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Kenworth K100 Leaf Spring Bolts

Kenworth K100 Leaf spring bolts

Leaf spring bolts for your Kenworth K100 start at $72.95, and AutoBuffy stocks 1 options from MOOG. These fasteners clamp the leaf spring pack together and secure it to the axle U-bolt plates and shackle mounts. When they corrode, stretch, or shear, the spring assembly shifts under load, causing dangerous handling changes and accelerating wear on surrounding suspension components.

Signs your Kenworth K100 needs new leaf spring bolts

  • Clunking or banging from the rear suspension over bumps, especially under load or when accelerating from a stop
  • Visible rust, corrosion, or a sheared bolt head when inspecting under the vehicle
  • Leaf spring pack has shifted laterally or fore-aft relative to the axle centerline
  • Uneven tire wear on the rear axle caused by the axle walking out of its correct position
  • Squeaking or creaking from the spring pack that gets louder as the vehicle is loaded
  • Loose or sloppy rear-end feel when cornering, braking, or towing, with no apparent shock absorber fault

Which leaf spring bolts should you buy for your Kenworth K100?

Leaf spring bolts are not one-size-fits-all — diameter, thread pitch, length, and grade all vary by application. Beyond fitment, the main decision is between OE-equivalent replacement hardware and upgraded high-strength or coated fasteners, which matters most if you tow, haul heavy loads, or live in a high-corrosion environment.

OE-Equivalent Grade 5 / Grade 8 Replacement
Best for
Daily drivers restoring stock suspension function
What you get
Correct factory diameter, thread pitch, and length; meets original torque spec; typically zinc plated for basic corrosion resistance
High-Strength Grade 10.9 / Grade 12.9 Metric or SAE Equivalent
Best for
Trucks and vans used for towing, hauling, or off-road use
What you get
Higher tensile and proof load ratings than OE; resists stretch and shear under repeated heavy-load cycles
Stainless Steel Leaf Spring Bolts
Best for
Vehicles in salt-belt regions or frequent off-road water crossings
What you get
Excellent corrosion resistance; lower tensile strength than alloy grades, so best on light-duty or mild-use applications
Complete U-Bolt and Center Pin / Bolt Kit
Best for
Any repair where the full spring pack is disassembled or U-bolts are also due for replacement
What you get
Includes center pin bolt, U-bolts, nuts, and washers as a matched set; eliminates mismatched hardware and simplifies the job

Leaf spring bolts brands we stock for your Kenworth K100

MOOG
1 option · from $72.95

Replacing leaf spring bolts on a Kenworth K100

Moderate⏱ 1–3 hoursFloor jack and jack stands rated for vehicle weightBreaker bar and socket set (metric and SAE)Torque wrenchPenetrating oil and wire brush for seized fastenersPickle fork or brass punch for driving out stubborn center pins

Support the vehicle frame securely on jack stands and allow the rear axle to hang free so spring tension is relieved before removing any fasteners. Soak corroded bolts with penetrating oil well in advance to reduce the risk of snapping a bolt in the mount. Torque all new fasteners to the manufacturer's specification for your Kenworth K100 with the suspension at normal ride height, not with the axle hanging, so rubber bushings are not preloaded in a twisted position.

Frequently asked questions

How much does it cost to replace leaf spring bolts on a Kenworth K100?
Parts alone start at $72.95 for a Kenworth K100 at AutoBuffy. A shop will typically add one to two hours of labor on top of that. Replacing all spring hardware at once — center bolts, U-bolts, and shackle bolts — costs more upfront but prevents a second disassembly shortly after.
Can I drive my Kenworth K100 with a broken or missing leaf spring bolt?
No. A broken center pin bolt allows the spring pack to shift on the axle pad, which changes rear axle alignment and can cause sudden loss of vehicle control. A missing shackle or mount bolt lets the entire spring move unpredictably under braking or cornering. Stop driving and repair it before returning the vehicle to the road.
How often should leaf spring bolts be replaced on a Kenworth K100?
There is no fixed mileage interval. Inspect them whenever the suspension is serviced or any spring component is removed. In rust-prone climates, surface corrosion can develop within a few years and seize the bolt, making future removal destructive. Replace any bolt that shows thread damage, elongation, or heavy pitting.
Do I need to replace all leaf spring bolts at once on a Kenworth K100?
Replacing the full set is strongly recommended. If one bolt has corroded or fatigued enough to fail, the others on the same axle have been exposed to identical conditions and stress cycles. Replacing only the failed fastener leaves the remaining hardware at similar risk and means the suspension will need to come apart again soon.
What happens if the center pin bolt breaks on a Kenworth K100?
The center pin bolt aligns the spring pack to the axle pad and prevents fore-aft movement. When it breaks, the axle can shift rearward or forward on one side, causing severe axle misalignment, sudden steer pull, and accelerated tire wear. It is a safety-critical fastener and must be replaced immediately when broken.
Are aftermarket leaf spring bolts safe for a Kenworth K100?
Yes, provided they match the correct grade, diameter, thread pitch, and length for your application. Verify that any aftermarket bolt meets or exceeds the OE strength specification. Avoid using generic hardware-store fasteners of unknown grade. Quality aftermarket kits from MOOG are engineered to correct vehicle specifications and are a reliable alternative to dealer parts.

Shop leaf spring bolts by year for the Kenworth K100

1984198319821981

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Leaf spring bolts for other Kenworth models

Kenworth K100EKenworth L700Kenworth W900Kenworth T800Kenworth T600AKenworth T450