Vibration

[Stacyb]

Mack 2013 ch613 vibration starts at 50 gets better at 70  driveline balanced new u joints does it bad when loaded trailer at 50 to 60 new tires didn’t change this balance didn’t help feels like it’s in floor then sometimes like seat little in steering at times new back motor mounts  any help would be greatly appreciated 

[fjh]

19 minutes ago, Stacyb said:

Mack 2013 ch613 vibration starts at 50 gets better at 70  driveline balanced new u joints does it bad when loaded trailer at 50 to 60 new tires didn’t change this balance didn’t help feels like it’s in floor then sometimes like seat little in steering at times new back motor mounts  any help would be greatly appreciated 

Air suspension? Ride height ?

[Stacyb]

Yes air ride will check height does it need to be checked loaded or unloaded

[fjh]

Tire need to be roughly 3/4 to 1 of an inch below the top frame rail loaded or not! There is a proper gauge for this how ever this is a get by! Experiment with it! There is an 18 mm head bolt that holds the ride valve to the frame  loosen and tweak the bracket. And tighten bolt the bags and refill and check the height it’s easier if you on a flat slab and measure from the slab to the frame at the back it’s all doable from the outside!there is usually a hole you can bar through to change the mount bracket height!

[Geoff Weeks]

Air ride should be about the same loaded and un loaded, that is one of its claim to fame.

If any rear suspension or frame work has been done (lengthening or shortening) check driveshaft angles. Also make sure the U joint is in proper phase with eachother. If a new jack-shaft was added to the driveline (for longer frame) make sure it is at the same angle as the transmission or the forward jackshaft. (most often pitched down between 2 and 6 deg).

Drive axle out of align can act like a tire out of balance and will eventually wear a flat spot in the steer tires, but is generally smooth with new tires and gradually comes on as they wear.

 Next, pull the 1/2 shafts (axle shafts and run it up to speed in top gear and see if the vibration is still present, If the driveline uses jack shafts, you can drop out the shafts one by one (starting at the back) until the vibration stops when run up to speed. Also (CAREFULLY) hold you palm near the spinning shaft to see if there is run-out your eyes can't see. It doesn't take much.

Lastly measure the drive shaft sections yoke to yoke and working length and plug the numbers into Spicer's calculator to see if you are getting the vibration at 1/2 critical speed or if any sections are running near critical speed when you get the vibration. You'll need to know how fast the shaft is turning when you get the vibration. If top gear is direct, that is easy, just read off the tach, if not, you have to multiply by the O/D ratio.

[Mackpro]

Here’s the bulletin on ride height setting. Covers all but the Mack “Y” ride suspension. Read it carefully and match up what suspension that you have. Also does the truck have a sleeper? https://pdf4pro.com/cdn/service-bulletin-mckenzie-tank-lines-7fe6.pdf