Peterbilt / 6NZ Vibration

That .88 can make all the difference in the world. After replacing the levelingf rod on my Volvo, and putting it back in the same hole, I had a droning noise that would come and go, as well as an occasional growl out of the transmission. Lowering the suspension 1/2 inch did the trick... No more noise.

 

and yes it could be the driveline too .... when you let out of it the noise goes away because there is no torque or stress going to it .... could also be in the clutch ...IE throw out bearing.

 

Had the same problem took it to the shop but they could not find anything day next day same vibration but much worse come to find out bad u joint seems that the u joint was bad but needle bearing had gotten down in to end of cap and thus you could not feel any slack in u joint .

 

I have the same truck and same problem .Just recently I installed new clutch return spring it helped greatly.
My Question to original poster,If you put little pressure on the clutch pedal under load ,do you still feel the vibration? if not change the spring

 

That sound to me like a frt wheel bearing problem

 

if you have an 18 speed its your input shaft is worn