Highway rumble

[Sdude2008]

99 3.0 5pd 4wd 170k
I’ve done some reading and do find some references to my issue but not much feedback and most posts are pretty old. Anyway recently I’ve noticed a rumble strip type sound at highway speed 55-65ish. It doesn’t happen while driving, only if I push the clutch in and it continues if I shift into neutral and coast, clutch engaged. Shifting back into gear with gas the sound/feeling goes away. I’ve seen some references in other forums but they refer to auto trans. I generally am not in 4wd at highway speeds and it doesn’t happen at lower speeds. The clutch and pp were replaced not long ago, flywheel resurfaced and pilot bushing replaced. Also u joints replaced. I also swapped in a used rear axle not too long ago. Same ratio but LS. Any advice is appreciated. TIA

 

[Sdude2008]

Update: the truck may have answered my question. While driving street speed tonight I picked up a cyclical scraping type sound. Upon inspection the sound if definitely coming from inside the drive shaft tube. I took a video let’s see if it comes through. Ok It’s hard to tell in the video but the sound is from inside the tube in the area shown.
I couldn't figure out how to attach a video directly. tia

 

[Sdude2008]

 

[SenorNoob]

That looks and sounds like a perfectly normal amount of play to me. Unless the movement it happening at one of the ujoints.

 

[Sdude2008]

I don’t disagree but its the noise while driving that’s not normal. Thank you for the input.

 

[SenorNoob]

I suppose you could try cleaning and lubing the slip joint on the driveshaft. Might notice something while you have it apart.

IDK what boot you might need, but the lube is Motorcraft XG-8. Rockauto is the cheapest place I found it. It's not a normal grease. It's much thicker and dries almost like latex paint.

 

[Sdude2008]

I ran the truck on jack stands and felt the diff front and back and yoke. No visible shaking or odd movement from either u joint but there is a distinct banging sound in the middle of the drive shaft almost like the aluminum tube has a shaft inside it. Next I’ll drop the driveshaft and do the slip yoke procedure. Is that slip shaft long enough where it could somehow be banging inside the ds tube itself? I added the video for the sound not the play. Thanks.

 

[Sdude2008]

I suppose you could try cleaning and lubing the slip joint on the driveshaft. Might notice something while you have it apart.

IDK what boot you might need, but the lube is Motorcraft XG-8. Rockauto is the cheapest place I found it. It's not a normal grease. It's much thicker and dries almost like latex paint.

Right best to drop the shaft and inspect everything. I like to ask here first in the event someone solved the same. Thank you.