Frame and Underbody Buick Century VI

Fastener Tightening Specifications

TIGHTENING SPECIFICATIONS

Alignment Checking

Use a measuring tram gage in order to determine the alignment of the underbody. In order to perform the recommended measuring inspections, the tram gage set must include a vertical pointer capable of reaching 914 mm (36 in).

You may make the following measurements using a tram gage

1. Direct point-to-point measurements
2. Measurements you calculate on a horizontal plane (datum line) parallel to the underbody For each point to be measured, set one of the following pointers as specified: The height pointer The vertical pointer

Take the point-to-point measurements from the following components

1. The front structure steering component
2. The suspension component

Ensure that the vertical pointers are equally set. In some cases, you may directly take point-to-point measurements using one of the following tools

1. A tape measure
2. An appropriate measuring tool

Measure the dimensions-to-gage holes to the following areas

1. The leading edge or center of the holes
2. The flush-to-adjacent surface metal

Refer to Dimensions - Body in Collision Repair for the following information

1. The alphabetically identified points of measurement
2. The metric-to-English dimensional conversion data

Underbody Inspection

1. Raise and suitably support the vehicle. Refer to LIFTING AND JACKING THE VEHICLE in General Information.
2. Check for obvious deterioration on 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. Perform all repairs 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. Open the drain holes in the body side panels using a punch and a drift.

Tools Required

J 39580 Universal Engine Support Table

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1. Install the engine support fixture. Refer to the following procedures: ENGINE SUPPORT FIXTURE in Engine Mechanical - 3.1 L ENGINE SUPPORT FIXTURE in Engine Mechanical - 3.8L
2. Raise and support the vehicle. Refer to LIFTING AND JACKING THE VEHICLE in General Information.
3. Remove the front tires and wheels. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
4. Remove the radiator lower air deflector. Refer to RADIATOR AIR BAFFLE AND DEFLECTOR REPLACEMENT - LOWER in Engine Cooling.
5. Disconnect the fog lamp electrical connectors and position aside.
6. Remove the positive battery cable and retainers from the frame and position the cable aside. Refer to BATTERY POSITIVE CABLE REPLACEMENT in Engine Electrical.
7. Disconnect the power steering cooler pipe from the frame. Refer to POWER STEERING COOLER PIPE/HOSE REPLACEMENT in Power Steering System.
8. Secure the power steering cooler.
9. Remove the stabilizer shaft links and rotate the stabilizer shaft up in order to gain access to the mounting bolts on the power steering gear. Refer to STABILIZER SHAFT LINK REPLACEMENT in Front Suspension.
10. Remove the mounting bolts. Refer to POWER STEERING GEAR REPLACEMENT in Power Steering System.
11. Secure the power steering gear.
12. Remove the nuts that secure the engine mount to the frame. Refer to the following procedures: ENGINE MOUNT REPLACEMENT in Engine Mechanical - 3.1 L ENGINE MOUNT AND BRACKET REPLACEMENT in Engine Mechanical - 3.8L
13. Remove the nuts which secure the transaxle mount to the frame. Refer to Automatic Transmission Mount Replacement in Automatic Transaxle.
14. Disconnect both front wheel speed sensor connectors (1), if equipped.
15. Remove both speed harness retainers (2) from the frame and the lower control arms, if equipped.
16. Separate both of the lower ball joints from the steering knuckle. Refer to LOWER CONTROL ARM REPLACEMENT in Front Suspension.
17. Lower the vehicle until the frame contacts J 39580.
18. Remove and DISCARD the bolts which secure the front frame to the body.
19. Remove the bolts which secure the rear frame to the body.
20. Raise the vehicle in order to separate the frame from the body.
21. If you are replacing the frame, remove the following components: Both of the lower control arms - refer to LOWER CONTROL ARM REPLACEMENT in Front Suspension The stabilizer shaft - refer to STABILIZER SHAFT REPLACEMENT in Front Suspension The spacers, the upper insulator, the lower insulator, and the retainers - refer to «FRAME CUSHION OR INSULATOR REPLACEMENT - FRONT»(/buick/century/vi-1997-2005/remont/frames-subframes-crossmembers/#frame-and-underbody__frame-cushion-or-insulator-replacement) and to «FRAME CUSHION OR INSULATOR REPLACEMENT - REAR»(/buick/century/vi-1997-2005/remont/frames-subframes-crossmembers/#frame-and-underbody)

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1. If you are replacing the frame, install the following components: Both of the lower control arms - refer to LOWER CONTROL ARM REPLACEMENT in Front Suspension The stabilizer shaft - refer to STABILIZER SHAFT REPLACEMENT in Front Suspension The spacers, the upper insulator, the lower insulator, and the retainers - refer to «FRAME CUSHION OR INSULATOR REPLACEMENT - FRONT»(/buick/century/vi-1997-2005/remont/frames-subframes-crossmembers/#frame-and-underbody__frame-cushion-or-insulator-replacement) and to «FRAME CUSHION OR INSULATOR REPLACEMENT - REAR»(/buick/century/vi-1997-2005/remont/frames-subframes-crossmembers/#frame-and-underbody)
2. Position the engine support table with the frame under the vehicle.
3. Lower the vehicle to the frame.
4. Loosely install the bolts which secure the rear frame to the body.
5. Loosely install the bolts which secure the front frame to the body.
6. Align the frame to the body by inserting two 19x203 mm (0.74x8.0 in) pins in the alignment holes on the right side of the frame.
7. Install the frame bolts. Tighten Tighten the bolts to 180 N.m (133 lb ft).
8. Connect both the lower ball joints to the steering knuckle. Refer to LOWER BALL JOINT REPLACEMENT in Front Suspension.
9. Install the nuts which secure the engine mount to the frame. Refer to the following procedures: ENGINE MOUNT REPLACEMENT in Engine Mechanical - 3.1 L ENGINE MOUNT AND BRACKET REPLACEMENT in Engine Mechanical - 3.8L
10. Install the nuts which secure the transaxle mount to the frame. Refer to Automatic Transmission Mount Replacement in Automatic Transaxle.
11. Install the steering gear mounting bolts. Refer to POWER STEERING GEAR REPLACEMENT in Power Steering System.
12. Install the stabilizer shaft links. Refer to STABILIZER SHAFT LINK REPLACEMENT in Front Suspension.
13. Connect both speed sensor connectors (1) to the front wheels, if equipped.
14. Install both front wheel speed harness retainers (2) to the frame and to the lower control arm, if equipped.
15. Install the positive battery cable and retainers to the frame. Refer to BATTERY POSITIVE CABLE REPLACEMENT in Engine Electrical.
16. Install the power steering cooler pipe. Refer to POWER STEERING COOLER PIPE/HOSE REPLACEMENT in Power Steering System.
17. Install the radiator lower air deflector. Refer to RADIATOR AIR BAFFLE AND DEFLECTOR REPLACEMENT - LOWER in Engine Cooling.
18. Connect the fog lamp electrical connectors.
19. Install the front tires and wheels. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
20. Lower the vehicle.
21. Remove the engine support fixture. Refer to the following procedures: ENGINE SUPPORT FIXTURE in Engine Mechanical - 3.1 L ENGINE SUPPORT FIXTURE in Engine Mechanical - 3.8L
22. Inspect the front wheel alignment. Refer to MEASURING WHEEL ALIGNMENT in Wheel Alignment.

Frame Cushion or Insulator Replacement - Front

Tools Required

J 45296 Frame Insulator Remover/Installer

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1. Raise and support the vehicle. Refer to LIFTING AND JACKING THE VEHICLE in General Information.
2. Remove the intermediate steering shaft. Refer to INTERMEDIATE STEERING SHAFT REPLACEMENT in Steering Wheel and Column.
3. Disconnect the fog lamp electrical connectors from the fog lamps.
4. Install a jackstand under the center of the frame, between the front frame insulators.
5. Remove the front frame bolts and retainers.
6. Lower the front of the frame.
7. Remove the frame front upper insulators.
8. Install the J 45296, or equivalent to the front frame insulator that you are removing.
9. Using the J 45296, or equivalent remove the front insulator from the frame.

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1. Clean the front frame insulator opening.
2. Apply a thin coat of rubber lubricant GM P/N 01051717 (Canadian P/N 12345884) or equivalent to the inside of the front frame insulator opening and to the front frame insulator.
3. Align the front frame insulator to the opening with the alignment tabs facing to the front.
4. Using the J 45296, or equivalent install the insulator to the front frame.
5. Install the frame front upper insulators.
6. Raise the front of the frame.
7. Install the front frame bolts and retainers. Tighten Tighten the bolts to 180 N.m (133 lb ft).
8. Remove the jackstand.
9. Connect the fog lamp electrical connectors to the fog lamps.
10. Connect the steering intermediate shaft. Refer to INTERMEDIATE STEERING SHAFT REPLACEMENT in Steering Wheel and Column.
11. Lower the vehicle.

Removal Procedure

When installing a body mount, ensure the lower insulator is seated into the frame. The lower insulator should not be loose. The spacer and the corresponding upper insulator is pressed into the lower insulator thus squeezing the frame. The bolt is then inserted through the mount, capturing the lower retainer. The body mount components prevent contact of the frame to the body.

Do not over tighten the body mount. Over tightening may collapse a spacer or strip a bolt. When the frame insulator bolts are removed, always discard the bolts and replace with new bolts.

When clamping by the mount, ensure the surfaces are clean and dry. If the frame insulator bolt does not screw in smoothly, run a tap through the frame crossmember nut in the body in order to remove foreign material. Ensure the tap does not punch through the underbody.

Whenever the body is moved in relation to the frame, disconnect the intermediate shaft from the rack and pinion steering gear and stub shaft.

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1. Raise and suitably support the vehicle. Refer to LIFTING AND JACKING THE VEHICLE in General Information.
2. Remove the intermediate shaft from the steering gear stub shaft. Refer to INTERMEDIATE STEERING SHAFT REPLACEMENT in Power Steering System.
3. Install a utility stand to the rear of the frame.
4. Remove the rear frame bolts.
5. Lower the rear of the frame.
6. Remove the upper and lower insulators from the rear of the frame as a set.

Installation Procedure

1. Apply lube to inside surface of lower insulator and to top surface of upper insulator.
2. Install the upper and lower insulators to the rear of the frame as a set.
3. Raise the rear of the frame.
4. Install the rear frame bolts. Tighten Tighten the bolts to 180 N.m (133 lb ft).
5. Remove the utility stand.
6. Install the intermediate shaft to the steering gear stub shaft. Refer to INTERMEDIATE STEERING SHAFT REPLACEMENT in Power Steering System.
7. Lower the vehicle.

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1. Disconnect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Engine Electrical.
2. Remove carpet in trunk area.
3. Remove the rear suspension support bolt.
4. Place a center punch through the damaged rear suspension support nut. Strike the center punch using a hammer. The punch will leave a dimple on the floor. Use the dimple in order to locate the area where the frame crossmember nut will be removed. IMPORTANT: Do not cut or damage the adjacent panels or the reinforcements.
5. Use a cutoff wheel in order to cut an access panel using a cutoff wheel.
6. Lift the panel upward in order to gain access to the frame crossmember nut retainer. IMPORTANT: Reuse the frame crossmember nut retainer if the retainer is not damaged from the stripped out bolt.
7. Use an air chisel in order to break away the spot welds (1) on one side of the frame crossmember nut retainer.
8. Lift one side of the frame crossmember nut retainer (3) enough in order to remove the frame crossmember nut (2).
9. Remove the rear suspension support nut.

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1. Install the rear suspension support nut.
2. Lower the frame crossmember nut retainer into place. Ensure that the following conditions exist: The frame crossmember nut is correctly positioned. The frame crossmember nut operates correctly.
3. Spot weld the frame crossmember nut retainer in the original location.
4. Clean and prepare the welded surfaces.
5. Apply corrosion protection. Refer to Anti-Corrosion Treatment and Repair in Paint Coatings.
6. Install the new rear suspension support bolt to the frame crossmember nut. Tighten Tighten the bolt to 50 N.m (37 lb ft).
7. Reposition the panel downward to the original position.
8. Stitch weld the panel back to the original position using 25 mm (0.98 in) welds along the seam. Leave 25 mm (0.98 in) gaps between the welds. A solid joint with minimal heat distortion will result. Continue to finish the stitch weld procedure.
9. Use a small grinder in order to remove the excess material from the floor panel until the following conditions exist: The floor panel is smooth. The floor panel is free from rough edges.
10. Clean and prepare the welded surfaces.
11. Apply corrosion protection. Refer to Anti-Corrosion Treatment and Repair in Paint and Coatings.
12. Let the primer dry for approximately 30 minutes. Then apply Dominion Sure Seal P/N 110900 Sound Deadener or the equivalent to the repair area.
13. Reposition the carpet and the pad over the repair area.
14. Apply anti-corrosion compound GM P/N 12346225 or equivalent. Thoroughly coat the inside of the repair area through the access hole.
15. Connect the negative battery cable. Refer to BATTERY NEGATIVE CABLE DISCONNECT/CONNECT PROCEDURE in Engine Electrical.

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1. Raise and support the vehicle. Refer to LIFTING AND JACKING THE VEHICLE in General Information.
2. Remove the front tires and wheels. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
3. Install a jackstand under the frame near the rear cage nut that you are replacing.
4. If you are replacing the FRONT cage nut, remove the front impact bar to gain access. Refer to IMPACT BAR REPLACEMENT - FRONT BUMPER in Bumpers. If you are replacing the REAR cage nut, perform the following steps to gain access.
5. Using a small flat-bladed tool, remove the access panel of the right rear cage nut.
6. In order to remove the access panel of the left rear cage nut, remove the fuel line bracket bolt and position the fuel lines slightly forward.
7. Using a small flat-bladed tool, remove the access panel of the left rear cage nut. CAUTION: Approved safety glasses and gloves should be worn when performing this procedure to reduce the chance of personal injury.
8. Remove the rear frame-to-body bolts.
9. In order to break the spot welds free on the rear cage nut retainer, insert an air-hammer and a 152 mm (6 in) punch or equivalent through the rear frame insulator and position the air-hammer against the rear cage nut.
10. Hold the air-hammer firmly and apply pressure in order to free the rear cage nut. CAUTION: The edges of the rear cage nut retainer are sharp. In order to avoid personal injury, use care when removing the rear cage nut from the access opening.
11. Reach into the access opening and carefully raise the rear cage nut retainer up.
12. Remove the rear cage nut.

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1. Install the rear cage nut into the access opening.
2. Press the retainer over the rear cage nut in order to hold the nut in place.
3. Loosely install the rear frame bolts through the frame and into the rear cage nut. Hold the rear cage nut down with your finger in order to start the rear frame bolt. Tighten Tighten the bolts to 180 N.m (133 lb ft).
4. Install the access panel of the right rear cage nut.
5. Install the access panel of the left rear cage nut.
6. If necessary, install the fuel line bracket bolt. Tighten Tighten the bolt to 20 N.m (15 lb ft).
7. Remove the jackstand.
8. Install the tires and wheels. Refer to TIRE AND WHEEL REMOVAL AND INSTALLATION in Tires and Wheels.
9. Lower the vehicle.

Datum Description

The datum line is a base line parallel to the plane of the underbody or frame. All vertical measurements originate from the datum line. A datum line is an imaginary horizontal plane that runs below and parallel to the vehicle. Height dimensions are calculated at right angles from the datum to a given control or reference point on the underbody.

Height dimensions determine the location of the datum based on the equipment being used. Therefore, different datum lines are established for the same vehicle. You may add or subtract an equal amount from all height dimensions and create a new datum line for your use.

Centerline Description

A centerline is an imaginary vertical plane that is perpendicular to the length of the datum plane through the center of the vehicle. The centerline is a line drawn through the center of the vehicle's datum plane.

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See also:
• FRAME CUSHION OR INSULATOR REPLACEMENT - FRONT
• FRAME CUSHION OR INSULATOR REPLACEMENT - REAR