Drive Line Alignment

 

by John Stanford

 When building your project car you want to make sure that your driveline (engine, transmission, driveshaft and rearend) is properly aligned.  This will help eliminate “premature destruction” of your transmission, universal joints and your rearend. 

There are two methods or schools of thought on this subject.  

"Un-cancelled Working Angle" and "4 degree parallel"


The first method deals with the drive line “un-cancelled working angle”.

This is the one I personally use and it is also relatively easy to follow.

 The objective here is to obtain a drive line “un-cancelled working angle” of zero (0°) degrees. 

An un-cancelled working angle other than zero (0°) degrees can cause drive line vibration resulting in damage to your u-joints, transmission seals and internal parts and can even cause “gear whine” and eventual destruction to a rearend.

  The formula is:  C = (A) – (B)

  A = (Engine set-up angle)  + (Driveshaft working angle)

  B = (Rearend set up angle) + (Driveshaft working angle)

  C = Un-Canceled working angle

Using an angle finder, obtain the working degrees of three components (1) engine, (2) driveshaft and  (3) the rearend. (Note: I use a “Craftsman Angle Finder” which can be obtained from your local Sears store or maybe borrowed from a friend or neighbor who has one).

If you come up with anything  other than “0°”, you will need  to change the angle of your engine, rearend or both.

 The engine degrees can be changed by placing shims or washers under the transmission mounting pad and the cross member it mounts on.  (Note: Remember to always set the engine so that the base of the carburetor (or the carburetor mounting surface on the intake manifold) is level at zero (0°) degrees.

 You can change the angle of the rearend by using “angle shims “ between the spring pad and the spring.

 The angle shims can be obtained in “1 degree” increments hence 1°,2°,3°,4° etc. from your local auto parts store or a drive line repair shop.

 

EXAMPLE:

 

 

  The formula is:  C = (A) – (B)

  A = (Engine set-up angle)  + (Driveshaft working angle)

  A = (           3                    )  + (               2                       )

  A = (5)

 

  B = (Rearend set up angle) + (Driveshaft working angle)

  B= (           3                    )  + (               2                       )

  B = (5)

 

  C = (A) – (B)

  C = (5) – (5)

  C = 0

 

 

 


  The second method goes like this.  

 Keep the vertical and horizontal centerlines of the transmission shaft and the pinion gear shaft within four degrees of the centerline of the drive shaft.

This method is recommended and used  by Tex Racing Enterprises Inc. located in Ether, NC.

John Ritter of Tex Racing Enterprises, Inc. states that "One way to prevent driveshaft vibration is to insure that the centerline from the crankshaft / transmission output shaft is within 4 degrees of being parallel to the pinion angle of the rearend under load.  If these two angles are not within 4 degrees, the critical speed will be decreased and vibration at highway speeds may be induced".

John also points out that every driveshaft has a certain speed, or rpm limit, called a driveshafts critical speed. At critial speed, the driveshaft will tend to vibrate and eventually destroy itself.  The idea is to decrease mass while increasing strength so that the driveshaft rpm will never reach the shafts critical speed.  Shortening the driveshaft, increasing its diameter and changing to aluminum are the quickest ways to boost critical speed.

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