GMT800 and GMT900 Fitment
The Silverado, Sierra, Tahoe, Yukon, Suburban and Avalanche ranges cross the transition from GMT800 to GMT900 vehicles.
For 2007, General Motors sold:
- Redesigned GMT900 trucks
- Previous-generation GMT800 trucks labeled “Classic”
The listing explicitly includes the 2007 Silverado 1500 Classic and Sierra 1500 Classic, along with certain new-body applications. Verify the VIN, engine and original starter number rather than assuming all 2007 trucks interchange.
Applications Not Confirmed
Do not automatically list the 6494N starter for:
- 4.2L inline-six GMT360 vehicles
- 6.0L V8 applications
- 6.2L V8 applications
- Duramax diesel engines
- 4.3L V6 engines
- 2500HD or 3500HD pickups
- Hybrid Tahoe, Yukon, Silverado or Sierra
- Trailblazer SS
- Saab 9-7X Aero
- Cadillac Escalade ESV or EXT
- Engine-swapped vehicles
- Vehicles with an unmatched original starter number
Replacement Part Numbers
This starter replaces or cross-references:
64946494N1256805112578050125922941260447789-01-744089-01-76318901744089017631800001680000458000150
Broader 6494 catalogs may also reference:
410-12257323-1483323-1623323-1644336-20028000288888619358901812312610300
Match the complete number on the original starter whenever possible.
1.1-kW PMGR Design
The starter is rated at 1.1 kW and uses a permanent-magnet gear-reduction design. PMGR starters use internal reduction gearing to produce cranking torque from a relatively compact electric motor.
Potential advantages include:
- Compact housing
- Reduced starter weight
- Efficient cranking
- Good exhaust clearance
- Lower current demand than some direct-drive designs
- Consistent operation on compatible engines
Actual performance still depends on battery health, cable condition and engine temperature.
Nine-Tooth Pinion
The starter uses a nine-tooth drive pinion. Correct tooth count alone does not establish fitment.
Compare:
- Pinion diameter
- Tooth pitch
- Resting position
- Starter nose length
- Mounting depth
- Flexplate configuration
- Solenoid position
An incompatible starter may cause:
- Grinding
- Free-spinning starter motor
- Partial engagement
- Broken pinion teeth
- Flexplate damage
- Delayed disengagement
- Starter kickback
Stop testing if grinding occurs after installation.
Fitment Verification
Before ordering, confirm:
- Model year
- Make and model
- 4.8L or 5.3L V8 engine
- Eighth VIN character
- GMT800, GMT900 or GMT360 platform
- Original starter number
- Mounting-flange design
- Bolt-hole spacing
- Pinion configuration
- Solenoid and terminal location
The NHTSA VIN decoder can help identify the vehicle and engine, but the original starter should still be inspected.
Diagnosing Starter Failure
Common starter symptoms include:
- One click without cranking
- Rapid clicking
- Intermittent no-crank
- Slow cranking
- Starter spinning without engagement
- Grinding
- Electrical burning odor
- Starting only after repeated attempts
Similar symptoms may result from:
- Weak battery
- Corroded battery terminals
- Damaged positive cable
- Poor engine ground
- Faulty starter relay
- Ignition-switch problem
- Park/Neutral switch fault
- Security-system problem
- Damaged flexplate teeth
- Internal engine damage
Test the starting circuit before replacing the starter. New parts are excellent, but they remain stubbornly unable to repair corroded battery cables through emotional support.
Battery and Voltage-Drop Testing
Before replacement, inspect:
- Battery open-circuit voltage
- Battery load-test result
- Positive-cable voltage drop
- Negative-cable voltage drop
- Starter-trigger voltage
- Engine-to-body ground
- Battery-terminal condition
- Starter relay
- Main fuses
Measure voltage drop while cranking. A cable can pass a continuity test while failing badly under starter load.
Installation Preparation
Before removing the original starter:
- Verify the 4.8L or 5.3L engine.
- Record the original starter number.
- Confirm the new starter specifications.
- Disconnect the negative battery terminal.
- Photograph the electrical connections.
- Compare the mounting flange and pinion.
- Inspect exhaust clearance.
- Obtain the correct torque specifications.
- Confirm whether mounting bolts are included.
The supplied package list identifies one starter but does not confirm included mounting hardware.
Installation Overview
A typical replacement includes:
- Disconnecting the negative battery cable.
- Raising and safely supporting the vehicle.
- Removing shields or braces restricting access.
- Labeling the starter wiring.
- Disconnecting the battery cable and trigger wire.
- Supporting the original starter.
- Removing its mounting bolts.
- Comparing the original and replacement units.
- Inspecting visible flexplate teeth.
- Installing the new starter.
- Torquing the mounting bolts correctly.
- Reconnecting the electrical terminals.
- Securing wiring away from exhaust components.
- Reinstalling shields and braces.
- Reconnecting the battery and testing operation.
Disconnect the battery first. The unfused starter cable carries enough current to make a dropped wrench extremely memorable.
One-Year Unlimited-Mileage Warranty
A-Premium advertises a one-year, unlimited-mileage warranty.
Before purchasing, confirm:
- Warranty start date
- Proof-of-purchase requirements
- Labor coverage
- Return-shipping responsibility
- Commercial-use exclusions
- Diagnostic requirements
- Consequential-damage coverage
Frequently Asked Questions
What vehicles does the A-Premium 6494N starter fit?
It fits select 2003–2009 GM-family trucks, SUVs and vans equipped with compatible 4.8L or 5.3L V8 engines.
Does it fit a Trailblazer with the 4.2L engine?
No. The advertised Trailblazer application is the 5.3L V8.
Does it fit an Envoy 4.2L?
No confirmed 4.2L compatibility is provided. Envoy fitment is for the 5.3L V8.
Does it fit a Trailblazer SS?
No. The Trailblazer SS uses a 6.0L engine and is not included.
Does it fit an Escalade 6.0L?
The listed Escalade application specifies 5.3L compatibility. Do not assume 6.0L fitment.
Does it fit a Silverado 2500HD?
No confirmed HD fitment is provided.
What are the starter specifications?
It operates at 12 volts, produces 1.1 kW and uses a nine-tooth pinion with clockwise rotation.
Which part number should I match?
The primary aftermarket numbers are 6494 and 6494N. Common GM numbers include 12568051, 12578050, 12592294 and 12604477.
What warranty is included?
A-Premium advertises one-year, unlimited-mileage coverage.
Final Verdict
The A-Premium 6494N starter provides a new PMGR replacement for a wide range of GM 4.8L and 5.3L V8 applications. Its 1.1-kW motor, nine-tooth pinion and extensive OE interchange make it suitable for many GMT800, GMT900 and V8-powered GMT360 vehicles.
Engine verification is the critical requirement. Exclude 4.2L GMT360 SUVs, 6.0L performance models, Duramax diesels, Hybrids and HD pickups unless a separate catalog explicitly confirms them.
Visit My Pro Street for additional GM starter diagnostics, electrical testing and replacement guides.
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