The main parts of a frame are the side rails and the crossmembers. The side rails carry the load. The crossmembers stabilize the rails.
There are 5 types of frame misalignment:
| • | Sag |
| • | Buckle |
| • | Diamond |
| • | Sidesway |
| • | Twist |
For a brief definition of the 5 types of frame misalignment, refer to Frame and Underbody Description .
Consider the following locations when you suspect misalignment:
| • | Forward from where the frame should be |
| • | Up or down from where the frame should be |
| • | To the side of where the frame should be |
Inspect the frame alignment using gauges made for that purpose. Detailed instructions are normally supplied with the gauges at the time of purchase. Instructions for gauge use are not given in this manual.
You may inspect certain portions of frame alignment without the proper gauges.
Whether alignment is inspected with or without gauges, ensure that the vehicle is parked on a level section of the floor.
Certain conditions require preliminary inspections before you inspect the frame. Suspension or axle problems may make the vehicle frame look out of alignment. If an axle has shifted, a diamond or sidesway may appear to exist. A weak spring may make the vehicle appear to have a twisted frame.
A visual inspection of the top and the bottom flanges of each rail may reveal the specific area where sag or buckle exists. Wrinkles that appear on the top of the upper flange are evidence of sag. Wrinkles that appear on the bottom of the lower flange are evidence of buckle.
