Suspension System Diagnosis and Repair - B Flashcards
1
Q
Describe heavy-duty front axles.
A
Heavy duty front axles are forged solid I-beams. - The axle is mounted to the leaf springs and retained with U-bolts.
2
Q
How would you inspect an axle?
A
- Perform a thorough visual inspection to identify looseness and shifted or broken parts. - Inspect the U-bolts and shims for proper torque and placement. - Measure the front wheel set back on both wheels and compare because a difference in measurement could be caused by a bent axle, or worn, misaligned components (i.e., spring eye bushings) - Check the axle for twist using a machinist’s protractor. - Check the axle for twist using a machinist’s protractor. - If the front axle must be removed, pay particular attention to spacers and castor shim placement. - Be sure to mark the front of the axle to ensure proper placement when reinstalled. - Always replace the U-bolts. U-bolt threads stretch during initial installation and scale and rust buildup may prevent improper pull-up torque and insufficient clamping force.
3
Q
Describe kingpins and their function.
A
- Some OEMs refer to the kingpin as a knuckle pin. - Kingpins may be a straight or tapered design. - Kingpins connect the I-beam to the steering knuckle and act as pivots to turn the front wheels.
4
Q
What could a loose kingpin or kingpin bearing cause?
A
Could cause a shimmy with slight vibrations. - A dial indicator is used to measure vertical play, upper and lower bushing free play, and upper and lower bushing torque deflection in the knuckle.
5
Q
How would you adjust vertical end play?
A
Is adjusted by adding or removing shims to obtain the manufacturer’s clearance specification. - If the bushing free play measurements are out of spec, the bushings and kingpin will need to be replaced.
6
Q
How do you grease a front axle kingpin?
A
- Place a jack under the front axle and raise the vehicle to unload the suspensions. - Grease the upper bushing until grease appears between the steering knuckle and the top of the axle eye. - Grease the lower bushing and continue greasing until grease begins to leak out through the pivot bearing. - This shows a thorough distribution of the grease.
7
Q
What should you do when replacing the kingpins?
A
- Remove the upper and lower knuckle caps to access the kingpins. - Remove the draw key nut and drive out the draw key. - Then press out the kingpin from the knuckle. - Prior to assembly, check the axle eye bore for wear.
8
Q
What does the draw key do?
A
The draw key keeps the kingpin aligned and tight in the axle bore. - When reassembling the assembly, torque the draw key nut to the manufacturer’s specification. - The draw key torque should also be checked at every preventive maintenance inspection.
9
Q
What happens when a vehicle hits a bump?
A
The wheel and suspension move upward in relation to the chassis. - This causes jounce and rebound.
10
Q
What do shock absorbers do?
A
Shock absorbers dampen or control spring action from jounce and rebound, reduce body sway, and improve directional stability and driver comfort.
11
Q
What happens with worn-out shock absorbers?
A
Worn out shock absorbers, will allow the front end to bounce, causing the steering wheel to shake for a few seconds. - The piston sheild often gets bent or damaged and will scrape against the shock absorber when the suspension moves up and down. - Shock absorbers stop spring oscillation and are still needed on air spring suspensions.
12
Q
How should you inspect shock absorbers/
A
Should be inspected for loose mounting bolts and worn mounting bushings. - If these components are loose, rattling noise is evident, and replacement of bushings and bolts is necessary. - In some shock absorbers, the bushing is permanently mounted in the shock, and the complete unit must be replaced if the bushing is worn.
13
Q
What is the result of worn mounting bushings?
A
The shock absorber will not provide proper spring control, and rattling will occur when driving over road irregularities.
14
Q
What happens if you find oil leakage in shock absorbers when inspecting?
A
A slight oil film on the lower oil chamber is acceptable. - Any indication of oil dripping is not acceptable, and unit replacement is necessary.
15
Q
What should you visually inspect shock absorbers for?
A
For a bent condition and severe dents or punctures. - When any of these conditions are present, unit replacement is required.
16
Q
How should you manually test shock absorbers?
A
When this test is performed, disconnect the lower end of the shock and move the shock up and down as rapidly as possible. - A satisfactory shock absorber should offer a strong, steady resistance to movement on the entire compression and rebound strokes. - The amount of resistance may be different on the compression stroke compare with the rebound stroke. - If a loss of resistance is experienced during either stroke, shock replacement is essential.
17
Q
What should you do if you have a defective shock absorber that has internal clunking, clicking, and squawking noises, or binding conditions?
A
Shock absorber replacement is necessary. It is advisable to replace shock absorbers in pairs.
18
Q
What is a leaf spring?
A
A leaf spring is a spring assembly where the individual leaves are the same width for the whole length of the assembly.
19
Q
What are parabolic springs?
A
Parabolic springs are assemblies where the leaf width is usually greater at the center of the spring, and the width decreases toward the outer end of the spring.
20
Q
How is a taperleaf spring classified?
A
A taperleaf spring is classified as a parabolic spring since the leaves are thicker in the center, and the thickness decreases toward the end of the leaf.
21
Q
What are the steps to take when inspecting the leaf/parabolic spring assemblies?
A
- Look for broken or shifting leaves in the spring pack. - Inspect the front and rear shackle spring pins and bushings for wear. - Inspect the U-bolts, spring seats, and top plates for looseness or wear.
22
Q
The suspension system should be inspected periodically to ensure vehicle safety as part of a regular maintenance schedule recommended by the truck manufacturer or owner. What components should you check?
A
_Inspect the tires for excessive tread wear. -Check the torque on the wheel nuts, and inspect the wheel rims for damage. - On rear suspension systems, inspect all torque rods for damage or a bent condition. Inspect all torque rod bushings for looseness, wear, and deterioration. - Inspect all spring shackles, bushings, and brackets for looseness. A pry bar may be used to pry downward on the outer end of the spring to check for looseness in the shackles and bushings. - Inspect all spring U-bolts for damage and check the torque on the U-bolt nuts. - Inspect the springs for broken leaves, damaged clamps, broken center bolts, and a sagged condition. - Inspect all equalizer components for wear.
23
Q
Where should you be sure each side of the drive axle housing is position?
A
On the same location on each spring. A broken center bolt may allow the drive axle to slide backward on the spring.
24
Q
What can and will not break the spring center bolt?
A
Loose spring shackles will not break the spring center bolt. Loose front spring U-bolts can break the spring center bolt or leaves between the U-bolts.
25
What can a broken leaf spring center bolt cause?
A broken leaf spring center bolt can cause axle shifting leading to premature toe-like tire wear and steering pull. -If the spring assembly is replaced, always replace the U-bolts.
26
What happens to U-bolts threads during initial installation?
U-bolt threads stretch during initial installation and scale and rust buildup may prevent improper pull-up torque and insufficient clamping force.
27
If a defective spring assembly is identified, what should be considered?
- Whenever one spring leaf is broken, all of the other leaves in the assembly have been overloaded and running under increased stress. Consideration should be made to the age and condition of the other leaves prior to repair. - If one spring leaf is broken and the remaining leaves are deemed serviceable, it is acceptable to replace only the broken leaf, however it is advisable to replace the same leaf in the other spring pack on threat axle to ensure both spring assemblies remain matched regarding load carrying capacity, rate of deflection, and ride height characteristics. - If two or more leaves are broken in the spring pack, it is recommended that the entire spring assembly be replaced. - If the spring assembly on one side of the vehicle is being replaced, it is advisable to replace both spring assemblies across that axle.
28
What do torque rods, radius rods/arms, transverse torque rods, and torque leaves do?
Provide braking force absorption and allow for driveline angle adjustment and axle alignment.
29
What do tandem axle suspensions often have?
Four multi-leaf springs and four torque rods.
30
Where is an equalizer hanger (center hanger) mounted?
Is mounted to the frame between the front and rear springs on each side of the tractor. - The springs ride on an equalizer pivot beam mounted on a sleeve in the equalizer bracket.
31
What may be substituted for rear shock absorbers?
Torque rods. - Four to six torque rods may be used on spring suspensions for suspension alignment. - Torque arms are either adjustable or fixed-length design.
32
How would you make rear axle alignment adjustment on a spring suspension with adjustable torque rods?
Can be made by rotating one end of the torque rod in or out of the threaded sleeve.
33
How do fixed-length torque arms help to align the rear axle?
Fixed length torque arms use shims between the front of the torque rod and spring hanger bracket to align the rear axle.
34
How do some manufacturers achieve axle alignment?
Utilize a multi-leaf spring pack equipped with a torque leaf. - In this case, an eccentric bushing at the torque leaf is rotated to achieve alignment.
35
How would you inspect torsion bars?
Torsion bars are the same length but are usually not interchangeable left to right. - As long as a torsion bar is not cracked or broken, it can be adjusted at the crank assembly to level the vehicle. - You never heat or bend torsion bars or torque arms.
36
What will premature suspension bushing wear cause?
Will cause noisy operation, directional instablilty and excessive wear to adjacent suspension components.
37
How would you inspect the torque arm/leaf bushings and pins for wear?
Inspect the torque arm/leaf bushings and pins for wear, cracking, and shifting. - In addition, you should check the mounting bolts and shim packs on units utilizing this mounting method. - When bushings are replaced, be sure the suspension is in a neutral state. - A bushing not relaxed during assembly can cause a binding condition leaving a vehicle off-level.
38
What do equalizing beam suspension do?
Equalizing beam suspension lowers the center of gravity of the axle load.
39
What are the two types of equalizing beam suspensions ?
The two types of equalizing beam suspensions are leaf spring type and rubber load cushion type. - In a leaf spring-type suspension, the front of the leaf springs assembly utilizes a spring pin to mount it to the front hanger. - The rear of the spring has no rigid mount allowing for forward and rearward movement to compensate for spring deflection. - The spring assembly mounts to a saddle with either U-bolts or straight bolts.
40
What is the function of tandem rear-axle suspension systems.
Tandem rear-axle suspension systems have equalizer beams on each side of the suspension. - The equalizer beams incorporate bushings at each end and in the center of the beam. - The equalizer beams are attached to the fron and rear axle housings and the spring saddle. - A cross tube is mounted between the two equalizer beams. - You can service walking (equalizing) beam center and end bushings on the vehicle using a special OEM tool. Multi-leaf springs are mounted on saddles above the equalizer beams.
41
How should you inspect walking beam suspensions?
The technician should look for beam bushing wear, spring stack shifting, loose mounting hardware, spring hanger or rubber cushion wear, and torque arms and bushings. - In addition, inspect the cross tube for wear or damage. - Wear in the cross tube may indicate worn equalizer beam bushings.
42
What are the recommendations if a defective spring assembly is identified.
- Whenever one spring leaf is broken, all of the other leaves in the assembly have been overloaded and running under increased stress. Consideration should be made to the age and condition of the other leaves prior to repair. - If the spring assembly on one side of the vehicle is being replaced, it is advisable to replace both spring assemblies across that axle.
43
What would you do in a visual inspection of the pneumatic (air) system?
Checks are to be performed for incomplete, binding, or improperly adjusted linkages; valves mounted in the wrong position; air line leakage, fraying, cracking, chafing, or improper positioning; or anything that could lead to future failure.
44
What is the most effective means of locating small leaks?
Soap-and-water solution sprayed onto all air system components; observe bubbles as an indicator of the leak source. - Test system to determine if valves are of the time delay type, - Install a suitable gauge to determine the proper delivery of air pressure.
45
What might be the problem with vehicles that keep swaying back and forth or side to side?
Can have worn-out shock absorbers, the wrong type of air valves (none or too much time delay), or insufficient air supply.
46
What will a visual inspection determine in regard to the air springs and related mounting hardware?
Visual inspection will determine if the air springs and related mounting hardware are mounted in proper position so as to facilitate proper movement and rigidity. - Suspension arms must be checked for bushing wear and movement. - Check manufacturer's specifications for each individual system type.
47
What should air springs (bags) be checked for?
For possible damage, such as cuts, exposed cords, cracking, or wear due to misalignment. - Replacement of air bags is recommended, as the cost of the new unit is economical and repair is not suggested.
48
When should the pressure protection valve be inspected to the valve closes?
If the air pressure drops to less than 70 psi (482.65kPa) to protect the air brake system from the low air pressure. - Some systems may incorporate a pressure regulator valve. - If equipped, the pressure regulator should be checked for proper mounting, air leakage, and proper operation.
49
What should leveling valves be checked for?
For binding, air leakage, and proper adjustment.
50
When are non-powered lift axles installed?
Ahead of or behind the driving tandem axles on a straight truck or tractor. - If it is ahead of the tandem, a lift axle is called a "pusher." - If is behind, it is a "tag." - Such axles can also be installed ahead of or behind a trailer's tandem. - In addition, a lift axle is occasionally applied to a sing-rear-axle straight truck.
51
What should inspection of the lift axle assembly include?
- Check all fasteners installed and bolts for proper torque specifications. Note: All fasteners torque specifications are given for dry fasteners with no additional lubrication required. - Inspect all wheel lug nuts tightened to recommended torque specifications. - Raise and lower the assembly and inspect the air control system for leaks and proper operation. - As the suspension is raised and lowered, inspect for any interference between the auxiliary suspension and any truck components. - Ensure that the brakes and slack adjusters are properly adjusted, and the wheels free to rotate. - Check the wheel hubs for proper oil level and are filled with the manufacturer's specified lubricant. - Check that the toe-in adjustment is set properly (1/8 +/ - 1/16 measured at the tire centers).
52
What must happen with the vehicle unloaded?
The auxiliary axle's ride springs must be limited to a maximum of 20 psi to avoid improper weight distribution or component damage.
53
To determine needed adjustments or repairs when measuring front and rear vehicle ride heights, what manufacturers specifications should you address the?
\_ The type or model of the suspension; for example, spring or air type. _ The load rating of the suspension. \_The point(s) of measurement. \_Measurement specifications. \_System air pressure and supply (if air type). \_Tools needed to perform measurements. \_How measurement will be performed; for example, flat floor, load or no load or trailer attached, or brakes applied.
54
How should you always perform a height setting on an air spring system?
\_With proper air pressure and supply - air dump valve closed and the system air supply valve applying air (air going into the system) - for accurate results. \_Perform a road test and reconfirm ride height. \_Improper suspension ride height will cause driveline vibrations; accelerated U-joint wear; and changes in geometry to the center of gravity (load), steering, and braking systems.
55
How would you verify and diagnose vehicle suspension complaints?
\_Perform a visual inspection and road test of the vehicle to determine if the condition exists as reported.
56
If the ride of the vehicle is unusually harsh what should you do?
\_Test to confirm tire pressure and construction; that is ply design radial or bias, ply count in the tread and sidewall, width of tire and rim. \_Refer to manufacturer's specifications to confirm that the recommended type of suspension for the load carried is installed on the vehicle. \_Confirm that the suspension has not been modified; that is, new springs, increase or decrease in the spring rates. \_Confirm suspension height specifications. \_Determine if alignment is within specifications (especially caster). \_Check for binding or loose steering components. \_Measure steering box and column bearing preload specifications. \_Check shock absorber function. Check for correct mounting of components, bushings, rods, etc.
57
What can the problems be if rough ride characteristics are experienced?
\_Excessive positive caster, leaking or damaged shock absorbers, and loose or worn suspension components can cause rough ride characteristics. \_Improper wheel balance, worn kingpin bushings, a bent wheel mounting surface, or a shifted belt inside a tire can also cause rough ride characteristics.
58
Why do leaf spring suspensions require the use of U-bolts?
To hold the spring assembly in its proper location. \_Any movement between the spring and the housing can produce axle tracking problems and the possibility of shearing the spring center bolt and leaf breakage between the U-bolts. \_These U-bolts must be torqued to specification to produce the proper clamp load on the spring assembly to prevent any movement of the spring in relation to the axle housing.
59
What must you do when new U-bolts are installed?
\_They must be re-torqued after the first 1,000 miles of loaded operation and every 36,000 miles afterward. \_When tightening old U-bolts, ensure that no rust or thread damage is present by cleaning and inspecting the bolt and nut threads prior to performing the re-torque procedures.
60
What should happens when a tandem rear axle vehicle is loaded?
\_The load placed on each axle should be as balanced as possible.
61
What will a vehicle with an axle loading imbalance do?
A vehicle with an axle loading imbalance will place more stress on the driveline and axle assemblies and will produce more tire wear on the axle carrying the heavier load.
62
What can happen when the load placed on each axle varies by more than 500 lbs. (227 kg)?
\_Shims can be placed between the axle and spring of the axle with the least load. \_Many manufacturers have produced charts to guide the technician in selecting the appropriate shim to correct the imbalance.
63
What should you do when measuring the axle loading?
The fifth wheel should be placed in its normal operating location and the average load that the vehicle will be carrying should be place on the suspension. \_A leveled single or tandem axle scale should be used for axle measurement. \_If spring adjustments are required, the positioning of the axle may be altered and the drive pinion angles should be measured and adjusted if necessary to prevent the creation of any driveline vibration.
64
When will frame sway occur?
Frame sway occurs when one or both frame rails are bent inward or outward.
65
What are some causes of frame sway?
Collision damage, fire damage, snowplowing abuse, and using the truck for other than original design.
66
Frame sag occurs when the frame rails are bent downward in relation to the rail ends. What are some causes of this?
\_Excessive loads \_Uneven weight distribution \_Holes drilled in frame flanges \_Too many holes drilled in the frame web \_Holes drilled too close together in the frame web \_Welding on the frame \_Cutting holes in the frame with a torch \_Cutting notches in the frame rails \_Fire \_Collision damage \_Using the trick for other than original design
67
When does frame bow occur and what can cause buckle?
When one or both frame rails are bent upward in relation to the ends of the rails. Causes of buckle: \_collision, operating a dump truck with the bos up and loaded. \_snowplow operation \_unequal loading of the frame using the truck for other than designed intend \_fire
68
When do diamond-shaped frame occur?
Occurs when one frame rail is pushed rearward in relation to the opposite frame rail. _ Vehicle tracking is affected by this condition. \_Causes of diamond-shaped frame: collision, towing, or being towed with the chain attached to only one side of the truck frame.
69
When does frame twist occur?
Occurs when the end of one frame rail is bent upward or downward in relation to the opposite frame rail.
70
What are the causes of frame twist?
Collision damage, rollover, rough terrain operation, and uneven loading.
71
What causes frame buckling and mashing?
Is wrinkling of C-channel flanges that accompany different categories of frame damage.
72
How would you repair frame sway, sag, bow, diamond, or twist conditions?
Vehicles exhibiting these conditions should be taken to a frame shop having the equipment and expertise to perform the needed repairs. \_After a straightening job has been completed, the technician should check the repaired vehicle carefully. \_This check should include an inspection of each rail to make sure that there are no buckles or wrinkles. \_Rear housings or trailer axles must be set at a 90 degree angle to the center line of the chassis. \_The rear end should be checked to make sure that it is square with the chassis. \_Reinforcing sections should fit snugly in the old channels. \_Finally, a road test can help determine whether a frame was properly straightened.
73
Welding repairs on truck frames should be performed by a qualified welder. What is a possible exception?
The repair of minor cracks in the frame. \_When making such a repair on steel frames, the shielded arc method should be used because the heat generated during welding is localized and overheating is minimized. \_Additional advantages are that the finished weld can be ground flush and drilled as necessary.
74
What are the recommended methods for crack repair of steel frame members?
Recommended methods are: \_Shielded metal arc welding (SMAW) \_Gas metal arc welding (GTAW), also know as metal inert gas (TIG) \_Welding; or flux cored arc welding (FCAW)
75
How must reinforcements be made?
Reinforcements must be made with suitable channel stock. \_The reinforcements should be made of a material matching the yield strength of the frame. \_The length of reinforcement is dependent on the type of service the truck is used in and the frequency and severity of loading. \_Reinforcements should be bolted rather than welded to the frame rail, keeping the bolt pattern close to the neutral fiber.
76
Reinforcements may be installed on the outside or the inside of the frame side rail. How should they be installed?
\_When installing an inner frame reinforcement at a cross member, it will be necessary to alter the length of the cross member or replace the one-piece cross member with a multi-piece (bolted) cross member. \_Alteration of bolt hole locations in a multi-piece cross member may be required to suit the application.
77
Why must reinforcement plates be long enough to extend beyond the critical area?
So that the ends can be cut at a 45-degree angle instead of square across the frame section. \_If this is not possible because of obstructions, try to relieve any high-stress pressures by spreading the load over a curved section. \_Also avoid several holes in direct vertical alignment or holes too close together. \_A staggered bolt pattern with good spacing and sufficient edge distance is desirable.
78
Is cutting the frame behind the rear axle to alter the wheelbase is acceptable or unacceptable to most manufacturers?
It is acceptable. Consult the manufacturer regarding whether reinforcement is required when extending a frame in this manner.
79
What are most frames today assembled with?
Huck fasteners, bolts, and nuts. \_Others are riveted. Bolts always must be used when attaching a reinforcement. \_Rivets can be replaced by bolts when the frame is repaired and reinforced.
80
In bolted joints, how is the majority of the load transferred?
By the clamping force between the members of the joint.
81
Why must bolts be properly torqued?
To develop and maintain the desired clamping force. \_Loose or improperly torqued bolts can lead to failure of the joint. \_The bolts and nuts should be inspected periodically to ensure that proper torque is maintained.
82
What must Bolts and Huck fasteners always be replaced with?
By fasteners that meet OEM specifications. \_May be SAE Grade 5 body-bound (machined with an interference-fit shank), SAE Grade 5 or Grade 8.
83
Why is it poor practice to replace Grade 5 fasteners with Grade 8?
Because of the flex performance of each grade. \_Ensure that the nuts also meet OEM specification.
84
Why should you never consider replacing body-bound bolts with standard shank bolts?
Because the result will be excessive movement at the fastener. \_Body-bound bolts are machined with an interference shank designed to limit movement. \_Holes that are enlarged or irregularly worn may be reamed to accept the next larger bolt diameter.
85
If frame components are aluminum, what should be used?
Flange-head nuts and bolts, or hardened flat washers must be used next to the aluminum under both the bolt head and nut. \_If modification or repair requires the replacement of existing bolts with new bolts or bolts of greater length, the old nuts also should be replaced.-+
86
What are the careful consideration which should be given in the design of the vehicle?
The number, location, and sizes of frame bolt hole in the design of a vehicle. \_The number, location, and sizes of additional bolt holes installed to the frame subsequent to manufacture of the vehicle can adversely affect frame strength. \_The drilling of the frame side member presents no unusual difficulty. \_Standard high speed steel drills of good quality will usually serve, provided they are sharpened properly and not overheated during sharpening or use. \_Because drills almost always produce a fractionally oversize (over nominal size) hole, always finish a frame hole by using a taper reamer.
87
What are the general guidelines that should be followed when drilling holes in a heavy-duty chassis frame?
\_Never drill holes into the flange sections of the frame rails. \_Use existing holes whenever possible. \_Holes should be located as close to the center or neutral axis of the side member as possible. \_Maintain a minimum of 3/4 inch of material between holes. \_There should not be more than three holes located on a vertical line. \_Bolt holes should be no larger than is required for the size of the bolt being used. \_If reinforcements are used, avoid drilling holes closer from the ends of the reinforcement. \_Bolts must be checked periodically to ensure that the proper torque and clamping force are maintained. \_Holes are not permitted in the drop portion of the web of drop center rails. \_The center of the holes must not be closer than 1/2 inch for aluminum rails or 1 inch for steel rails to the top or bottom flange face or be less than 3 inches apart. \_Bolt holes must not be larger than those existing in the frame, such as for spring bracket bolts. \_On aluminum frame rails, chamfer both sides of all holes 0.02 inches by 45 degrees.
88
When you perform a visual inspection to evaluate the condition of frame hangers, brackets, cross members and fasteners, what should you look for?
\_Replace any cracked, bent, broken, or damaged components.
89
What are three common methods of attaching specialized equipment to the frame chasis?
Are bolts, U-bolt and clamp attachments, and welding. \_Bear in mind that anything you attach to a frame rail is going to significantly alter the frame dynamics.
90
When is bolting preferred for versatility and strength?
When the holes used for fasteners are in the least critical areas possible. \_This type of loading stretches the lower half of the section (produces tension) and compresses the upper half of the section (produces compression). \_If the side rail section was without holes, the highest concentrations of stress (tension and compression) would be in the lower and upper flanges of the rail.
91
When doing bolt attachments, where should the uppermost hole be located?
Should be located about one-third of the web depth up from the lower flange. \_Stress (tension) at the bottom of this hole would be approximately equal to the stress in the lower flange. \_Any hole located less than this distance (for example, a hole located nearer to the lower flange) will have significantly higher stress than will the flange.
92
What is the reason for the difference in stress among the holes?
Is that the upper hole is located closer to the neutral axis of the rail, or the area where the forces of tension and compression are lower.
93
What are the recommendations to be considered whenever equipment is to be bolted to the chassis frame?
\_Use existing holes where possible. When holes must be drilled, they should be located no closer to the top and bottom side rail flanges than the existing holes placed by the factory. \_Avoid drilling holes in any area of the side rail web except the central one-third area. (The web is the surface area between the flanges.) Depending on loading, the top or the bottom of the side rail can be the tension side. \_Before drilling holes in the side rails, obtain approval from the OEM regional service representative. \_In all cases, avoid drilling holes in the side rail flanges.
94
What are the least time-consuming and least expensive methods of attachment?
Clamping devices.
95
U-bolts avoid frame drilling. How is especially helpful?
When the vehicle is equipped with a heat-treated frame. \_But because U-bolts or clamps are not locked to the frame, there is the possibility of heavy equipment moving or being jarred out of place, especially if grease or oil is present on the frame rail. U-bolts and clamps cannot hold high-torque loads and can cause local stress concentrations.
96
What are guidelines to be considered when using U-bolts and clamps?
\_Care should be used to block (with spacers) the side rail channel to prevent collapse of the flanges when the U-bolts are tightened. Steel blocks are preferred because wood may contract and drop out. \_The blocks used to prevent collapse of the side rail flanges should not interfere with plumbing or wiring routed along the frame rails. In addition, the blocks should not be welded to the side rail flanges. \_Because U-bolts and clamping devices depend on friction and a maintained clamping force for attachment, some bolts should directly connect the attachment to the frame side rail web to prevent the attachment from slipping. \_Do not notch frame side rail flanges in order to "force" a U-bolt fit. If the side rail flanges are too wide, obtain a larger U-bolt or use another method of attachment.
97
Regarding direct welding, what should be avoided?
Direct welding of the side rail flanges and web should be avoided. \_To avoid direct welding, equipment brackets should be welded on a separate reinforcement, and the reinforcement should be bolted to the side rail. \_It is recommended that before any direct welding to the side rails is performed, the manufacturer be consulted. This step could keep the warranty in effect.
98
When should the operation of the fifth wheel be checked first?
While the tractor is connected to a trailer. \_The complete assembly should be washed and inspected for plate wear, cracks, damage, and loose or missing parts.
99
How should the fifth wheel operation be checked?
With a suitable lock tester for jaw or latch wear according to OEM service information. \_The mountain bolts and weld areas should also be checked for integrity. \_Any components showing wear or damage should be replaced.
100
What should happen with the fifth wheel, after all repairs are performed?
Fifth wheel operation should be rechecked with a suitable lock tester.
101
What should happen after all fifth wheel repairs are performed?
The fifth wheel plate should be lubricated with water-resistant, lithium-based grease. \_All moving parts should also be lubricated according to manufacturer recommendations. \_These checks should be performed after the first 1,000 miles (1,6000 km) and every 30,000 miles (50,000 km), afterward to ensure safe and secure operation.
102
How is a sliding fifth wheel designed?
Is designed to move forward or rearward on its mounting plate. \_This type of fifth wheel is mounted on tracks and locked in position. \_The locking mechanism may be released mechanically with a lever or by air pressure supplied to an air cylinder.
103
`How would you inspect the sliding fifth wheel?
\_Inspect the track and slider mechanisms for damaged or missing teeth and wear. \_The fifth wheel stop welds should be inspected to ensure weld integrity. \_Check the air cylinder (if equipped) for proper operation and air leakage. \_Inspect plunger operation and adjust if required. \_Lubricate all moving parts with a light, rust-resistant oil.
104
Where is the kingpin stub mounted?
Is mounted on the trailer upper coupler assembly. \_Most are welded to the upper coupler assembly but both bolt-on and removable fasteners are also used. \_Trailer kingpins should be periodically cleaned and inspected for wear, mounting integrity to the upper coupler, and cracks.
105
Where are the upper coupler assemblies built?
Into the trailer assembly. \_The bolster plate is the lower plate in the assembly and provides the weight-bearing and pivot surface for the tractor fifth wheel plate when coupled. \_The upper coupler assembly should be inspected for mounting integrity, wear, cracks, plate distortion, and bowing.
106
What is the pintle hook and what does it do?
Is a device used to engage the drawbar of a towed vehicle. \_The locking mechanism may be mechanical, pneumatic, or hydraulic. \_Always make sure that the pintle hook is compatible with the drawbar eye on the tow vehicle. Most pintles are made to conform to Society of Automotive Engineers (SAE) Standard J133.
107
How would you inspect the pintle hooks and drawbars?
Perform a visual inspection on pintle hooks and drawbars to confirm structural integrity of the components (check for cracks, welds, deformation, etc.). \_Install pintle hooks and drawbars of the appropriate grade of material to achieve or exceed rated loads. \_Repair only if manufacturer's specifications can be achieved by repair method. Replace if necessary.
