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Gmc M340 Alternator Bushings

Gmc M340 Alternator bushings

Alternator bushings start at low prices at AutoBuffy, where you'll find multiple options from top OE-quality brands. The alternator bushing is a small rubber or polyurethane isolator that cushions the alternator mount, absorbing vibration and preventing metal-to-metal contact. When it wears out, the alternator shifts out of alignment, accelerating belt wear and risking charging system failure.

Signs your Gmc M340 needs a new alternator bushing

  • A persistent rattling or clunking noise from the alternator mount area that worsens with engine RPM
  • Visible cracking, crumbling, or complete collapse of the rubber bushing material on inspection
  • Alternator sitting visibly cocked or misaligned in its bracket rather than sitting square
  • Accelerated or uneven serpentine belt wear caused by the alternator pulley running out of plane
  • Intermittent charging warning light triggered by micro-movements shifting the alternator's position
  • Excessive alternator bracket or mounting bolt wear from metal contact where the bushing has disintegrated

Which alternator bushing should you buy for your Gmc M340?

Alternator bushings differ mainly in material and whether they are sold as individual isolators or as part of a mounting kit. The right choice depends on how much vibration your engine produces, your budget, and whether original mounting hardware also needs replacement. Matching the bushing's inner diameter and outer diameter to your alternator bracket is essential before ordering.

OE-Spec Rubber Bushing
Best for
Daily drivers wanting a like-for-like factory replacement
What you get
Matched hardness and dimensions to original spec; quiet, compliant ride for the alternator mount
Polyurethane Bushing
Best for
High-mileage vehicles or those with heavy accessory loads wanting longer service life
What you get
Firmer material that resists oil and heat better than rubber; may transmit slightly more vibration
Bushing & Sleeve Kit
Best for
Vehicles where the metal sleeve or collar inside the bushing is also worn or corroded
What you get
Complete insert with inner metal sleeve and outer rubber or poly layer; restores full mount integrity in one step
Full Alternator Mount Hardware Kit
Best for
High-mileage rebuilds or cases where brackets, bolts, and bushings are all degraded
What you get
Bushing plus mounting bolts, washers, and sleeves; eliminates the need to source individual fasteners separately

Replacing the alternator bushing on a Gmc M340

Easy⏱ 30–60 minutesSocket set and ratchetCombination wrenchesPry bar or breaker bar for belt tension releaseRubber mallet or small punch for bushing removal and installationFlashlight or work light

Relieve tension on the serpentine belt and move it off the alternator pulley, then remove the alternator mounting bolts to free the unit enough to access the bushing. Drive or press the old bushing out, seat the new one fully and evenly in the bracket, then reinstall the alternator and re-tension the belt according to your vehicle's service procedure. Before closing the hood, run the engine briefly and inspect the mount and belt alignment to confirm everything sits correctly.

Frequently asked questions

How much does it cost to replace alternator bushings on a Gmc M340?
Parts start at low prices for the bushing itself. Because the job is typically straightforward — loosening the alternator, swapping the bushing, and realigning the belt — labor at a shop usually adds one hour or less. Total out-of-pocket cost stays modest compared to most charging-system repairs, especially if you do it yourself.
Can a worn alternator bushing damage the alternator on a Gmc M340?
Yes. A failed bushing allows the alternator to shift under load, misaligning the pulley with the serpentine belt. That misalignment increases side-load stress on the alternator's front bearing, shortening its life significantly. Replacing the bushing promptly protects both the belt and the alternator bearings from premature failure.
How long do alternator bushings last on a Gmc M340?
Rubber alternator bushings typically last many years under normal conditions, but heat cycles, oil contamination, and high-vibration engine environments can degrade them much faster. Inspect the bushing whenever you replace the serpentine belt. Polyurethane bushings generally outlast rubber in harsh conditions.
Is replacing an alternator bushing on a Gmc M340 a DIY job?
For most vehicles it is a straightforward task requiring basic hand tools. You loosen the alternator, slide out the old bushing, press or tap in the new one, and re-tension the belt. No special pullers are usually needed. The main challenge is accessing the alternator mount on engines with tight underhood packaging.
Will a bad alternator bushing cause a belt squeal on a Gmc M340?
It can. When the bushing collapses, the alternator pulley moves out of alignment with the other drive pulleys, causing the serpentine belt to run at a slight angle. That misalignment generates friction and heat, which often produces squealing or chirping, especially at startup or during accessory load increases like turning on the AC.
How do I know if I need just the bushing or the entire alternator mount bracket on my Gmc M340?
Inspect the metal bracket itself for cracks, elongated bolt holes, or stripped threads. If the bracket is structurally sound and damage is limited to the rubber or poly isolator, the bushing alone is sufficient. Elongated holes or cracked metal mean the bracket needs replacement too, which a bushing kit alone will not fix.

More parts for your Gmc M340

Vehicle BatteryAuxiliary Engine Cooling Fan RelayIgnition CondenserStarter DriveHorn RelayShock Absorber SetDistributor Primary Lead WireStarter Solenoid

Alternator bushings for other Gmc models

Gmc 100-24Gmc 150-22Gmc FM340Gmc P150-22Gmc PM152Gmc 350-27