Drive Shaft Alignment GMC Cab & Chassis R2500

DESCRIPTION

Drive shafts are balanced, one-piece, tubular shafts with universal joints at each end. Number used in vehicle varies: one shaft, 2 shafts with a center bearing, or 3 shafts. Three shafts are used in many 4WD applications. Location of slip joints varies with model and manufacturer. (Scheme 3)

View of 5 Commonly Used Drive Shaft Combinations Many 4WD models use 3 drive shafts. Scheme 3

INSPECTION

Vibration can come from many sources. Before overhauling driveline, other sources of possible vibration should be checked first.

TIRES & WHEELS

Check tire inflation and wheel balance. Check for foreign objects in tread, damaged tread, mismatched tread patterns or incorrect tire size.

CENTER BEARING

Tighten drive shaft center bearing mounting bolts. If bearing insulator is deteriorated or oil-soaked, replace it.

ENGINE & TRANSMISSION MOUNTINGS

Tighten mounting bolts. If mountings are deteriorated, replace them.

Check drive shaft for damage or dents that could affect balance. Check for undercoating adhering to shafts. If present, clean shafts thoroughly.

UNIVERSAL JOINTS

Check for foreign material stuck in joints. Check for loose bolts and worn bearings.

2-Piece Shafts

1. All General Motors models with 32 splines use keys on spline and slip joint, which can only mate in correct position. On most models with 2-piece shafts, proper phasing is accomplished by keys on spline and slip joint.
2. On models with 2-piece shafts, rotate transmission yoke until trunnion is in horizontal plane. Install front drive shaft with "U" joint trunnion in vertical plane. Connect bearing support to crossmember.
3. Ensure that front face of bearing support is perpendicular (90 degrees) to centerline of drive shaft. Install rear drive shaft with "U" joint trunnion of slip joint in vertical plane.
4. Set differential pinion yoke trunnion in vertical plane. Connect rear drive shaft to pinion yoke. If 2-piece shaft is correctly installed, centerline of trunnions at each end of individual shafts will be parallel. (Scheme 4)

Phase Alignment Of 2-Piece Drive Shafts Trunnion yoke ears on each shaft must be parallel. Scheme 4

One-Piece Shafts

Check that flanges on either end of drive shaft are in same plane. Often there are arrows on slip joint and drive shaft to aid in alignment. (Scheme 5) If flanges are not in same plane, disassemble universal joint and align.

Slip Joint Alignment Arrows Align arrows for proper shaft phasing. Scheme 5

DRIVE SHAFT BALANCE

1. Drive shaft imbalance may often be cured by disconnecting shaft and rotating it 180 degrees in relation to other components. Test by raising rear wheels off ground, and turning shaft with engine. NOTE: DO NOT run engine with transmission engaged for prolonged periods, as overheating of engine or transmission may occur.
2. On most models, balancing may be done by marking shaft in 4 positions, 90 degrees apart. Place marks approximately 6" forward of weld, at rear end of shaft. Number marks one through 4.
3. Place screw-type hose clamp in number one position, and rotate shaft with engine. If there is little or no change, move clamp to No. 2 position, and repeat test.
4. Continue procedure until vibration is at lowest level. If no difference is noted with clamp moved to all 4 positions, vibrations may not be drive shaft imbalance.
5. If vibration is lessened but not completely gone, place 2 clamps at that point, and run test again. Combined weight of clamps in one position may increase vibration. If so, rotate clamps 1/2" apart, above and below best position, and repeat test.
6. Continue to rotate clamps as necessary, until vibration is at lowest point. When point is reached where vibration has been eliminated, bend end of clamp so it will not loosen. If vibration level is still unacceptable, repeat procedure at front end of drive shaft.

Drive Shaft Phase Alignment Align drive shaft and slip joint trunnions in same plane. Scheme 6

Scheme 7

Scheme 8

Scheme 9

Scheme 10

Scheme 11

1. All flanges must be perpendicular in both vertical and horizontal planes to engine crankshaft. Only exception is "broken back" type driveline, which has flanges that are not perpendicular in vertical plane. (Scheme 7) (Scheme 7): Typical "Broken Back" Type Drive Shaft Alignment Angle "A" equals angle "B".
2. With nonparallel or "broken back" type installation, working angles of universal joints of given drive shaft are equal. Angle "A" = angle "B".
3. This is calculated as follows: angle of output shaft centerline is subtracted from angle of drive shaft. Difference should equal angle of drive shaft subtracted from pinion shaft angle.
4. Parallel type joints maintain constant velocity between output shaft and pinion shaft. Vibration is minimized and component life maximized when universal joints are parallel. (Scheme 8): Aligning One-Piece Drive Shaft Yokes must be parallel.
5. Using dial indicator, measure runout of transmission flange, center bearing flange and pinion flange. If runout exceeds.003-.005" (.08-.13 mm), replace flange.
6. If dial indicator cannot be used, push rod with slip fit through flange bearing bore. See if it aligns with opposite bore. If not, replace flange.
7. Rotate transmission flange until it is vertical, measuring from side. Check center bearing and pinion flanges. They cannot be more than one degree off vertical. See «DRIVE SHAFT PHASING»(/gmc/cab-chassis-r2500/1987-1987/remont/driveshaft-universal-joints/#drive-shaft-alignment) in this article. (Scheme 9): Vertical Alignment of Drive Shaft Flanges in pairs should be parallel.
8. Rotate transmission flange until it is vertical, measured from side. Measure angle from end and record it. Check all other flanges for same angle. They must be within 1/2 degree of each other. Adjust as required.
9. If difficulty is encountered when making above adjustments, horizontal alignment should be checked. Even though vertical alignment is correct, horizontal alignment can be badly out of adjustment. This is often found after major component replacement or repair of serious accident damage. (Scheme 10) (Scheme 10): Horizontal Alignment of Drive Shaft Plane of trunnions should be parallel.
10. To make horizontal alignment checks, set straightedges up. (Scheme 11) Set transmission output flange horizontal and clamp straightedge to flange in a horizontal plane. Repeat procedure with drive pinion flange. Ensure that flanges are horizontal by checking angle of straightedge with spirit level. (Scheme 11): Checking Horizontal Alignment Measure at 6 points shown using straightedges and framing squares.
11. Using straightedge that is 12" longer than width of rear wheel track at 90 degrees, clamp to frame side rails. Use large framing squares to align straightedge with side rails.
12. Measure distance "X" at each side. If both measurements are not within 1/16" (1.6 mm) of each other, transmission flange is horizontally misaligned.
13. Measure distance "Y" (edge of straightedge to axle shaft centerline) at each side. If 2 dimensions are not within 1/8" (3.2 mm) of each other, axle housing is misaligned.
14. Measure distance "W" at each side. If both measurements are not within 1/16" (1.6 mm) of each other, pinion flange is horizontally misaligned.

See also:
• DRIVE SHAFT PHASING