According to this press release Navistar has been forced to recall over 5600 buses because hex flange lock nuts in the steering and suspension systems were not heat treated properly. Once again it is proven that heat treating is a crucial component of almost all types of manufacturing.

“Navistar informed the National Highway Traffic Safety Administration (NHTSA) about a recall for over 5,600 of its newest IC buses. Used to transport kids to school and people to work, these vehicles are at risk because of issues with their steering and suspension systems. IC Bus manufactures internationally famous American school buses. But these yellow units meant for transporting children aren’t the only ones you’ll find on the road. Many government bodies and state institutions use the same buses for different activities. Similarly, private companies that need to move their workforce daily might have them in their fleets. That’s why this recall is so important.

According to NHTSA’s latest safety recall campaign identifiable with the 22V870 code, Navistar’s IC Bus will recall 5,645 units for critical issues with their steering and suspension. They discovered that the hex flange lock nuts may break. These are used in the suspension and steering joints. The company blames the heat treatment applied to these parts. If the hex flange lock nuts fail, they can cause a loss of tension which leads to steering instability. The risk of crash increases as a result.

When the hex flange lock nuts are manufactured properly, they are preferred over the hex lock nuts because they can be installed faster, there’s no need for washers, and serration is possible on a larger bearing surface which translates into better tightening strength and helps with speeding up the assembly line’s output. The recall involves the following bus models – CE, EV, and RE. They all are 2023 model-year units.”

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