During the past several years, the growing popularity of pickups and
SUVs have created problems in the repair shop. Many technicians are not
comfortable with body-over-frame vehicles, and determining whether to
repair or replace a frame is just the beginning of the challenge.By Bruce Peters
Contributing EditorFor years, collision repair shops have focused on structural repair to unibody vehicles. Now, many repairers are finding their technicians don't have the skills necessary to repair full-frame vehicles. Increasingly, collision shops and insurance companies are having a difficult time making repair or replace decisions when working with body-over-frame (BOF) vehicles. As the growth in the popularity of light trucks and SUVs that use this type of construction increases, the problem is becoming more acute.Let's take a look at the problem. Whether we're dealing with the collision or insurance industries, the problem lies in the experience of dealing with BOF vehicles- SUVs, and pickups. Much of this experience problem can be tracked in the history of collision shops and technicians.In the late '70s and early '80s, the introduction of the unibody forced most collision shops to start doing their own "frame" work. Before this, most shops sent their work to a shop that specialized in pulling and straightening vehicles. This work involved straightening the frame on the BOF vehicle before it was returned to the body shop so that replacement sheet metal could be hung or repaired as necessary. This process meant that very few technicians understood the pulling and anchoring of BOF vehicles.Many technicians today learned to straighten unibody vehicles and have very little knowledge of the techniques used for frame repair. These technicians, when confronted with the challenges posed by the BOF construction of SUVs, attempt to adapt unibody repair techniques to full-frame vehicles.In many cases, this makes it very difficult to get the job done. When it comes to making repair-or-replace decisions, technicians need to realize that these are two different constructions that lead to two different methods of repair vs. replace.The information we receive through training classes typically deals primarily with unibody vehicles. We receive very little information on BOF vehicles.But this does not mean information is not available. Most OEMs have repair manuals available to us. For example, General Motors (GM) has an informative body repair manual giving us procedures for replacing or sectioning its front or rear rails. DaimlerChrysler and Ford also have repair procedures that need to be followed when repairing their full-frame vehicles. Ford vehicles are probably the most difficult to make repair-or-replace decisions on because of the convolutions designed into the manufacturer's frames. But Ford's recommendation in its repair manual states: "Warning: Straightening of front frame rail convolutes is prohibited" (See Fig. 1).Just like working on a unibody, you need to know what may be sectioned, replaced or repaired by using the manufacturers' manuals or other information training organizations.Let's take a look at some of these problems dealing with full-frame vehicles.Anchoring: When anchoring, nothing really changes. When we anchor a unitized vehicle, we're using positive anchoring on the pinchwelds. But, when using a chain to anchor a full-frame vehicle, the problem lies in getting the vehicle secure-no slack. We still are going to use the four torque boxes. Most frame manufacturers make positive anchoring. This takes a lot of the problem away. Ask your equipment manufacturer for information dealing with BOF repairs.Measuring and Damage Diagnosis: When measuring full-frame vehicles, the procedure stays the same. Unlike a very rigid unitized body, the BOF vehicle is very flexible. Perimeter frames have a lot of deflection, which means that when the vehicle is put up on stands near the torque boxes, the front may sag 20 mm to 25 mm downward, depending on the mechanicals. Ladder-pickup-frames are meant to twist if they are not anchored solidly. You may read a misalignment in the base or foundation (front and rear torque boxes), which is why it is essential to be level and square with your center section or base (See Fig. 2).Pulling: When pulling a full frame, the problem is not just the power but how the power is applied. In many cases, technicians do not place their clamps in the most efficient places. When placing a pulling clamp, you must consider how the energy or force is going to travel. For instance, if a part is bent or kinked, you should always place the clamp to the side of the bent or kinked side. Most frame members will either be boxes or C-channeled. If you look at the opposite side of a bent or kinked frame member, you'll find that side is longer than it should be. Why would you clamp and pull a side that is longer?Straightening: When straightening on a full-frame vehicle, we have a tendency to apply the knowledge we acquired from making unibody repairs. This is not all wrong, but we need to change our technique. On some of these full-frame vehicles, we need to turn to kinked vs. bend. Ford says to follow I-CAR's kinked vs. bend procedure and to not exceed more than 1,200
Contributing EditorFor years, collision repair shops have focused on structural repair to unibody vehicles. Now, many repairers are finding their technicians don't have the skills necessary to repair full-frame vehicles. Increasingly, collision shops and insurance companies are having a difficult time making repair or replace decisions when working with body-over-frame (BOF) vehicles. As the growth in the popularity of light trucks and SUVs that use this type of construction increases, the problem is becoming more acute.Let's take a look at the problem. Whether we're dealing with the collision or insurance industries, the problem lies in the experience of dealing with BOF vehicles- SUVs, and pickups. Much of this experience problem can be tracked in the history of collision shops and technicians.In the late '70s and early '80s, the introduction of the unibody forced most collision shops to start doing their own "frame" work. Before this, most shops sent their work to a shop that specialized in pulling and straightening vehicles. This work involved straightening the frame on the BOF vehicle before it was returned to the body shop so that replacement sheet metal could be hung or repaired as necessary. This process meant that very few technicians understood the pulling and anchoring of BOF vehicles.Many technicians today learned to straighten unibody vehicles and have very little knowledge of the techniques used for frame repair. These technicians, when confronted with the challenges posed by the BOF construction of SUVs, attempt to adapt unibody repair techniques to full-frame vehicles.In many cases, this makes it very difficult to get the job done. When it comes to making repair-or-replace decisions, technicians need to realize that these are two different constructions that lead to two different methods of repair vs. replace.The information we receive through training classes typically deals primarily with unibody vehicles. We receive very little information on BOF vehicles.But this does not mean information is not available. Most OEMs have repair manuals available to us. For example, General Motors (GM) has an informative body repair manual giving us procedures for replacing or sectioning its front or rear rails. DaimlerChrysler and Ford also have repair procedures that need to be followed when repairing their full-frame vehicles. Ford vehicles are probably the most difficult to make repair-or-replace decisions on because of the convolutions designed into the manufacturer's frames. But Ford's recommendation in its repair manual states: "Warning: Straightening of front frame rail convolutes is prohibited" (See Fig. 1).Just like working on a unibody, you need to know what may be sectioned, replaced or repaired by using the manufacturers' manuals or other information training organizations.Let's take a look at some of these problems dealing with full-frame vehicles.Anchoring: When anchoring, nothing really changes. When we anchor a unitized vehicle, we're using positive anchoring on the pinchwelds. But, when using a chain to anchor a full-frame vehicle, the problem lies in getting the vehicle secure-no slack. We still are going to use the four torque boxes. Most frame manufacturers make positive anchoring. This takes a lot of the problem away. Ask your equipment manufacturer for information dealing with BOF repairs.Measuring and Damage Diagnosis: When measuring full-frame vehicles, the procedure stays the same. Unlike a very rigid unitized body, the BOF vehicle is very flexible. Perimeter frames have a lot of deflection, which means that when the vehicle is put up on stands near the torque boxes, the front may sag 20 mm to 25 mm downward, depending on the mechanicals. Ladder-pickup-frames are meant to twist if they are not anchored solidly. You may read a misalignment in the base or foundation (front and rear torque boxes), which is why it is essential to be level and square with your center section or base (See Fig. 2).Pulling: When pulling a full frame, the problem is not just the power but how the power is applied. In many cases, technicians do not place their clamps in the most efficient places. When placing a pulling clamp, you must consider how the energy or force is going to travel. For instance, if a part is bent or kinked, you should always place the clamp to the side of the bent or kinked side. Most frame members will either be boxes or C-channeled. If you look at the opposite side of a bent or kinked frame member, you'll find that side is longer than it should be. Why would you clamp and pull a side that is longer?Straightening: When straightening on a full-frame vehicle, we have a tendency to apply the knowledge we acquired from making unibody repairs. This is not all wrong, but we need to change our technique. On some of these full-frame vehicles, we need to turn to kinked vs. bend. Ford says to follow I-CAR's kinked vs. bend procedure and to not exceed more than 1,200
