when decelerating my truck vibrates and makes a kind of grinding noise... it does it a little bit while accelerating. it did that for about a week
now it just makes a lot of sounds (clinging-ish) when im accelerating, it doesnt do this when i let off the gas.
would this have something to do with the rearend or driveshaft or what? BTW: my clutch is going out, could that be related?

also when starting/or going after shifting into 3rd it makes a "clunk" kind of noise, its been doin this 4 a while so i dont know if its related.

 

Sounds like rear end problems of the major variety, although it might be the u-joints.

fordmando
70 F-100 400 C6
78 F-150 4x4 400 NP435
George Selby

 

Sloth,
Your describing U-joints. The driveshaft misalignment could cause a vibe. U-joints make a clicking/grinding noise when they go. The clunk to 3rd gear? Is that when you shift into it? Or after you let out the clutch?
KingFisher

 

Block the wheels so it won't roll away, leave it in neutral, and get under there and have a look. Wiggle and twist the drive shaft. If you have a splined slip joint, make sure there is no side play at the joint. Twist the drive shaft and look careful at the u-joints for play.