yo E,
Here are dimensions for 92-96 that have the Convolutes, Frame Rail (often called Crumple Zone & accordion) in front that are part of the crash protection design
*** The 91 does not have this crumple zone.***
This is by Steve; "...The 80-81 frame is dimensionally identical to the 82-86 frame; the only difference is the lightening holes. The 87-91 frame has some extra slots in the front horns for that style of front bumper bracket, and possibly a minor change to the front body mount (core support mount).
The accordion (crumple zone) frame is 2 inches longer in front than the others, though its bumper mounting tabs are about 1 inch closer to the core support. Most also have a reinforcement along the top edge at the lowest point (under the front doors)."
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1996 F-150, F-250, F-350, F-Super Duty Chassis Cab and Bronco Workshop Manual (PARTIAL)
http://www.diesel-dave.com/vehic/manual/stj/stjleft.htm
Same as most earlier years exc. for OBD II in 96, 4WABS (93-96); ABS (87-92); Air Bag (94-96); 3 ***** Automatic Locking Hubs (Built from May 95 through 96); Spark Plug Wire Routing & Firing Order (The firing order for 1987-1993 5.0Ls is 1-5-4-2-6-3-7-8. The firing order for 1994- 96 5.0Ls & all 5.8Ls is 1-3-7-2-6-5-4-8.);
2-piece Spindle Rolling Diaphragm Seal (RDS) used on 5/95 to 96 Broncos & F Series 1/2-ton 4WD
and a few other items that I still need to research
See Section 02-01: Frame
SERVICE PROCEDURES
Diagonal or X-Frame Checking Method
NOTE: An alternate method of checking frame alignment is to use a frame gauge.
Frame alignment can be checked without removing the body from the frame (5005) by using the diagonal or X-frame checking method.
This method should be used to identify misalignment prior to any attempt to straighten a frame.
1.Place the vehicle on a clean, level floor and set the parking brake.
2.Select at least four points along the left frame side rail (5015) and transfer these points to the floor with a plumb bob. If desired, paper can be taped on the floor along both sides of the vehicle below the frame. Mark the points on the floor as accurately as possible.
3.Locate the corresponding points along the right frame side rail (5016) and transfer these points to the floor in the same manner.
4.Move the vehicle away from the marks on the floor, and measure diagonally between all points on the floor. Both measurements should be equal within 6.35mm (1/4 inch).
5.Measure between corresponding points parallel to the frame side rails. These measurements should be within 3.18mm (1/8 inch) of each other.
The squareness of the frame side rail web to the floor at the spring hangers and at the steering gear mounting location should be within 1.59mm (1/16 inch). The squareness of the frame side rail web to the floor at all other points should be within 3.18mm (1/8 inch). The web and ****** should be square at all other points within 3.18mm (1/8 inch).
Any point on one side rail should be within 3.18mm (1/8 inch) ahead, behind, above, or below the corresponding point on the opposite side rail. The frame side rail should not be bowed more than 3.18mm (1/8 inch) for each 2540mm (100 inches) of frame length. The overall width of the frame should not vary more than 3.18mm (1/8 inch).
An alternate method of checking frame alignment is to use Rotunda Laser Measuring System 073-00451 or equivalent.