The flexplate connects the engine to the torque converter. It's a thin metal disc that flexes slightly under load. When it cracks or fails, you'll know it. Here's the complete guide to flexplates.
Shop rebuild kits and parts by transmission
What the flexplate does
The flexplate:
- Connects crankshaft to torque converter
- Provides ring gear for starter
- Flexes slightly during operation (absorbs vibration)
- Mounts to the engine flange and converter
When the flexplate fails:
- Cracking sound from bellhousing area
- Vibration during acceleration
- Starter grinding (worn teeth)
- Engine misfires from improper rotation
- Eventually: complete failure, won't start
When to replace
Mandatory replacement:
- During engine swap
- During trans swap
- During converter replacement (sometimes)
- When cracked
- When ring gear teeth worn
Recommended replacement:
- Engine over 200K miles
- HD applications (towing, performance)
- After any significant impact (collision, ground strike)
- Race / drag applications (preventive)
Inspection during other work:
- During trans rebuild
- During converter replacement
- During engine work (front or rear seal, oil pan)
Common failures
1. Cracked flexplate
Cause: Vibration, age, heavy use, misalignment
Symptoms: Knocking/ticking sound from bellhousing, vibration
Severity: Must fix before catastrophic failure
2. Worn ring gear teeth
Cause: Starter engagement over time
Symptoms: Starter grinding, intermittent starts, partial engagement
Severity: Replace before starter damage
3. Loose flexplate
Cause: Bolts loosening, improper torque at install
Symptoms: Vibration, sometimes "clunk" on acceleration
Severity: Address immediately
4. Damaged bolt holes
Cause: Misalignment during install, excessive torque
Symptoms: Bolts loosen repeatedly, vibration
Severity: Replace flexplate
5. Bent flexplate (rare)
Cause: Impact (driveshaft hit), severe vibration
Symptoms: Severe vibration, possible starter issues
Severity: Replace immediately
Flexplate types by application
Stock automotive grade
Material: Stamped steel
Pros: Cheap, OE quality
Cons: Can crack under HD use
Cost: $40-100
HD aftermarket
Material: Higher-grade steel
Pros: Better fatigue resistance
Cons: Slightly more expensive
Cost: $60-150
SFI-certified racing flexplate
Material: Race-grade steel, additional reinforcement
Pros: Required for many race classes, ultimate strength
Cons: Expensive
Cost: $150-400
Billet flexplate
Material: CNC-machined from billet steel
Pros: Maximum strength, precision balance
Cons: Most expensive
Cost: $300-800
Specific applications
4L60E behind small block Chevy
- Standard 168-tooth flexplate
- Stock: $50-80
- HD aftermarket: $80-150
- SFI-rated race: $150-300
4L60E behind LS engine
- Specific LS flexplate (different from SBC)
- 168-tooth typical
- Stock: $60-100
- HD: $100-180
- Race: $200-400
4L80E behind big block
- HD flexplate required for HD applications
- Stock: $80-150
- HD: $150-300
- Race: $300-500
6L80 / 8L90 behind LS / LT
- Stock OEM: $80-150
- Aftermarket: $100-200
700R4 behind small block
- Standard 168-tooth
- Stock: $40-80
- HD: $80-150
TH400 behind big block
- Standard pattern
- Stock: $50-100
- HD: $100-200
- Race: $200-500
TH400 behind small block
- Standard pattern, often interchanges
- Stock: $50-100
47RE / 48RE behind 5.9L Cummins
- Specific HD flexplate
- Stock: $80-150
- HD: $150-300
68RFE behind 6.7L Cummins
- HD flexplate from factory
- Replacement: $100-250
- HD upgrade: $200-400
Allison behind Duramax
- Heavy-duty flexplate from factory
- Replacement: $150-300
Ford 4R70W behind small block Ford
- Ford pattern (different from GM)
- Stock: $50-100
- HD: $100-200
Ford 6R80 / 10R80 behind modular V8
- OEM Ford: $80-200
- Aftermarket: $100-250
Tooth count
168 teeth (most common)
- Small block Chevy
- LS series
- 4L60E, 700R4, TH350, TH400 (small block applications)
- Most common configuration
153 teeth (less common)
- Some small block Chevy applications
- Smaller starter pinion
- Verify your starter
Specific Ford counts
- Various tooth counts depending on engine
- Verify before purchasing
Diesel applications
- Different tooth counts
- Verify with engine spec
Always verify tooth count for your specific engine and starter combination.
Installation tips
Torque spec
Flexplate-to-crank bolts: typically 60-75 ft-lb (verify service manual)
Converter-to-flexplate bolts: typically 35-45 ft-lb (verify service manual)
Use new bolts
Always use new flexplate bolts (manufacturer recommended). They're stretched on initial torque.
Verify balance
- 153T and 168T may have different balance characteristics
- Match factory balance (internal vs external balance)
- Wrong balance = vibration
Internal vs external balance:
- Small block Chevy: Internal balance (no counterweight on flexplate needed)
- Big block Chevy: Internal balance
- LS engines: Internal balance
- Some Ford engines: External balance (counterweight on flexplate required)
Wrong balance = severe vibration. Verify with engine manual.
Torque converter bolt sequence
Hand-tighten all bolts first. Then torque in cross sequence. Verify converter is fully seated before torquing.
Brand recommendations
Standard OEM-quality
- ACDelco
- Motorcraft
- Mopar (for Cummins)
- GM / OEM equivalent
HD aftermarket
- ATP
- Pioneer
- Dura-Bond
Race / SFI-rated
- ATI
- TCI
- Hays
- BTE Performance
Billet race
- ATI billet
- TCI billet
- Inglewood Transmission
Cost summary
DIY replacement:
- Flexplate: $40-400 depending on grade
- New bolts: $15-30
- Gasket (if changed during related work): $10-40
- Total: $65-470
Shop replacement:
- Parts: $50-400
- Labor (trans must come out): $400-800
- Total: $450-1,200
Usually flexplate is replaced as part of other work (trans rebuild, converter replacement), keeping labor cost down.
Common installation mistakes
Mistake 1: Wrong tooth count
Doesn't match starter. Won't engage properly.
Mistake 2: Wrong balance
Internal vs external mismatch = vibration.
Mistake 3: Bolt sequence
Wrong sequence = warped flexplate.
Mistake 4: Wrong torque
Under-torque: loosens. Over-torque: damaged bolts/flexplate.
Mistake 5: Reusing bolts
Stretched bolts don't have same clamping force.
Mistake 6: Not verifying converter seating
Converter must fully engage with input shaft before flexplate bolts go in. Otherwise pump damage.
Mistake 7: Cheap eBay flexplate
Inferior steel, poor balance, short life.
When to upgrade to HD or race flexplate
Stay with stock if:
- Daily driver
- Stock power
- No race / track use
Upgrade to HD if:
- Tow rig
- Performance daily driver
- Higher torque application
Upgrade to race if:
- Drag race
- Sled pull
- Race-class requirement (SFI certification)
- 600+ HP applications
What we sell
OEM-quality flexplates from ACDelco, Motorcraft, Mopar, and quality aftermarket brands. HD aftermarket options for tow and performance. SFI-certified race flexplates from ATI, TCI, and Hays. Plus new flexplate bolts.
Need a flexplate? Shop our flexplate catalog. Stock, HD, and race flexplates for every common engine and transmission combination. Free shipping over $70.
Related guides: