NHTSA Office of Defects Investigation
Preliminary Evaluation PE10-042: Failing 5th wheel attachment bolts
- Closed
NHTSA's Office of Defects Investigation opened Preliminary Evaluation PE10-042 on November 4, 2010 and closed it on April 27, 2011. NHTSA's investigations file lists 5 Mack models for it and links recall 11V-209 to it.
Updated daily from NHTSA's investigations file
Key facts
- NHTSA number
- PE10-042 (also written PE10042)
- Investigation type
- Preliminary Evaluation The first stage of most defect investigations: NHTSA's Office of Defects Investigation gathers basic information about a possible safety defect, including from the manufacturer.
- Status
- Closed April 27, 2011
- Opened
- Closed
- Vehicle or equipment manufacturer
- Mack Trucks, Inc.
- Component
- Trailer Hitches — Fifth Wheel Assembly
- Recall linked by NHTSA
- 11V-209: FIFTH WHEEL MOUNTING BOLTS, reported
- Vehicles and equipment
- 5 Mack models, including the CXU and CXU612
NHTSA's summary
As NHTSA's Office of Defects Investigation wrote it for Preliminary Evaluation PE10-042.
On October 3rd 2010 the Office of Defects Investigation (ODI) received two complaints on 2009 - 2010 Mack CXU612 and CXU trucks for failing bolts that clamp the 5th wheel to the frame of the truck. On January 19, 2011 ODI opened this Preliminary Evaluation.
During the course of the investigation ODI took possession of fasteners from the field.
These fasteners, taken off subject complaint vehicles, exhibited 'hourglass like stretching' indicating plastic deformation.
This same source supplied ODI with new fasteners (for the subject vehicle) that were recently purchased and never used.
The bolts supplied by the manufacturer are M16 x 2 Class 10.9 bolts.
Per SAE J1199, these bolts should have a proof load 130 kN (~29,000 lbf) and tensile strength of 163 kN (~36,600 lbf).
These bolts are not designed to be torque to yield.
ODI took possession of these field samples and sent them to (VRTC) Vehicle Research and Testing Center for testing.
Some of the new and used fasteners from the field were tested to the SAE J1199 standard and all passed.
Other tests at VRTC indicated that the stretched bolts were likely the result of over torque during installation or maintenance.
VRTC tested other methods to pre-tension the bolts and found that load indicating washers and turn-of-the-nut method both gave better clamping load control than a torque wrench.
In February 2011 Mack started to perform field inspections associated with this investigation in an attempt to understand the cause of the bolt failures.
During these inspections, Mack discovered that there was an interference with the bolts used to secure the fifth wheel to the frame.
This interference can prevent the bolts from being torqued to specification.
If this occurs, the bolt(s) may fail and in extreme cases may result in the fifth wheel coming loose causing the trainer to separate from the tractor.
Mack has issued a voluntary Safety Recall 11V-209 for (failure of fifth wheel mounting bolts). However, claims in the field suggest the manufactured supplied fasteners are inferior and stretch regardless of interference.
ODI will continue to monitor this issue and follow the completion progress.
If failures continue, ODI may open another investigation to investigate future failures.
Mack Truck's recall action resolves the issues raised by this investigation and, therefore, this investigation is closed.
Vehicles and equipment listed for this investigation
NHTSA's investigations file lists these vehicles and equipment for Preliminary Evaluation PE10-042. A listed model year means only that an investigation names it; it says nothing about any particular vehicle. Model years with a try.vin recall page link to that page's NHTSA investigations section.
Mack
All Mack recallsWhat an NHTSA investigation is
NHTSA's Office of Defects Investigation (ODI) looks into possible safety defects in vehicles and equipment, often after owner complaints. An investigation usually starts as a Preliminary Evaluation, or as a Recall Query when it concerns whether an existing recall covers the right vehicles or fixes the problem, and ODI can upgrade it to a more detailed Engineering Analysis. A Defect Petition asks NHTSA to open an investigation, and Audit and Equipment Queries are administrative investigations into whether companies complied with federal vehicle safety requirements, such as reporting, recall and certification rules.
An open investigation is not a finding that a safety defect exists, and NHTSA can close one without a recall.
To see whether a specific vehicle has an open recall, enter its VIN at nhtsa.gov/recalls.
Free VIN check: decode a VIN to see its year, make and model.
Sources
NHTSA's investigation record for PE10-042
Investigation details come from NHTSA's investigations file, which try.vin imports once a day. The investigation types are described from the U.S. Department of Transportation Inspector General's May 2023 report on NHTSA's Office of Defects Investigation, NHTSA's petition rules (49 CFR Parts 552 and 557) and NHTSA's Office of Defects Investigation procedures. How try.vin reads NHTSA investigations.