Frame & Underbody Cadillac STS I

Fastener Tightening Specifications

Fastener Tightening Specifications

Underbody Inspection

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/sts/i-2004-2007/remont/hoistjack/#general-information) in General Information.
2. Check for obvious deterioration of the floor pan.
3. Check for loose dirt and corrosion around the inside of the floor pan reinforcement member access holes. This is the first indication that corrosion may exist in hidden areas, and repairs may be required before the final cleaning and protective treatment is performed.
4. Using a chisel, ensure that the drain provisions in the floor pan reinforcement members are open. There are drain holes in the body side panels also. These holes can be opened using a punch or a drift. The side panel drain holes are in the rear section of the rocker panels, and in the lower rear quarter panels.

Frame Replacement - Front

Tools Required

1. J 24319-B Steering Linkage and Tie Rod Puller. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .
2. J 39580 Engine Support Stand. See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .

Removal Procedure

1. Install the engine support fixture. Refer to the following procedures: «Engine Support Fixture»(/cadillac/sts/i-2004-2007/remont/mechanical/#engine-mechanical-36l-ly7-2-of-6__engine-support-fixture) in Engine Mechanical - 3.6L (LY7) «Engine Support Fixture»(/cadillac/sts/i-2004-2007/remont/mechanical/#engine-mechanical-46l-lh2-2-of-6) in Engine Mechanical - 4.6L (LH2)
2. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/sts/i-2004-2007/remont/hoistjack/#general-information) in General Information.
3. Remove the front wheels. Refer to «Tire and Wheel Removal and Installation»(/cadillac/sts/i-2004-2007/remont/wheel-tire-system/#tires-and-wheels) in Tires and Wheels.
4. Remove the front air deflector. Refer to «Air Deflector Replacement - Front»(/cadillac/sts/i-2004-2007/remont/exterior-body-panels/#body-front-end) in Body Front End.
5. Disconnect the electrical harness retainers (1) securing the engine harness to the frame.
6. Disconnect the left rearward retainer (1).
7. Disconnect the right rearward retainer (1).
8. Disconnect the antilock brake wiring harness from the lower control arms.
9. Loosen the brake line bracket nut (1).
10. Disconnect the brake lines from the frame.
11. Using mechanics wire (3), support the radiator and AC condenser assembly to the front inner energy absorber bracket bolt (1).
12. Remove the washer bottle bracket nuts and bracket (3).
13. Loosen the brake pressure modulator valve (BPMV) nuts (1) in order to separate the BPMV (2) from the bracket assembly.
14. Loosen the stabilizer shaft mounting bolts.
15. Remove the lower stabilizer shaft link retaining nut.
16. Remove the stabilizer shaft link from the lower control arm.
17. Remove the power steering pressure hose retaining nut from the air conditioning compressor.
18. Position power steering pressure hose aside.
19. Remove the power steering gear mounting bolts.
20. Using mechanics wire (4), support the power steering gear (3) to the bolt bracket installed in the oil pan.
21. Remove the outer tie rod retaining nut.
22. Using J 24319-B . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .
23. Remove the lower shock bolts (1).
24. Disconnect the lower ball joint from the steering knuckle and position the knuckle assembly away from the lower control arms. Refer to «Lower Control Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-front/#front-suspension-system) in Front Suspension.
25. Remove the engine mounts lower retaining nuts (2).
26. Install the J 39580 . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .
27. Lower the vehicle to the frame support table.
28. Remove the frame mounting bolts (2).
29. With the aid of an assistant, carefully raise the body from the frame.
30. Ensure when raising the body, the following items are clear from the frame: The brake pipes The steering knuckle assembly The wheel speed sensor (WSS) electrical harness
31. Remove the lower control arms. Refer to «Lower Control Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-front/#front-suspension-system) in Front Suspension.
32. Remove the stabilizer shaft. Refer to «Stabilizer Shaft Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-front/#front-suspension-system) in Front Suspension.
33. With the aid of an assistant, remove the frame from the support fixture.

Installation Procedure

1. Install the lower control arm to the frame. Refer to «Lower Control Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-front/#front-suspension-system) in Front Suspension.
2. Install the stabilizer shaft to the frame. Refer to «Stabilizer Shaft Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-front/#front-suspension-system) in Front Suspension. Do not tighten the stabilizer shaft mounting bolts at this time.
3. With the aid of an assistant, position and secure the new frame assembly to the support fixture.
4. With the aid of an assistant, carefully lower the body to the frame.
5. Ensure the following components are clear from the frame: The electrical harness The steering knuckle assembly The brake pipes
6. Install the frame mountings bolts (2). Tighten: Tighten the bolts to 191 N.m (141 lb ft).
7. Raise the vehicle.
8. Install the engine mount lower retaining nuts (2). Tighten: Tighten the nuts to 50 N.m (37 lb ft).
9. Remove the J 39580 . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .
10. Remove the mechanics wire (4) supporting the power steering gear (3).
11. Install the power steering gear mounting bolts. Tighten: Tighten the bolts to 95 N.m (70 lb ft).
12. Install the ball joint to the steering knuckle.
13. Install the lower ball joint retaining nut. Tighten: Tighten the nut to 20 N.m (15 lb ft) plus an additional 210 degree rotation.
14. Install the outer tie rod to the steering knuckle.
15. Install the outer tie rod to steering knuckle retaining nut. Tighten: Tighten the nut to 70 N.m (52 lb ft).
16. Tighten the stabilizer shaft bolts. Tighten: Tighten the bolts to 60 N.m (44 lb ft).
17. Install the stabilizer shaft link to the lower control arms.
18. Install the stabilizer shaft link nuts. Tighten: Tighten the nuts to 50 N.m (37 lb ft).
19. Install the lower shock mounting bolts (1). Tighten: Tighten the bolts to 25 N.m (18 lb ft).
20. Install the brake pipe connection to the frame with the nuts (1). Tighten: Tighten the nuts to 10 N.m (89 lb in).
21. Install the BPMV nuts (1). Tighten: Tighten the nuts to 10 N.m (89 lb in).
22. Install the washer bottle bracket and nuts (3). Tighten: Tighten the nuts to 10 N.m (89 lb in).
23. Remove the mechanics wire (3) supporting the radiator.
24. Secure the energy absorber bracket nut (1). Tighten: Tighten the nut to 25 N.m (18 lb ft).
25. Install the antilock brake wiring harness to the lower control arms.
26. Secure the right rearward retainer (1).
27. Secure the left rearward retainer (1).
28. Secure the engine electrical harness retainers (1) to the frame.
29. Install the front air deflector. Refer to «Air Deflector Replacement - Front»(/cadillac/sts/i-2004-2007/remont/exterior-body-panels/#body-front-end) in Body Front End.
30. Install the front tires and wheels. Refer to «Tire and Wheel Removal and Installation»(/cadillac/sts/i-2004-2007/remont/wheel-tire-system/#tires-and-wheels) in Tire and Wheels.
31. Lower the vehicle.
32. Remove the engine support fixture. Refer to the following procedures: «Engine Support Fixture»(/cadillac/sts/i-2004-2007/remont/mechanical/#engine-mechanical-36l-ly7-2-of-6__engine-support-fixture) in Engine Mechanical - 3.6L (LY7) «Engine Support Fixture»(/cadillac/sts/i-2004-2007/remont/mechanical/#engine-mechanical-46l-lh2-2-of-6) in Engine Mechanical - 4.6L (LH2)
33. Align the vehicle. Refer to «Measuring Wheel Alignment»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__measuring-wheel-alignment) in Wheel Alignment.

Tools Required

J 39580 Engine Support Stand. See Special Tools .

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/sts/i-2004-2007/remont/hoistjack/#general-information) in General Information.
2. Remove the rear wheels. Refer to «Tire and Wheel Removal and Installation»(/cadillac/sts/i-2004-2007/remont/wheel-tire-system/#tires-and-wheels) in Tires and Wheels.
3. Remove the exhaust system. Refer to «Exhaust System Replacement»(/cadillac/sts/i-2004-2007/remont/exhaust/#engine-exhaust-system__exhaust-system-replacement) in Engine Exhaust.
4. Remove the driveshaft from the differential. Refer to «Propeller Shaft Replacement - Rear (AWD)»(/cadillac/sts/i-2004-2007/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints__propeller-shaft-replacement-rear-awd) or «Propeller Shaft Replacement - Rear (RWD)»(/cadillac/sts/i-2004-2007/remont/driveshaft-universal-joints/#propeller-shaft-and-universal-joints__propeller-shaft-replacement-rear-rwd) in Propeller Shaft.
5. Install the support fixture (3), in order to raise the lower control arm to relieve the tension from the shock.
6. Remove the shocks lower mounting bolt (2).
7. Remove the support fixture.
8. Disconnect the electrical connectors for the rear wheel speed sensors (WSSs).
9. Disconnect the retainer clips on the park brake cables for the WSSs wiring harness.
10. Disconnect the rear brake pipe lines (1) forward of the rear wheelhouse.
11. Remove the fastener for the brake pipe bracket (1).
12. Remove the brake pipe bracket (2) from the studs in the body.
13. Disconnect the intermediate park brake cable (2) from the front park brake cable connector.
14. Disconnect the intermediate park brake cable (2) from the rear park brake cable connector (1).
15. Position the frame support table J 39580 . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .
16. Using the J 39580 . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .
17. Remove the frame to body mounting bolts (4) and washers (3).
18. Carefully raise the vehicle from the rear frame assembly.
19. Remove the following components from the rear frame: «Headlamp Leveling Sensor Replacement - Rear»(/cadillac/sts/i-2004-2007/remont/exterior-lights/#lighting-systems-introduction) in Lighting Systems «Lower Control Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Upper Control Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension The rear brake pipes «Park Brake Cable Replacement - Left Rear»(/cadillac/sts/i-2004-2007/remont/parking-brake-system/#parking-brake-system) or «Park Brake Cable Replacement - Right Rear»(/cadillac/sts/i-2004-2007/remont/parking-brake-system/#parking-brake-system) in Park Brake «Stabilizer Shaft Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Adjustment Link Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Trailing Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Stabilizer Shaft Link Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Brake Caliper Replacement - Rear (JL9, JE5)»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#disc-brake-system__brake-caliper-replacement-rear-jl9) or «Brake Caliper Replacement - Rear (J56)»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#disc-brake-system__brake-caliper-replacement-rear-j56) in Disc Brakes «Brake Rotor Replacement - Rear»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#disc-brake-system__brake-rotor-replacement-rear) in Disc Brakes «Differential Replacement»(/cadillac/sts/i-2004-2007/remont/differentials-drive-axles/#rear-drive-axle) in Rear Drive Axle
20. With the aid from an assistant, remove the frame from the hydraulic jack.

1. With the aid from an assistant, position and secure the new rear frame (2) on the engine support fixture.
2. Install the following components to the rear frame assembly: «Differential Replacement»(/cadillac/sts/i-2004-2007/remont/differentials-drive-axles/#rear-drive-axle) in Rear Drive Axle «Brake Rotor Replacement - Rear»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#disc-brake-system__brake-rotor-replacement-rear) in Disc Brakes «Brake Caliper Replacement - Rear (JL9, JE5)»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#disc-brake-system__brake-caliper-replacement-rear-jl9) or «Brake Caliper Replacement - Rear (J56)»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#disc-brake-system__brake-caliper-replacement-rear-j56) in Disc Brakes «Stabilizer Shaft Link Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Trailing Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Adjustment Link Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Stabilizer Shaft Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Park Brake Cable Replacement - Left Rear»(/cadillac/sts/i-2004-2007/remont/parking-brake-system/#parking-brake-system) or «Park Brake Cable Replacement - Right Rear»(/cadillac/sts/i-2004-2007/remont/parking-brake-system/#parking-brake-system) in Park Brake The rear brake pipes «Upper Control Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Lower Control Arm Replacement»(/cadillac/sts/i-2004-2007/remont/suspension-rear/#rear-suspension-system) in Rear Suspension «Headlamp Leveling Sensor Replacement - Rear»(/cadillac/sts/i-2004-2007/remont/exterior-lights/#lighting-systems-introduction) in Lighting Systems
3. Index the rear coil springs to the spring insulators.
4. Ensure the intermediate park brake cable is positioned over left side frame assembly on the left side.
5. Lower the vehicle to the frame.
6. Position the coil springs (3) to the upper spring insulator (2).
7. Index the rear side frame mounts to the rear locator sleeves (1) located on the body.
8. Lower the vehicle until the frame mounts contact the body rail.
9. Install the rear frame washers (3) and anchor bolts (4). Tighten: Tighten the front bolts to 265 N.m (195 lb ft). Tighten the rear bolts to 191 N.m (141 lb ft).
10. Raise the vehicle.
11. Remove the J 39580 . See «Special Tools»(/cadillac/sts/i-2004-2007/remont/frames-subframes-crossmembers/#frame-underbody__special-tools) .
12. Install the support fixture (3) in order to raise the lower control arms for ease of lower shock bolt installation (2).
13. Install the lower shock bolt. Tighten: Tighten the bolt (2) to 150 N.m (111 lb ft).
14. Repeat the above step for the other side.
15. Remove the support fixture (3).
16. Connect the intermediate park brake cable (2) to the rear park brake cable connector (1).
17. Connect the intermediate park brake cable (2) to the front park brake cable connector.
18. Position the brake pipe bracket (2) to the body studs.
19. Install the brake pipe bracket retaining nuts (1). Tighten: Tighten the nuts to 10 N.m (89 lb in).
20. Connect the rear brake lines (1) at the forward rear wheelhouse. Tighten: Tighten the lines to 15 N.m (11 lb ft).
21. Connect the rear WSS electrical connectors.
22. Secure the electrical harness retainer clips to the park brake cables.
23. Install the rear wheels. Refer to «Tire and Wheel Removal and Installation»(/cadillac/sts/i-2004-2007/remont/wheel-tire-system/#tires-and-wheels) in Tires and Wheels.
24. Lower the vehicle.
25. Bleed the hydraulic brake system. Refer to «Hydraulic Brake System Bleeding (Manual)»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#hydraulic-brake-system) or «Hydraulic Brake System Bleeding (Pressure)»(/cadillac/sts/i-2004-2007/remont/mechanical-hydraulic/#hydraulic-brake-system) in Hydraulic Brakes.
26. Align the vehicle. Refer to «Measuring Wheel Alignment»(/cadillac/sts/i-2004-2007/remont/wheel-alignment/#wheel-alignment-system__measuring-wheel-alignment) in Wheel Alignment.

1. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/sts/i-2004-2007/remont/hoistjack/#general-information) in General Information.
2. Remove and support the exhaust from the catalytic converters. Refer to «Exhaust System Replacement»(/cadillac/sts/i-2004-2007/remont/exhaust/#engine-exhaust-system__exhaust-system-replacement) in Engine Exhaust.
3. Remove the transmission mount lower mounting nuts.
4. Support the transmission with a screw jack and block of wood.
5. Remove the outer transmission mounting bolts.
6. Remove the inner transmission mounting bolts.
7. Remove the transmission support from the vehicle.

1. Install the transmission support to the vehicle.
2. Install the inner transmission support mounting bolts. Do not tighten at this time.
3. Install the outer transmission mounting bolts. Tighten: Tighten all the support bolts to 60 N.m (44 lb ft).
4. Remove the screw jack.
5. Install the transmission mount lower mounting nuts. Tighten: Tighten the nuts to 60 N.m (44 lb ft).
6. Install the exhaust system to the catalytic converters. Refer to «Exhaust System Replacement»(/cadillac/sts/i-2004-2007/remont/exhaust/#engine-exhaust-system__exhaust-system-replacement) in Engine Exhaust.
7. Remove the support from the exhaust system.
8. Lower the vehicle.

Frame and Underbody Description

The following components are supported by a front crossmember frame which is rigidly bolted to the body rail at 4 locations

1. The engine
2. The transmission mounts
3. The front suspension lower control arms
4. The steering linkage

The following components are supported by the rear suspension frame which is attached to the body rail through rubber insulators at 3 locations

1. The rear differential
2. The rear axles
3. The rear suspension components

The underbody frames must be properly aligned to maintain the correct suspension and wheel alignment.

The individual underbody components contribute directly to the overall strength of the unibody. Use proper welding techniques during service repair operations. Refer to Collision Repair for welding information and for vehicle preparation.

The components must be corrosion protected whenever body repair operations damage or destroy the original sealing surfaces. Use a two part catalyzed primer such as PPG DP40 or equivalent when corrosion protection is needed to welded surfaces. Apply the sealers and anti-corrosion materials as necessary. Refer to Anti-Corrosion Treatment and Repair in Paint and Coatings. Do not combine paint systems. Refer to Basecoat/Clearcoat Paint Systems in Paint and Coatings for further information.

Special Tools

Special Tools Illustration Tool Number/ Description J 24319-B Steering Linkage and Tie Rod Puller J 39580 Engine Support Stand

Scheme 1

Scheme 2

See also:
• Lifting and Jacking the Vehicle
• Engine Support Fixture
• Engine Support Fixture
• Tire and Wheel Removal and Installation
• Air Deflector Replacement - Front
• Lower Control Arm Replacement
• Fastener Notice
• Measuring Wheel Alignment
• Exhaust System Replacement
• Propeller Shaft Replacement - Rear (AWD)
• Propeller Shaft Replacement - Rear (RWD)
• Headlamp Leveling Sensor Replacement - Rear
• Lower Control Arm Replacement
• Park Brake Cable Replacement - Left Rear
• Brake Caliper Replacement - Rear (JL9, JE5)
• Brake Caliper Replacement - Rear (J56)
• Brake Rotor Replacement - Rear
• Differential Replacement
• Hydraulic Brake System Bleeding (Manual)
• Anti-Corrosion Treatment and Repair
• Basecoat/Clearcoat Paint Systems
• Special Tools