Peterbilt 379 vibrating .need help !please

Check the spline on the slip thru drive line. I’m referring to where the drive line meets together. Push it up and down and check for excessive play on both drive lines

 

With any vibration that changes on a accel or decel always check and set suspension ride height to spec. It the easiest to check and adjust first. Its also easiest to get outta wack a bit without noticing visually.

Where is the vibration? Seat and feet?

 

X2 on ride height. Solves most things. Any recent repairs to the driveline? Problem just start all of the sudden? Is it a hop, growl, shake? Pete ride height specs attached. What type of suspension do you have?

 

Carrier bearing?

 

If the previous solutions don't find the issue check to see if you bent the driveshaft, that's about speed range where a twisted shaft vibrates the worst.

 

Check that you re-installed your driveline properly. If your u-joints are not inline, she'll vibrate .

 

I agree with the post saying to check to make sure that your u joints are all lined up properly

 

if you have balloon steer tires, check air psi. very common if air out 5 lbs.
or, even as simple as mud stuck inside the wheel rim, if youve been in mudeetc (its that time of year, mud mud mud)