Spicer Driveline Installation Service Manual - Manual (Page 6)

3
Installation Techniques
Common Causes of Vibrations
The three most common causes of driveshaft vibration are: Driveshaft Imbalance, Critical Speed, and Universal Joint Operating
Angles.
Driveshaft Imbalance
Eliminate the potential for balance problems before you undertake any other measures.
A driveshaft on a vehicle usually rotates at a higher rate of speed than the tire. For that reason, like tires, driveshafts should be
balanced.
Any time you build or rework a driveshaft, make sure it is dynamically balanced at, 3000 RPM for Light Duty or 2500 RPM for
Heavy Duty, to the following specifications:
Critical Speed
Every driveshaft has a critical speed. Critical speed is the point at which a rotating driveshaft begins to bow off its normal rotating
centerline.
Driveshafts begin to vibrate as they approach critical speed. If they are operated at near critical speed for an extended period, they
often fail. This can damage the vehicle and possibly injure persons nearby.
As a driveshaft fabricator or installer, you are responsible for checking the safe operating speed of any driveshaft you fabricate or
specify into an application. Make sure it will not operate at a speed higher than Spicer’s recommended safe operating speed. Use
Spicer Calculator (P/N J 3253) to determine safe operating speed.
Checking for a Possible Critical Speed Problem
Here is what you must do to make sure you won’t have a critical speed problem:
• Determine the safe operating speed of the driveshaft you want to use in your application. Insert the tube diameter and
center-to-center installed length of the shaft you want to use into a Spicer Safe Operating Speed Calculator (P/N. J3253).
The calculator will tell you the safe operating speed of the shaft you have chosen.
• Determine the NORMAL and MAXIMUM POSSIBLE operating speed of the driveshaft.
REMEMBER:
• On vehicles with a standard transmission that have a 1:1 direct drive high gear and no overdrive, MAXIMUM POS-
SIBLE driveshaft RPM is the same as the maximum possible ENGINE RPM.
• On vehicles that have an overdrive transmission, MAXIMUM POSSIBLE driveshaft RPM is higher than maximum
possible ENGINE RPM.
Series Specification
1310, 1330 .375 oz-in total at each end of shaft *
1350, 1410 .500 oz-in total at each end of shaft *
1480 - 1880 1.00 oz-in for each ten pounds of driveshaft weight divided proportionally at each end of shaft
* Passenger Car, Light Truck, Van, and SUV only. Industrial, Mobile Off-Highway, PTO, etc. same as 1480 - 1880.