Large truck repairs call attention to the need for using OEM repair procedures

(Photo courtesy of GM) The 2017 light-duty and heavy-duty Silverados structurally are quite similar, but significant differences arise when it’s time to perform complex repairs life front rail sectioning

Potentially. That’s the worry of many automakers looking into a future where many younger consumers (especially in the United States) aren’t as focused on automobile ownership. They’re very concerned that someday, should consumers no longer be able to count on having their vehicles repaired properly, they’ll have even more reason to eschew automobile ownership. Toss into this potential maelstrom another trend: With vehicle designs growing in sophistication, requiring electronic checks to ensure complex automotive systems and sensors are working as intended, shops have even more reason to be turning to OEM instructions for every repair.

Translation: The industry probably could use a kick in the pants to change its philosophy on repair steps. Consider this article such a kick—or better yet a nudge. Here’s a look at critical differences in repair steps for subsets of the same popular vehicle models, specifically light-duty and heavy-duty trucks. Miss these details, and you’ll end up with an unacceptable and potentially unsafe repair that harms motorists, your shop and the industry all at the same time.

Silverado solution

The two sets of steps here detail full-frame sectioning on light- and heavy-duty versions of the 2016-2017 Chevrolet Silverado. The goal here is to note the similarities and the differences.

Note: Both repairs begin with recommendations to refer to GM’s documents on Approved Equipment for Collision Repair Warning and Collision Sectioning Warning.

Front full frame sectioning (Light Duty)

Removal Procedure

If damage permits a pre-sleeved replacement front frame service section has been developed as a cost-effective alternative to complete frame replacement.

This procedure is for the light duty pick-up front frame section, the utility front frame section is similar.

Note: Perform all of the steps on both of the rails for complete module replacement.

1. Disable the SIR system. Refer to SIR Disabling and Enabling documentation.

2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection (L83, L86, LV1, LV3) Battery Negative Cable Disconnection and Connection (L96, LC8, LML) documentation.

3. Remove all related panels and components.

4. Locate and mark the sectioning location by using at least two of the measurements below for each frame rail:

• Top of the frame rail edge rearward 420 mm (16 1/2 in.) (with bumper bracket removed)
• Bottom of the frame rail edge rearward 387 mm (15 3/16 in.) (with bumper bracket removed)
• Front edge of the gauge hole forward 22 mm (7/8 in.)
• Center of the gauge hole forward 33 mm (1 1/4 in.)
• Rear edge of the gauge hole forward 47 mm (1 7/8 in)

Note: Line up the masking tape with the tape edge facing the front of the vehicle on the sectioning location.

5. Apply masking tape completely around the frame rail next to the sectioning location as shown. Note that the tape edge facing the front of the vehicle is the proper cut location.

6. Cut each frame rail at the front edge of the tape line using a reciprocating saw or equivalent, as shown.

7. Remove the damaged frame section.

Installation Procedure

1. Grind the existing frame rail seam to taper seam at a 45 degree angle.

2. Prepare all of the attaching surfaces as necessary.

3. Apply the weld-thru primer to all of the welded surfaces.

4. Position the service frame section to the existing frame and clamp in place. Verify the frame measurements 3-dimensionally to ensure proper position of the service frame.

5. Continuous-weld the upper and lower horizontal joints through each corner.

6. Continuous-weld the inner and outer vertical joints from corner to corner.

7. Clean and prepare all of the welded surfaces.

8. Install all of the related panels and components.

9. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection (L83, L86, LV1, LV3) Battery Negative Cable Disconnection and Connection (L96, LC8, LML) documentation.

10. Enable the SIR system. Refer to SIR Disabling and Enabling documentation.

(Photo courtesy of GM) Instructions for the 2013 heavy-duty Silverado doesn’t feature UHSS recommendation.

Front full frame sectioning (Heavy Duty)

Removal Procedure

If damage permits a pre-sleeved replacement front frame service section has been developed as a cost-effective alternative to complete frame replacement.

This procedure is for the heavy-duty pick-up front frame service section.

Note: Perform all of the steps on both of the rails for complete module replacement.

1. Disable the SIR system. Refer to SIR Disabling and Enabling documentation.

2. Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection (L83, L86, LV1, LV3) Battery Negative Cable Disconnection and Connection (L96, LC8, LML) documentation.

3. Remove all of the related panels and components.

Note: Perform the following steps on both of the rails for complete module replacement.

4. Locate and mark the sectioning location by using at least 2 of the measurements below for each frame rail:

• Top of the frame rail edge rearward approximately 550 mm (with bumper bracket removed)
• Front edge of the gauge hole rearward approximately 5 mm
• Back edge of the lower control arm crossmember, rearward approximately 20 mm
• Approximately 50 mm rearward of shock tower bracket
• Approximately 55 mm rearward of shock tower bracket (inboard side rail)

Note: Line up the masking tape with the tape edge facing the front of the vehicle on the sectioning location.

5. Apply masking tape completely around the frame rail next to the sectioning location as shown. Note that the tape edge facing the front of the vehicle is the proper cut location.

6. Using a reciprocating saw or equivalent cut each frame rail approximately 5 mm forward of the front edge of the tape line. This will allow for final trimming of each rail rearward to the proper sectioning location.

7. Remove the damaged frame section.

Installation Procedure

1. Grind the existing frame rail (at the proper sectioning location) at a 45 degree angle.

2. Prepare all of the attaching surfaces as necessary.

3. Apply the weld-thru primer to all of the welded surfaces.

4. Position the service frame section to the existing frame and clamp in place. Verify the frame measurements 3-dimensionally to ensure proper position of the service frame.

5. Continuous-weld the upper and lower horizontal joints through each corner.

6. Continuous-weld the inner and outer vertical joints from corner to corner.

7. Clean and prepare all of the welded surfaces.

8. Apply sealers and anti-corrosion materials to the repair area, as necessary. Refer to Anti-Corrosion Treatment and Repair.

9. Paint the repair area. Refer to Basecoat/Clearcoat Paint Systems.

10. Install all of the related panels and components.

11. Connect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection (L83, L86, LV1, LV3) Battery Negative Cable Disconnection and Connection (L96, LC8, LML) documentation.

12. Enable the SIR system. Refer to SIR Disabling and Enabling documentation.

(Photo courtesy of GM) Just one year later, the 2014 heavy-duty Silverado received in-depth instructions for handling its UHSS parts. Repairing this Silverado using only experiences picked up from repairs of earlier models could be a disaster for a customer.

Catch what’s going on here? The instructions for front end sectioning of both the light-and heavy-duty versions of the 2016-2017 Silverado are nearly identical, except for the specific area where the sectioning is performed. The heavy-duty model receives this operation a bit further inward.

But this difference is critical. Sectioning is still a controversial repair procedure because of its possible effect on the functioning of critical safety systems in the event of a future collision. Consider the all the possible effects of sectioning in the wrong area because a shop didn’t refer to the proper documentation.

With the Silverado this is a potentially easy, though totally avoidable, mistake to make. Both versions of the Silverado feature roughly the same dimensions. The major differences are in powertrains and transmissions. But these differences dramatically affect how the vehicle reacts in a collision, hence critical differences in repair instructions.

The difference a year makes

Some shops will look at this example and note that GM has provided instructions for repairing both versions of the Silverado using similar sectioning dimensions for more than several years. But this factor actually creates additional issues since these similarities can help mask other significant differences, such as repair recommendations that can occur over the course of just one year.

For example, note the guidelines for repairing Ultra High Strength Steel in the 2014-2015 heavy-duty Silverado:

This type of steel normally has a tensile strength of 780 MPa, or greater.

This includes the common steel names of

• Ultra High Strength Dual Phase Steel (DPX)
• Martensitic Steel (M)
• Boron/Press Hardened Steel (B)
• Multi-Phase Steel (MP)
• TRIP Steel (TR)

General Motors recommends the following when repairing or replacing this type of steel during collision repair.

Note:

• Repair of this type of steel is not recommended.
• This type of steel should be replaced only, at factory joints. Sectioning or partial replacement is not recommended.
• The use of heat to repair damage is not recommended for this type of steel.
• Stitch Welding is not recommended for this type of steel (unless replacing a factory installed stitch weld).
• This type of steel should not be used as a weld plate for reinforcing the sectioning location.

Recommended Repairs

• Squeeze Resistance Spot Welding can be used to replace factory spot welds, where applicable.
• MIG plug welding can be used to replace factory spot welds.
• MIG Brazing can be used to replace factory spot welds.

Now, review the UHSS recommendations for the 2013 heavy-duty Silverado.

Nothing.

Repairing a 2014 model using experiences associated with an earlier model could prove disastrous. Considering the same “general” repair instructions can be repeated for multiple model-years, it’s even easier to lose count of vital new information.

Moving forward

This is the repair tale that heavy-duty trucks deliver to repairers. OEM instructions matter, and they need to be a part of every repair. Ignoring them not only puts customers and the shops at risk now, they set much of the market down a path where it may not get an opportunity to recover.

That’s one harsh lesson repairers can’t afford to learn.