4905 Vibrations

[Rick Brown]

My 4905 has a vibration between 30 and 50 mph when the engine is loaded (power or jakes).  The last time I had a vibration it was the pumpkin going out.  I was only a $880 tow job away from home when the cause revealed itself.  Now I feel the need for a better diagnosis tool than obvious failure.  How do people who know what they are doing diagnose on the road vibrations?
Thanks for any comments.
-Rick Brown in Reno, NV

[TomC]

Depends on the type of vibration. Is it a low frequency vibration that corelates with the tire revolutions-then an out of balance tire.  Is it a vibration that get faster with the speed of the bus without regard to the engine speed-then axle gears or a U joint going out or out of balance drive shaft.  Does the vibration corelate with the engine speed-then out of balance something on the engine-usually the flywheel.  Give us an idea what the vibration is like.  Good Luck, TomC

[captain ron]

I had a similar problem with my old 4905 and it was a loose bolt back on the bulkhead that was part of (if I remember correctly) the motor or transmission mount. Also the second day I had it it started vibrating bad and a bad u joint caused the drive shaft to come loose from the differential and the drive shaft got bound up and broke the tranny in half, yes in half. so check those two items.