Tech Updates

Sliding Pins and Bolts for Disc Brakes

For standardization reasons, reducing the number of spare parts and simplifying the handling of spare parts, Haldex changed the sliding pin and bolt design on its ModulX disc brake.

The modification to the sliding pin is internal and is basically a change in machining concentration to where the bolt head flange meets the sliding pin edge (as shown in Figures 1 and 2). There is no effect on other components. The modified sliding pin is asymmetric, but it is not possible to fit the pin and bolt incorrectly since the bolt can only be entered into the pin from one direction.

To meet the changed sliding pin mechanism, the attachment bolt is modified in design. The most noticeable change is a greater flange on the new bolt head.

The old bolt head (Figure 1) is tightened to 162 ft.-lbs. and the new bolt (Figure 2) is tightened to 206 ft.-lbs.

The new sliding pin cannot be used with the old bolt and vice versa.

Impact vs. Chrome Sockets

Chrome hand sockets and impact sockets have many differences that go beyond just appearance, according to Snap-on Tools, and each is designed and manufactured for specific applications.

For instance, a technician should never use a chrome hand socket on an impact gun – only use impact sockets. The impact socket has thick walls and is finished in a black phosphate or black oxide finish. Impact sockets also have a cross hole in the handle end for use with a retaining pin and ring or locking pin anvil to allow the socket to be securely attached to the square drive of an impact gun.

Power sockets, designed for use with power nut runners, multi-spindle machines and angle head nut drivers, may cause some confusion since they are offered in a black finish. But, Snap-on notes, they are stamped “WARNING: NON-IMPACT.” Power sockets are heat treated to a higher hardness than either impact or hand sockets. According to Snap-on, this high hardness, combined with thick socket walls, produces a strong, wear-resistant socket. This socket is suited for assembly-line work where it is not subjected to high-impact loads.

Hand sockets have a thin wall which allows for clearance in general applications where hand torquing is used. Hand sockets, except for those intended for industrial use, are chrome plated. Although hand sockets and power sockets can fit the impact wrench, they are not the same and must not be used on impact tools, Snap-on warns.

One difference you can’t see between these two types of sockets has to do with the way each has been heat treated and/or the composition of the metal used.

The impact socket made out of medium carbon alloy steel is heat treated to a low hardness range which has been optimized for impact use. This means that under heavy, continuous use, an impact socket will withstand the impact blows and will wear rather than break.

Hand sockets are made of medium carbon alloy steel that is heat treated to a hardness range commensurate with their size and configuration. Hand sockets are heat treated to a comparatively higher hardness for high strength and more wear resistance than impact sockets. But, they are made to sustain hand applied torque applications only.

Using only impact sockets on impact wrenches reduces the risk of injury, delays and damaged work. It’s relatively easy to spot a hand socket that’s been misused on an impact wrench, Snap-on says. Check the square drive end for signs of damage and distortion. Cracks and other damage often will appear around the wrench end as well.

Improperly using hand sockets on impact tools may be hazardous as they may crack. By knowing the difference between the various types of sockets and using them appropriately, you will be able to ensure a safer and more efficient work environment.

Replace damaged vac valves

According to Donaldson, the Vacuator Valve, standard on the majority of its air cleaners, is an important part of the functionality of the air cleaner during the pre-cleaning stage.

If the VacValve is cracked, torn, remains open or is missing, dust particles that normally are expelled can deposit themselves onto the filter and will shorten air filter service life. If the valve is cracked, torn, remains open or is missing, replace it.

For proper operation, the VacValve should be located at the lowest point on the air cleaner or with the dust cup pointing down.

Safety recalls

The National Highway Traffic Safety Administration (NHTSA) has issued the following recalls:

Nissan Diesel is recalling certain model year 1999-2010 UD3300 vehicles. These vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard No. 121, “Air Brake Systems.” The brake actuation and release timing of the air-brake system on these vehicles may not perform correctly. Operation of a vehicle with incorrect air brake apply/release timing may result in reduced braking performance without warning to the vehicle operator, which could result in a vehicle crash. The air brake line will be modified.

Additionally, these vehicles have insufficient air tank reserve capacity which may result in insufficient air supply to properly operate the brakes during repetitive brake applications. This may result in reduced braking performance which could result in a vehicle crash without prior warning to the vehicle operator. The air reservoir tank volume will be increased to meet FMVSS 121 requirements.

Navistar is recalling certain model year 2003 and 2004 IC Bus CE model commercial buses manufactured between January 3, 2003, and April 5, 2004. There may be chaffing between the battery and/or the engine ECM clean power cables and the parking brake cable, which may result in an electrical short. An electrical short may cause a fire without warning, which can result in property damage, personal injury or death. Inspect the battery and ECM clean power cables, repair if necessary and reroute them away from the parking brake cable.

Nissan Diesel is recalling certain model year 2007 and 2008 UD3300 vehicles that were modified by installing dual steering controls for use as street sweepers. These vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard No. 121, “Air Brake Systems.” Brake recertification was not performed on these vehicles during modification of the dual steering system. Operation of a vehicle with incorrect air brake apply/release timing may result in reduced braking performance which could result in a vehicle crash without prior warning to the vehicle operator. Dealers will inspect and replace the necessary components free of charge.