For 4WD Trucks, remove the rear propeller shaft, seal output shaft and drive the vehicle in 4WD. If the vibration is gone, the rear prop shaft
could be the problem.

•

For vehicles with a 3:08 with a one-piece steel shaft, this can be replaced with a one-piece aluminum one that is utilized on all 3:42 and 3:73
ratios (K15543 and K15753 Models only).

8

•

PIP5140: Low Speed Vibration 30-35 mph (48-56 km/h).

•

Inspect the transmission output shaft bushing for irregular wear.

Condition 3: 2nd Order Prop Shaft (Normally a launch shudder or left under hard acceleration)
Note: Vehicle rear suspension must be properly supported during the Driveline Angle measurement process in order to record true Driveline Angle
measurements.

Check Driveline Angles (Refer to SI Document ID# 2084724)
Suggestion:
1.

Check Angle.

2.

Disassembly/reassembly rear yoke – check for shift in U-joint.

3.

Check Angle.

4.

Evaluation Drive.
Measurement

Notes:

Yoke to Shaft

The first (forward most) U-joint action on a two piece
driveshaft system is not canceled out by another Ujoint. Because of this, the first U-joint working angle
should be between 0. 5 and 0.75 degrees.

Front Shaft to Center Support
Bearing (if equip)

U-joint pairs cancel each other. Neither U-joint
working angle should exceed 4 degrees, nor the
allowable range of difference between cancelling Ujoint working angles is 0.00 to 1.0 degrees.

Shaft to Diff Yoke

Propeller systems containing only 1 U-joint: The U-joint working angle should be between 1/2 and 3/4 degrees.
Allowable range of difference between cancelling U-joint working angles: 0.25 to 1.0 degrees.

Shimming
Important: This is only be used for trucks that have incorrect working angles.

Options:
1.

Trucks were built prior to 1/1/2015 had a 14 mm spacers under the transfer case (4WD only). Starting with 1/1/2015. The shim was reduce
to 7 mm shim which may correct the condition.

2.

A 2 degree axle shim (P/N 23469809 – Qty 2) can be placed between the leaf spring pack and the axle perch. To rotate the pinion up to
correct this; the “fat end” of the shim must face backwards, to the rear of the truck.

Center Support Bearing - Two Piece Propeller Only
Change center support bearing shim from 12 mm (0.47 in) to 6 mm (0.24 in) using washers or other means. (If replacing the propeller, the new one
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will come with 6 mm or 0.24 in shim).

Condition 4: 3rd Order Tire with 1st Order Prop

•

3rd Order Tire combined with 1st Order Prop. This type will create a phasing boom. Need to focus on the 1st Order Prop – condition above.

Condition 5: Vibration Felt in 4 Cyl Mode (AFM) – V6 Engine Only
Several customers have commented on a vibration felt in the steering wheel or seat during 4 Cylinder Active Fuel Management (AFM) operation. This
can be noticed more at 64-72 km/h (40-45 mph) and by lightly accelerating to the point where the engine transitions to 6 cylinders, or V6 mode.

•

This type of vibration can be the result of exhaust cross pipe ground out and/or cab mount ground out.

To repair this condition, the three-way catalytic converter settling procedure in PIP5228: Vibration During Active Fuel Management V4 Mode
Operation 1200–1400 Engine RPM should be completed.

Condition 6: Vibration Felt at Idle Only

•

Refer to the PIP5137: Rough Idle or Vibration In Drive.

Other Sources of Vibrations
1.

Exhaust resonance – PI1201: Exhaust Rattle, Buzz, Pop or Whistle.

2.

Vibration during active fuel management V4 mode operation – PIP5228. Follow this cab mount settling procedure listed below:
Warning: When settling the body cushions, do NOT separate the frame from the body more than is necessary. Possible personal
injury and damage to multiple parts may result if you do not follow the guides outlined below:

•
•
•
•
•

Intermediate steering shaft – Do not allow the shaft to extend more than 25 mm (1 in).
Fuel tank filler hose – Do not stretch the hose excessively.
Tail/Turn signal lamp wiring/rear lamps junction block – Leave slack in the wires
Park brake cable – Leave slack in the cable
Body ground straps – Leave slack in the wire
⇒

The technician should first loosen the fastener located at the center of each body mount (6 for a regular cab, 8 for crew and double
cab).

⇒

Using a large angled pry bar, lift up the cab body slightly to settle / relax it. Perform this at each mount location one at a time.

⇒

Repeat this cab mount settling process twice, to confirm the mounts are settled / relaxed.
Visually verify that the cab to box alignment is correct before re-torquing all mounts to specification found in Service Information,
body repair, frame and under body section.
The cab / body mount position location
The numbers in the picture below indicate the specific mount position. The mounts on the passenger side of the vehicle are
identified the same way. This will assist the technician to identify the correct location of each mount so they can be torque to the
proper specification.

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1 = body mount cushion front
2 = body mount cushion position number 1
3 = body mount cushion position number 2
4 = body mount cushion position number 3
Pitchline runout – Pitchline runout will normally show as a 1st order tire vibration on the PicoScope. If after correcting tire(s) with excessive
Road Force, a vibration exists, remove differential cover and check ring gear backlash. Every tooth should be checked for excessive

3.

backlash. If there is more than 0.0762 mm (0.003 in) of variation, the ring gear and/or differential should be replaced to correct the condition
(SI Document ID# 3269088, 3620298) (PIP4148).

Backlash Adjustment Procedure
Special Tools:

•

J-8001 Dial Indicator Set

•

J-25025 Guide Pins

Note:

•

Ensure that the side bearing surfaces in the axle housing are clean and free of burrs. If the original bearings are to be reused, the original
bearing cups must also be used.

•

The differential side bearings must be initially preloaded in order to determine the backlash of the gear set. After the backlash is set, the final
bearing preload is set.

•

Mark the bearing caps left or right sides.

1.

Measure the rotating torque of the drive pinion and differential assembly. Refer to the Differential Drive Pinion Gear Bearing Replacement in
SI.

11

2.

Install the J-25025 pins and the J-8001 indicator to the axle housing.
Note: Preload the dial of the J-8001-3 indicator approximately ¾ of a turn and zero the gauge.

Note: The illustration above is for reference only. The differential does NOT need to be removed from the vehicle.
3.

Set the J-8001-3 indicator (1) so that the stem is aligned with the gear rotation (1) and square to the tooth angle.

4.

Hold the drive pinion stationary and move the ring gear back and forth.

5.

Repeat the measuring procedure at each tooth around the ring gear.

6.

The difference between the backlash at all of the measuring points should not vary by more than 0.05 mm (0.002 in).

7.

If the difference between the backlash at all of the measuring points varies by more than 0.05 mm (0.002 in), inspect for burrs, a distorted
case flange or uneven bolting.

8.

If the difference between all the measuring points is within specifications, the backlash at the minimum lash point measured should be 0.080.25 mm (0.003-0.010 in) with a preferred backlash of 0.13-0.18 mm (0.005-0.007 in).
Note:

•

Increasing or decreasing the shim thickness by 0.05 mm (0.002 in) will change the backlash adjustment approximately 0.03 mm
(0.001 in).

•

If the backlash is less than, select a smaller shim than the one that was removed. For example, to INCREASE the backlash by 0.05 mm
(0.002 in), select a shim that is 0.10 mm (0.004 in) thinner than the shim that was removed.

•

If the backlash is larger than, select a larger shim than the one that was removed. For example, to DECREASE the backlash by
0.05 mm (0.002 in), select a shim that is 0.10 mm (0.004 in) thicker than the shim that was removed.

9.

Install the selected shim.
Caution: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Do
not use paints, lubricants, or corrosion inhibitors on fasteners, or fastener joint surfaces, unless specified. These coatings affect fastener
torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing
12

fasteners in order to avoid damage to parts and systems. When using fasteners that are threaded directly into plastic, use extreme care not
to strip the mating plastic part(s). Use hand tools only, and do not use any kind of impact or power tools. Fastener should be hand tightened,
fully seated, and not stripped.
10. If the backlash is to small, increase the backlash using the following procedure:
10.1. Remove the bearing cap bolts and the bearing caps.
Note: Mark the bearing cups and the shims left or right.
10.2. Remove the differential case assembly with the bearing cups and the shims.
Note: Measure the production shim or the shim and service spacer in 3 locations.
Measure each shim separately.
10.3. Measure the thickness of left side shim pack.
Note: If the original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to
increase the backlash by 0.05 mm (0.002 in), remove 0.10 mm (0.004 in) in of thickness from the left side shim pack.
10.4. Calculate the average of the 3 measurements for each shim.
Note: If the original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to
increase the backlash by 0.05 mm (0.002 in), remove 0.10 mm (0.004 in) of thickness from the left side shim pack.
10.5. Assemble a new left side shim pack by decreasing the appropriate amount of thickness from the original left side shim pack.
Note: Measure each shim separately.
10.6. Measure the thickness of right side shim or the shim and service spacer in 3 locations.
Note: Add the average of each of the shim measurements together. Record the measurement. This is the thickness for the right side shim
pack.
10.7. Calculate the average of the 3 measurements for each shim.
10.8. Assemble a new right side shim pack by increasing the appropriate amount of thickness to the original right side shim pack. If the
original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to
increase the backlash by 0.05 mm (0.002 in), add 0.10 mm (0.004 in) of thickness to the right side shim pack.
11. Use the following procedure to decrease the backlash if the backlash is too large:
11.1. Remove the bearing cap bolts and the bearing caps.
Note: Mark the bearing cups and the shims left or right.
11.2. Remove the differential case assembly with the bearing cups and the shims.
Note: Measure the production shim or the shim and service spacer in 3 locations. Measure each shim separately.
11.3. Measure the thickness of left side shim pack.
Note: Add the average of each of the shim measurements together. Record the measurement. This is the thickness for the left side shim
pack.
11.4. Calculate the average of the 3 measurements for each shim.
11.5. Assemble a new left side shim pack by increasing the appropriate amount of thickness to the original left side shim pack. If the
original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to
increase the backlash by 0.05 mm (0.002 in), add 0.10 mm (0.004 in) of thickness to the left side shim pack.
Note: Measure the shim or the shim and service spacer in 3 locations. Measure each shim separately.
11.6. Measure the thickness of right side shim pack.
Note: Add the average of each of the shim measurements together. Record the measurement. This is the thickness for the right side shim
pack.
11.7. Calculate the average of the 3 measurements for each shim.
11.8. Assemble a new right side shim pack by decreasing the appropriate amount of thickness to the original right side shim pack. If the
original shim is cast iron production shim, assemble the shim pack using a service spacer and service shims. For example, to
decrease the backlash by 0.05 mm (0.002 in), remove 0.10 mm (0.004 in) of thickness to the right side shim pack.
12. Install the differential case assembly with the bearing cups.
13. Install the left side service shims between the axle housing and the differential case.
14. Install the right side service shims between the axle housing and the differential case.

13

Note: The service spacers must be installed between the service shim(s) and the axle housing.
15. Using the brass drift for 9.5/9.76 axle, install the left side service spacer.
16. Recheck the backlash and adjust, if necessary.
17. Install the bearing caps and bolts and tighten to 85

Y

(63 lb ft).

18. Recheck the backlash and adjust, if necessary.
19. Once backlash is correct, perform a gear tooth contact pattern check in order to ensure proper alignment between the ring and pinion gears.
Refer to the Gear Tooth Contact Pattern Inspection in SI.
Note: Recheck the backlash following the steps above to verify that the backlash is within specifications.
20. Tighten the differential bearing cap bolts to 85

Y

(63 lb ft).

21. Measure the drive pinion and differential case side bearing preload and adjust, if necessary following the steps above.
22. Once the backlash and bearing preload is correct, perform a gear tooth contact pattern check in order to ensure proper alignment between
the ring and pinion gears. Refer to the Gear Tooth Contact Pattern Inspection in SI.
Once all areas of vibrations has been reduced, if there is still vibration that the customer is concerned about, the following diagnosis
maybe helpful to determine if a shock issue exists.
Warning: The following items should NOT be utilized until the source of the problem has been corrected.

Potential Vibration/Rough Ride:
Condition/Concern
The shock issues below DO NOT cause a vibration, it will only make an existing vibration feel worse. In some cases, a vibration that would not
normally be a customer concern may now be felt due to a bad shock. But in general, the original source of the vibration, whether it is the wheels,
tires, propeller shaft, etc, will have to be corrected. When diagnosing a vibration issue, there have been reports of the shocks amplifying the vibration
felt inside the truck. Engineering has found that some shocks may have been built with contaminated shock oil. This may cause the shocks to
dampen incorrectly.

This only applies to the following shocks:

•

Rear- Only trucks listed with the Z71 option (RPO Z71, these shocks will be white in color)

Recommendation/Instructions:
Two checks are needed to be performed to verify if the shocks could be an issue:
1.

Check the date code located on the bottom of the shock. The first 8 digits are the GM part number. The next 5 digits are the supplier part
number. The last 5 digits will be the date code. Any shock built before A1474 could have an issue. The date code format is as follows: 1st
digit is the plant, next 3 digits are the day of the year and the last digit is the last number of the year.

Example:
–

A14743C

–

A = Plant

–

147 = 147th Day of the Year

–

4 = 2014
14

–
2.

3C = Drawing Change Level

If the rear shocks are built before this date code, they will have to be removed for a dynamic test.

Dynamic Test (Rear Shock – Z71 option only)
Starting with a fully extended shock, compress the rod taking notice of the first 10 millimeters of travel. A good shock will not have any free play and
there will be immediate resistance to being compressed. A shock with an issue will have several millimeters of free play (no resistance) before
feeling the resistance from being compressed. Replace any shocks with excessive free play. In most cases, the rear shocks will be the issue.

Warranty Information
For vehicles repaired under the Bumper-to-Bumper coverage (Canada Base Warranty coverage), use the following labor operation. Reference the
Applicable Warranties section of Investigate Vehicle History (IVH) for coverage information.
Labor Operation

Description

Labor Time

3080138*

Perform Pico Scope Vibration Measurement and Road Test

0.5 hr

8080108*

Perform Road Force Measurement

0.9 hr

Add time to vector each tire correction (Before and after Road force number
should be noted on Vibration worksheet)

0.2 hr

3080088*

Perform Prop Shaft Measurement and Balance (two hose clamp method)

0.8 hr

8033641

Front Shock Absorber, Shock Absorber Component, or Spring Replacement Both Sides

1.2 hrs

8044751

Rear Shock Absorber Replacement - Both Sides

0.7 hr

3080168*

Steering Gear Support Bushing Replacement

3.0 hrs

1431160

Body Mount Upper and Lower Cushion Replacement

1.2 hrs

Note: For steering wheel angle and/or front toe adjustment times, refer to labor code 8070012 and add the applicable base times to base labor
hours.
**

Replace Tire(s)

*This is a unique Labor Operation for Bulletin use only.
**Use the appropriate labor operation code in SI specific to the manufacturer of the tire being replaced.

Vibration Diagnostic Worksheet
Vibration Felt In:
Seat:

Steering Wheel:

Other:

Complaint Speed:

VIN:

Year:

Model:

Symptom:
Engine:

Engine Speed:

15

Use Published Labor
Operation Time

Tire Brand:

Tire Size:

Axle Ratio:

Gear:

TPC Spec:
Primary
Frequency:

Type (circle): T1 T2 T3 E1 E4 P1 P2
Other:
Measurement of vibration is M/g’s (# of runs? Peak, Average, and Avg of Peaks?)
________________________________________________________________________________
Source of Vibration (Based PICO)
________________________________________________________________________________
Secondary

Frequency:

Type (circle): T1 T2 T3 E1 E4 P1 P2
Other:
Measurement of vibration is M/g’s (# of runs? Peak, Average, and Avg of Peaks?)
________________________________________________________________________________
Source of Vibration (Based PICO)
________________________________________________________________________________

Condition 1: Road-Force Measurements
Before Repairs
Ounces

Road Force (Lbs)

Right Front
Left Front
Right Rear
Left Rear
After Repairs
Ounces

Road Force (Lbs)

Right Front
Left Front
Right Rear

16

Left Rear

GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer". They are written to inform these technicians of conditions
that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the
equipment, tools, safety instructions, and know-how to do a job properly and safely. If a condition is described, DO NOT assume that the bulletin
applies to your vehicle, or that your vehicle will have that condition. See your GM dealer for information on whether your vehicle may benefit from the
information.

WE SUPPORT VOLUNTARY TECHNICIAN CERTIFICATION

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