Rear end is crooked after shackle/hanger install
04-09-2007, 09:17 AM
#11
TECH Junkie
Join Date: Jul 2005
Location: Lake Conroe Texas
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You've got chevy lean and yes, you had it before you dropped it. It's not noticeable when you've got a 6" gap between the tire and fender, but when you shorten that gap, the difference becomes obvious. Most guys don't notice until installing drop shackles - like me.
Here's a couple of GM tech bulletins with part numbers for spacers:
Here's a couple of GM tech bulletins with part numbers for spacers:
Subject: Left Front of Vehicle Sits Low - keywords alignment appearance body fender spring suspension #PIT3281A - (12/13/2005)
Models: 1999-2006 Chevrolet Silverado
1999-2006 GMC Sierra
2 Wheel Drive Models Only
--------------------------------------------------------------------------------
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Left front of vehicle sits low.
Recommendation/Instructions:
Measure front trim height keeping in mind that the trim height tolerance is .5" difference side to side. Verify that the vehicle is equipped with the correct production front springs. You should measure the standing height of both front springs to ensure that they are equal height. Check "z" height measurements as per SI. After determining that the above checks do not influence the concern, install a front spring upper insulator, P/N 15756770 in the lower control arm spring pocket. Install 1 insulator at a time and measure the change between installations. A maximum of 2 insulators per spring pocket may be used.
Please Note: The steering alignment and headlight aim must be checked if the vehicle ride height was changed.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
Models: 1999-2006 Chevrolet Silverado
1999-2006 GMC Sierra
2 Wheel Drive Models Only
--------------------------------------------------------------------------------
The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.
Condition/Concern:
Left front of vehicle sits low.
Recommendation/Instructions:
Measure front trim height keeping in mind that the trim height tolerance is .5" difference side to side. Verify that the vehicle is equipped with the correct production front springs. You should measure the standing height of both front springs to ensure that they are equal height. Check "z" height measurements as per SI. After determining that the above checks do not influence the concern, install a front spring upper insulator, P/N 15756770 in the lower control arm spring pocket. Install 1 insulator at a time and measure the change between installations. A maximum of 2 insulators per spring pocket may be used.
Please Note: The steering alignment and headlight aim must be checked if the vehicle ride height was changed.
Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.
Subject: Vehicle Lean - Left Front Sits Low or Right Rear High (Add Spacer Between Left Rear Spring Pack and Axle) #06-03-06-005 - (09/19/2006)
Models: 1999-2007 Chevrolet Silverado (Classic)
1999-2007 GMC Sierra (Classic)
with Two-Wheel Drive
--------------------------------------------------------------------------------
ConditionSome customers may comment that their vehicle appears to lean. In most cases, the vehicle will sit low left front or high right rear.
Correction
Measure fender wheel-opening heights, front and rear, to quantify vehicle lean. Fender wheel-opening heights are related to, but distinct from, trim height (a.k.a. Z and D height). The front wheel-opening height is known as P height, and the rear wheel-opening height is know as R height. The P and R heights are not set at the factory, nor is a specification given for them. However, they are the most direct and repeatable measurement of what a customer would see as the vehicle leaning. Perform the following before measuring the fender wheel-opening heights:
• Make sure the vehicle is on a level surface, such as an alignment rack.
• Set the tire pressures to the pressure shown on the certification label. Refer to Label - Vehicle Certification in General Information.
• Check the fuel level. Add additional weight if necessary to simulate a full tank.
• To ensure proper weight distribution, make sure the rear storage compartment is empty.
• Close the doors and hood.
P Height and R Height Measurements
P height and R height are measured the same way. They are the distance from the ground to the highest point on their respective wheel-opening, going through the center of their respective wheel. Record the measurement on the repair order.
If the difference fromleft to right for P and R height is 15 mm (0.59 in) or less, no repairs are suggested as the vehicle is within specification. If the difference exceeds 15 mm (0.59 in) for either measurement, install the spring spacer to the left rear side of the vehicle following the procedure below.
Raise and support the vehicle.
Support the rear axle.
Remove the U-bolt nuts, remove the U-bolts and anchor plate. Discard the U-bolts. DO NOT discard the nuts or anchor plate.
Remove the lower shock nut and bolt.
Raise the vehicle or lower the axle enough to allow for installation of the spacer. Install the spacer, P/N 15872657.
Lower the vehicle or raise the axle.
Install the lower shock nut and bolt.
Tighten
Tighten to 95 N·m (70 lb ft).
Install the anchor plate, new longer U-bolts, P/N 15872655, and nuts.
Tighten
Tighten the nuts to 72 N·m (53 lb ft).
Remove the axle support and lower the vehicle.
Re-check the P and R heights in the previous location. Record these readings on the repair order.
After all measurements are done, perform a road test and check headlight aim.
If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
Parts Information
Part Number
Description
Qty
15872655
Rear Spring Spacer
1
15872657
Rear Spring U-Bolt
2
Models: 1999-2007 Chevrolet Silverado (Classic)
1999-2007 GMC Sierra (Classic)
with Two-Wheel Drive
--------------------------------------------------------------------------------
ConditionSome customers may comment that their vehicle appears to lean. In most cases, the vehicle will sit low left front or high right rear.
Correction
Measure fender wheel-opening heights, front and rear, to quantify vehicle lean. Fender wheel-opening heights are related to, but distinct from, trim height (a.k.a. Z and D height). The front wheel-opening height is known as P height, and the rear wheel-opening height is know as R height. The P and R heights are not set at the factory, nor is a specification given for them. However, they are the most direct and repeatable measurement of what a customer would see as the vehicle leaning. Perform the following before measuring the fender wheel-opening heights:
• Make sure the vehicle is on a level surface, such as an alignment rack.
• Set the tire pressures to the pressure shown on the certification label. Refer to Label - Vehicle Certification in General Information.
• Check the fuel level. Add additional weight if necessary to simulate a full tank.
• To ensure proper weight distribution, make sure the rear storage compartment is empty.
• Close the doors and hood.
P Height and R Height Measurements
P height and R height are measured the same way. They are the distance from the ground to the highest point on their respective wheel-opening, going through the center of their respective wheel. Record the measurement on the repair order.
If the difference fromleft to right for P and R height is 15 mm (0.59 in) or less, no repairs are suggested as the vehicle is within specification. If the difference exceeds 15 mm (0.59 in) for either measurement, install the spring spacer to the left rear side of the vehicle following the procedure below.
Raise and support the vehicle.
Support the rear axle.
Remove the U-bolt nuts, remove the U-bolts and anchor plate. Discard the U-bolts. DO NOT discard the nuts or anchor plate.
Remove the lower shock nut and bolt.
Raise the vehicle or lower the axle enough to allow for installation of the spacer. Install the spacer, P/N 15872657.
Lower the vehicle or raise the axle.
Install the lower shock nut and bolt.
Tighten
Tighten to 95 N·m (70 lb ft).
Install the anchor plate, new longer U-bolts, P/N 15872655, and nuts.
Tighten
Tighten the nuts to 72 N·m (53 lb ft).
Remove the axle support and lower the vehicle.
Re-check the P and R heights in the previous location. Record these readings on the repair order.
After all measurements are done, perform a road test and check headlight aim.
If these steps do not resolve the condition, please contact GM TAC for further diagnostic assistance.
Parts Information
Part Number
Description
Qty
15872655
Rear Spring Spacer
1
15872657
Rear Spring U-Bolt
2
04-09-2007, 08:45 PM
#13
TECH Apprentice
Join Date: Feb 2007
Location: Houston, Tx.
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chevy lean !!!!!!!!! i have that on my truck too and its sitting at stock height.
i think every GM truck has that, it just more noticeable on some than it is on others.
i think every GM truck has that, it just more noticeable on some than it is on others.
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