Trial Fit Parts?

Where do replacement parts come from? You probably assumed they come directly from the OEM, aftermarket manufacturers or recycled (a.k.a. salvage) parts suppliers. In actuality, the number of places that replacement parts come from can vary from manufacturer to manufacturer.

OEM "factory" parts can come from a number of different suppliers. The most obvious would be the factory assembly line, but in most cases they do not. The factory needs parts to build vehicles, so OEMs hire companies categorized as tier one, two or three level to produce their parts. These companies use OEM-certified equipment with restrictions on how many times the press dies can be used before being changed. Some OEM parts rejected off the assembly line are boxed and sold to repair facilities. This clearly establishes that all parts are not created equally, and many parts that don't make the manufacturers' cut do eventually wind up on vehicles.

Aftermarket parts come from companies that reproduce OEM-like parts ("knockoffs") as an option to save money on OEM replacement parts, and from companies that produce parts such as spoilers, ground effects, carbon fiber and fiberglass replacement body panel parts to enhance, lighten or increase performance and/or appearance. Another source of aftermarket parts would be recycled (a.k.a. salvage) parts from "total loss" collision-damaged vehicles or vehicles that are not worthy of mechanical repair. Most in the auto body repair field have noticed the difference in fit and finish between OEM and second-source parts. However, now that we know where the parts we use in the collision repair field originate, we can turn our attention to how their use on a structurally-damaged vehicle will impact our repair (no pun intended).

As previously stated, not all parts are created equally. We also need to understand that not all collision damage is created the same way. Let's look at a common scenario that almost every body shop goes through on a weekly basis: A side hit repair. But for this example, we will make it a little difficult. The collision-damaged vehicle needs a fender, two doors, a quarter panel and a B-pillar. All the damage is to the left side of the vehicle. The year, make and model are not that important, but let's use a 2010 Chevrolet Malibu, which is found in almost every market area. The vehicle will be structurally realigned on a Car-o-Liner Quick 42 with Vision X3 measuring and EVO 1-3. (Other choices could be a Celette or a Car Bench structural realignment apparatus). As far as parts, we will be fair and use various sources. We will be using an aftermarket fender (we know GM does not recommend A/M parts, and we agree, but bear with us), an LKQ/used/salvage front door (we also know GM does not recommend salvaged parts), a new OEM rear door, quarter panel and the inner reinforcement and outer B-pillar — although we do not recommend you use a "used" welded-on outer or structural panels. We will not cover all the procedures, so we will skip to the installation process after the realignment repairs are complete. The first part to be installed is the B-pillar, following GM's specific repair procedures for this vehicle. (These procedures can be found on GM's free website at www.goodwrench.com/gmgoodwrenchjsp/gmspo/index.jsp or www.alldatacollision.com.)

During the installation, the part will be clamped in place — utilizing the EVO — and the measurements will be checked. Now, the quarter panel will be installed and clamped in place. With the structural parts installed and clamped in place, it's time to attach the bolt-on parts. We will install the rear door and check the gaps, starting with the right quarter panel to trunk lid gap. You will always start with a known, quality welded-on part and move on from there. Now, we will check the left quarter panel to trunk lid gap and the left rear door to left rear quarter panel gap. We will install the front door and line it up to the rear door and then the fender, headlamp and bumper fascia will be installed. Next, we will recheck all panel gaps to ensure there was no movement during the installation.

As we take a closer look, we notice some issues with the alignment and flushness of the panels. We grab a couple of our trusty dead blow rubber hammers to gently massage some areas of the parts into alignment and flushness, without causing any damage. We have all seen this issue before; The panel lines up correctly, but the lower edge or top of the door is bent inward or the top of the door is outward, and we use our knee to help with the adjustment. These adjustments cannot be made without this trial fitting procedure. Now that we have checked all the panel alignments, we are ready to weld the structural panels in place. Had you tacked these parts in place before trial fitting, you would have had significantly more work (and time) to correct alignment issues.

The first step to any welding operation is to make some practice welds and then destructively test them. Remember to make all the practice welds on the same material used on the vehicle. These scrap pieces can be obtained from the damaged parts or from unused replacement sections. You must also ensure weld quality by making test weld samples using the same type of welds recommended in the procedure, such as weld-bonding, STRSW, GMA/MIG plug, fillet or butt joint (with or without insert) welds. If using GMA/MIG welds, ensure that you practice in all the positions you will use on the vehicle, such as vertical, horizontal, overhead and flat, to ensure proper weld settings and penetration. After making practice welds, you will need to destructively test them, but do not throw them away. Write the Repair Order (RO) number on them and customer's name and take a photograph for the file. The destructively tested weld samples should be placed in a box and saved. If there is ever a question as to the quality of the welds, you will have photos of the destructively tested welds as well as the weld samples themselves. Doing this will help protect you from liability issues.

Now, you are ready to weld the panels into place. Start welding all the accessible flanges and sectioning areas; remember to use heat management procedures such as skip and stitch welds. After welding all accessible flanges, now disassemble the bolt-on parts that are obstructing the remaining flanges. After welding, dress the welds; this should be easy if you performed proper welding procedures. After dressing the welds, reassemble the bolt-on parts and recheck the alignment. Have the shop foreman check your work and sign off on it. Doing this will ensure that once the vehicle is ready for reassembly, there will be no surprises and the reassembly technician can be efficient.

Hopefully, this article has brought to your attention the importance of trial fitting and proper welding to maximize efficiency and ensure that the vehicle is restored to its pre-loss condition by following the OEM repair procedures.

Feel free to contact us at any time if you have any questions.

Larry Montanez is a former I-CAR instructor and is co-owner of P&L Consultants with Peter Pratti Jr. P&L Consultants work with collision repair shops on estimating, production and proper repair procedures. P&L conducts repair workshops on MIG & resistance welding, measuring for estimating and advanced estimating skills. P&L also conducts investigations for insurers and repair shops for improper repairs. P&L can be reached by contacting Larry at (718) 891-4018 or larrygoju@aol.com.

Jeff Lange, PE is president of Lange Technical Services, Ltd. of Deer Park, N.Y. (www.LangeTech.net). Jeff is a licensed New York State professional engineer who specializes in investigating vehicle and component failures. Lange Technical Services, Ltd. is an investigative engineering firm performing forensic vehicle examinations and analysis for accident reconstruction, products liability and insurance issues. Jeff can be reached at 631-667-6128 or by e-mail at Jeff.Lange@LangeTech.net.