GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Blazer - 4WD - RHD 🢒 Body and Accessories 🢒 Frame and Underbody 🢒 Frame Conditions
Table 1: Sag
Table 2: Buckle
Table 3: Sidesway
Table 4: Diamond
Table 5: Twist
Table 6: Improper Tracking
Table 7: Cracks in Web of Rails

Sag

Problem

Action

The load is greater than the frame is designed to carry.

Straighten and reinforce the frame. Refer to Straightening Frames.

There is uneven load distribution.

There is improper body or accessory mounting:

    • Holes are drilled in the flange of the frame rail.
    • The holes in the web section are too close to each other.
    • Four or more rails are in the same vertical line of the rail web.
    • There are welds on the flange, particularly across the flange or along its edge.
    • Cutting holes in the rail with a torch.
    • There are cutting notches anywhere on the rails.

There is a fire involving the vehicle.

There is a collision involving the vehicle.

The use of the equipment for which the frame has not been designed or reinforced.

Buckle

Problem

Action

The use of equipment such as snow plows for which the frame is not designed.

Straighten and reinforce the frame. Refer to Straightening Frames.

There is a collision involving the vehicle.

There is a fire involving the vehicle.

There are abrupt changes in section modules.

There is improper body or accessory mounting:

    • Holes are drilled in the flange of the frame rail.
    • The holes in the web section are too close to each other.
    • Four or more rails are in the same vertical line of the rail web.
    • There are welds on the flange, particularly across the flange or along its edge.
    • Cutting holes in the rail with a torch.
    • There are cutting notches anywhere on the rail.

Sidesway

Problem

Action

The vehicle is involved in a collision.

Straighten and reinforce the frame. Refer to Straightening Frames.

The vehicle is involved in a fire.

The vehicle uses equipment such as snow plows for which the frame was neither designed nor properly reinforced.

There are abrupt changes in section modules.

There is improper body or accessory mounting:

    • Holes are drilled in the flange of the frame rail.
    • The holes in the web section are too close to each other.
    • Four or more rails are in the same vertical line of the rail web.
    • There are welds on the flange, particularly across the flange or along its edge.
    • Cutting holes in the rail with a torch.
    • There are cutting notches anywhere on the rails.

Diamond

Problem

Action

There is a collision involving the vehicle.

Straighten and reinforce the frame. Refer to Straightening Frames.

The vehicle was towed with a chain attached to one corner of the frame.

Twist

Problem

Action

There is an accident or collision involving the vehicle.

Straighten and reinforce the frame. Refer to Straightening Frames.

The vehicle is operated in very rough terrain.

Improper Tracking

Problem

Action

The frame is out of alignment.

Replace or weld and reinforce the rail. Ream bolt holes and replace the bolts with larger bolts, if necessary. Retighten the bolts.

The front or rear axle has shifted.

Replace or weld and reinforce the rail.

There is incorrect wheel alignment.

Refer to Front Wheel Alignment.

Cracks in Web of Rails

Problem

Action

There are loose crossmember attaching bolts.

Replace or weld and reinforce the rail. Ream bolt holes and replace the bolts with larger bolts if necessary. Retighten the bolts.

There is concentration of stress that may result from many different factors.

Replace or weld and reinforce the rail.