ sensor spacers to avoid a check engine light. I’ve changed the rear differential fluid and do oil changes. I keep up on the van and it treats me great.

today while driving, when accelerating and going down in gear in the highway, I’m hearing and feeling a slight clunk of sort when hitting the gas and causing the transmission to down shift. I was looking for some pointers here in where to look and how to diagnose this new issue. Thanks. My father said maybe it’s a solenoid on the transmission. My first thought was a possible u joint issue in the driveline. I’m all ears. Thanks I’m advance. I believe it’s making the noise when going from overdrive to 4th gear?

 

Before assuming anything, it would be a good move to check the U-Joints in the drive line.
If original ,they have no provision for lubrication and do wear out . When they do , they can provide squeaking, vibration, and clunks when placed into gear or whenever the load on the driveshaft is is momentarily reduced or applied.
Looking at them does nothing , they need to be checked when load is applied or they show signs of rust.
If all that is good then a check by a good trans shop might be required.