BMW 640i 2018-present Drivetrain Bolt Torque Specifications & Fastener Values
BMW 640i 2018-present

BMW 640i 2018-present Drivetrain Bolt Torque Specifications

Comprehensive guide to the drivetrain bolt torque specifications for the 2018-Present BMW 640i (G32 generation). Includes torque values for transmission, driveshaft, and differential components.

Updated

Important Information

Safety guidelines and reference information for proper torque application

Quick Reference Guide
ft-lbs → Nm
× 1.356
ft-lbs → kg-m
× 0.138
Nm → ft-lbs
× 0.738
in-lbs → ft-lbs
× 0.083

Common Torque Patterns

Star Pattern

Used for wheels and other circular bolt patterns

Star Pattern torque pattern diagram showing proper bolt tightening sequence
Cross Pattern

Used for gaskets and cover plates

Cross Pattern torque pattern diagram showing proper bolt tightening sequence
Sequential Pattern

Used for head bolts and other critical components

Sequential Pattern torque pattern diagram showing proper bolt tightening sequence

Common Mistakes to Avoid

Over-tightening

Exceeding the specified torque value can stretch or break fasteners, damage threads, or crack components.

Prevention:

Always use a calibrated torque wrench and follow specifications exactly.

Incorrect Torque Sequence

Tightening bolts in the wrong order can cause uneven pressure distribution and potential leaks or damage.

Prevention:

Follow the manufacturer's specified torque sequence pattern.

Dirty Threads

Dirt, rust, or old thread locker can affect torque readings and proper fastener tension.

Prevention:

Clean and inspect all threads before assembly. Use new thread locker if specified.

Reusing TTY Bolts

Torque-to-yield bolts are designed to stretch and must not be reused.

Prevention:

Always replace TTY bolts with new ones. They are single-use only.

Dry vs. Lubricated

Not accounting for whether torque specs are for dry or lubricated fasteners can lead to incorrect tension.

Prevention:

Check if specs are for dry or lubricated threads. Use specified lubricant when required.

Recommended Tools

Torque Wrench (1/4" Drive)

Range: 2-25 ft-lbs
Small fasteners, delicate components

Torque Wrench (3/8" Drive)

Range: 10-100 ft-lbs
Most common automotive fasteners

Torque Wrench (1/2" Drive)

Range: 30-250 ft-lbs
Large fasteners, wheels

Angle Gauge

Torque-to-yield (TTY) bolts

Torque Wrench Care

  • Calibrate annually or after 5,000 clicks
  • Store at lowest setting
  • Keep clean and lubricated

Search Specifications

Search by component name, bolt size, or description

Torque Calculator

Convert between different torque units

Engine To Transmission

This section covers the components connecting the engine and transmission, crucial for transferring engine power to the drivetrain.

1

Flywheel Bolts

M10 x 1.25
Important Notes
Tighten bolts in a star pattern in two stages to ensure even clamping force. Final torque is crucial for preventing flywheel slippage and vibrations.
2

Transmission Mounting Bolts

M12 x 1.75
Torque Value
40 ft-lbs (54 N·m)
Important Notes
Ensure the transmission is properly aligned before tightening the mounting bolts. Proper torque is critical for transmission alignment and preventing vibrations.

Transmission

This section includes torque specifications for the transmission case, fluid access points and internal components.

1

Transmission Oil Pan Bolts

M6 x 1.0
Torque Value
10 ft-lbs (14 N·m)
Important Notes
Tighten in a criss-cross pattern to ensure even sealing. Overtightening can damage the pan or gasket.
2

Transmission Drain and Fill Plugs

M18 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Use a new sealing washer or o-ring on each plug. Do not overtighten to prevent damage to the transmission case.
3

Output Shaft Flange Bolts

M10 x 1.25
Torque Value
50 ft-lbs (68 N·m)
Important Notes
These bolts connect the output shaft flange to the transmission. Proper torque is critical for reliable power transfer. Estimated value.

Driveshaft

This section details the torque specs for components connecting the transmission and differential, vital for transmitting rotational power.

1

Flex Disc Bolts (Guibo)

M12 x 1.5
Important Notes
Tighten in a star pattern in two stages to ensure even clamping force and proper alignment. Estimated value. Use new bolts.
2

Propeller/Drive Shaft Bolts

M10 x 1.25
Torque Value
45 ft-lbs (61 N·m)
Important Notes
Ensure the driveshaft is properly centered before tightening. Proper torque is essential for preventing vibrations at high speeds.

Differential

This section covers torque specs for mounting the differential housing and accessing its fluid.

1

Differential Mounting Bolts

M14 x 2.0
Torque Value
70 ft-lbs (95 N·m)
Important Notes
These bolts secure the differential housing to the chassis or subframe. Ensure proper alignment before tightening. Estimated Value
2

Differential Drain/Fill Plug

M18 x 1.5
Torque Value
30 ft-lbs (40 N·m)
Important Notes
Use a new sealing washer or o-ring on the plug. Do not overtighten to prevent damage to the differential case.

Axles

This section covers the torque specifications for the drive axles, half shafts and their associated CV joints.

1

Drive Axle/Half Shaft Bolts

M10 x 1.5
Important Notes
Tighten bolts evenly in a circular pattern. These bolts secure the axle to the transmission or differential and wheel hubs.
2

CV Joint/Axle Nut

M24 x 1.5
Torque Value
185 ft-lbs (251 N·m)
Important Notes
Use a new nut and ensure it's properly seated before tightening. Proper torque is crucial for wheel bearing preload and axle retention.

Transfer Case

This section covers the torque specifications for the transfer case, used in 4WD and AWD vehicles

1

Transfer Case Drain/Fill Plug

M18 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Use a new sealing washer or o-ring on the plug. Do not overtighten to prevent damage to the transfer case.

Troubleshooting Guide

Common issues, diagnostic steps, and prevention guidelines

Common Issues

Bolt stretching, stripped threads, uneven torque patterns

Loose Components

Symptoms:
  • Rattling or vibration noises
  • Visible movement in components
  • Uneven panel gaps
Solutions:
  • Clean threads and mounting surfaces
  • Replace damaged fasteners
  • Apply proper torque in sequence
  • Use thread locker if specified

Stripped Fasteners

Symptoms:
  • Unable to achieve proper torque
  • Fastener spins freely
  • Visible thread damage
Solutions:
  • Use thread repair kit if appropriate
  • Install thread insert (HeliCoil)
  • Replace component if threaded hole is damaged
  • Upgrade to higher grade fastener if recommended

Overtightened Components

Symptoms:
  • Cracked or deformed parts
  • Broken fasteners
  • Compressed gaskets or seals
Solutions:
  • Replace damaged components
  • Use new fasteners
  • Follow proper torque sequence
  • Verify correct torque specifications

Diagnostic Steps

Visual inspection, torque verification, thread assessment

1

Visual Inspection

Inspect the affected area for any visible signs of damage or wear

  • Check for cracks or deformation
  • Look for signs of excessive wear
  • Verify proper fastener installation
2

Torque Verification

Verify the torque applied to the fasteners

  • Check the torque wrench calibration
  • Verify the torque specification
  • Compare the applied torque to the specification
3

Thread Assessment

Assess the condition of the threads

  • Check for signs of thread damage
  • Verify the thread type and size
  • Check for proper thread engagement

Prevention Guidelines

Best practices, maintenance tips, tool care

Best Practices

  • Always follow the recommended torque specification
  • Use the correct type and size of fasteners
  • Verify the torque wrench calibration regularly

Maintenance Tips

  • Regularly inspect the affected area for signs of wear or damage
  • Replace damaged or worn-out components promptly
  • Keep the work area clean and organized

Tool Care

  • Regularly clean and maintain the torque wrench
  • Store the torque wrench in a dry and secure location
  • Verify the torque wrench calibration before each use

Frequently Asked Questions

Find answers to common questions about torque specifications

Q1

Why is using the correct torque specification important for drivetrain bolts?

Using the correct torque ensures proper clamping force. Under-torquing can lead to bolts loosening, causing vibrations, damage, or even component failure. Over-torquing can stretch or break bolts, strip threads, or damage mating surfaces, potentially causing catastrophic failure of drivetrain components. For example, an improperly torqued driveshaft bolt could detach at high speed, resulting in loss of vehicle control.

Q2

Should I use new bolts when reassembling the drivetrain?

It's generally recommended to use new bolts, especially for critical components like the driveshaft, transmission mounting, and differential. Many drivetrain bolts are designed for one-time use (torque-to-yield), and reusing them can compromise their structural integrity, leading to failure. BMW often specifies using new bolts in repair procedures. For example, reusing a driveshaft bolt that has been previously torqued could result in it failing at lower-than-expected loading.

Q3

What type of lubricant should be used on drivetrain bolts?

Unless otherwise specified by BMW, use a thread locker compound or lubricant as specified in the service manual. Applying the incorrect lubricant can alter the friction coefficient, resulting in inaccurate torque application. For example, using an anti-seize compound on a bolt specified to be torqued dry will dramatically increase the clamping force and can potentially overstress the bolt.

Q4

What if I don't have a torque wrench?

It is highly discouraged to attempt drivetrain bolt tightening without a calibrated torque wrench. Guessing or relying on 'feel' is highly unreliable and can lead to severe consequences. Consider borrowing or renting a torque wrench. Improper tightening can lead to major problems in the drivetrain. For example, an improperly torqued wheel bolt can loosen and cause the wheel to come off.

Q5

How often should I check the torque of drivetrain bolts?

While specific maintenance intervals vary, it’s a good practice to check drivetrain bolt torques during major services, after significant impacts, or if unusual noises or vibrations are noticed. For daily driven vehicle, a yearly check during seasonal tire swap or routine service would be a beneficial preventative action, especially for older vehicles or vehicles that have been modified. This simple check can prevent failures in the long term.

Environmental Considerations

Temperature, humidity, and seasonal effects on torque specifications

Temperature Effects

Includes: High Heat, Cold Weather, Thermal Cycling

Temperature can significantly impact torque values and fastener behavior

Cold Weather

Effects:
  • Increased material brittleness
  • Higher torque required due to thread contraction
  • Reduced thread lubricant effectiveness
Recommendations:
  • Allow components to warm to room temperature when possible
  • Consider using winter-grade thread lubricants
  • Check torque values more frequently during winter months

Hot Weather

Effects:
  • Thermal expansion of components
  • Decreased friction in threads
  • Accelerated lubricant breakdown
Recommendations:
  • Check torque when components are at normal operating temperature
  • Use temperature-resistant thread lockers
  • Consider re-torquing after heat cycles

Humidity and Corrosion

Covers: Rust Prevention, Salt Exposure, Moisture Control

Moisture and corrosion can affect fastener integrity and torque values

High Humidity

Effects:
  • Accelerated corrosion formation
  • Reduced friction coefficient
  • Potential thread seizing
Prevention:
  • Use corrosion-resistant fasteners
  • Apply appropriate anti-seize compounds
  • Maintain proper protective coatings

Salt Exposure

Effects:
  • Rapid corrosion development
  • Thread damage
  • Seized fasteners
Prevention:
  • Regular underbody washing
  • Use of sacrificial anodes where appropriate
  • Application of protective coatings

Seasonal Maintenance

Spring, Summer, Fall, and Winter maintenance schedules

Spring

  • Inspect for winter damage
  • Clean and protect exposed fasteners
  • Check torque on critical components

Summer

  • Monitor heat-affected components
  • Check expansion-related loosening
  • Inspect cooling system mounts

Fall

  • Prepare for winter conditions
  • Apply corrosion protection
  • Verify all fasteners are properly torqued

Winter

  • More frequent inspection of critical fasteners
  • Check for salt damage
  • Monitor suspension component torque

Related Resources

Tools, service procedures, and technical bulletins

Recommended Tools

Torque Wrench (1/2" Drive)

A calibrated torque wrench is essential for achieving accurate bolt torque specifications.

  • Wide torque range (e.g., 20-200 Nm)
  • Audible click when target torque is reached
Learn more

Torque Wrench (3/8" Drive)

A smaller torque wrench for lower torque applications, typically in the transmission area.

  • Lower torque range (e.g., 5-80 Nm)
  • Compact for tighter spaces
Learn more

Socket Set (Metric)

A comprehensive set of metric sockets of various sizes to match the bolt head sizes used in the drivetrain.

  • Variety of sizes (e.g., 8mm-24mm)
  • Impact-rated sockets recommended
Learn more

Wobble Extensions

Allows access to hard-to-reach bolts or those at odd angles.

  • Various lengths available
  • Flexible movement
Learn more
Service Procedures

Driveshaft Bolt Torque Procedure

Procedure for correctly torquing the bolts connecting the driveshaft to the transmission and differential.

  • 1. Identify all driveshaft bolts to be torqued.
  • 2. Verify the correct torque specification in the vehicle's service manual.
  • 3. Clean threads of the bolts and corresponding holes on both sides.
  • 4. Apply new, factory-recommended bolts.
  • 5. Install the bolts by hand and ensure they are seated straight.
  • 6. Tighten all bolts in a star or criss-cross pattern in stages.
  • 7. Use the correct torque wrench and apply the proper torque specification to each bolt in the sequence.
  • 8. Recheck the torque on each bolt again to ensure no movement has occurred and each bolt is properly torqued.
View full procedure

Differential Mounting Bolt Torque Procedure

Procedure for correctly torquing the bolts mounting the differential to the chassis.

  • 1. Identify all differential mounting bolts.
  • 2. Verify correct torque specification in the service manual.
  • 3. Clean threads of bolts and corresponding holes.
  • 4. Install new, factory-recommended bolts.
  • 5. Install the bolts by hand and ensure they are seated straight.
  • 6. Tighten all bolts evenly in stages.
  • 7. Use the correct torque wrench and torque to the final specification.
  • 8. Recheck the torque on each bolt to ensure no movement and correct torque.
View full procedure

Transmission Mounting Bolt Torque Procedure

Procedure for correctly torquing the bolts mounting the transmission to the engine and chassis.

  • 1. Identify all transmission mounting bolts.
  • 2. Verify the correct torque specification in the service manual.
  • 3. Clean threads of bolts and corresponding holes.
  • 4. Install new, factory-recommended bolts.
  • 5. Install bolts by hand and ensure they are seated straight.
  • 6. Tighten all bolts evenly in stages
  • 7. Use the correct torque wrench and torque each bolt to the final specification in the correct sequence.
  • 8. Recheck the torque of each bolt to ensure no movement and correct torque.
View full procedure
Technical Service Bulletins

Incorrect Driveshaft Bolt Torque

2020-05-15

Some vehicles may have been assembled with incorrect driveshaft bolt torque specifications. This can cause premature bolt failure and vibration.

2018-2020 BMW 640i

Resolution: Verify driveshaft bolt torque using a calibrated torque wrench and correct specification. Replace all affected bolts if necessary.

Differential Mounting Bolt Fatigue

2022-11-20

A potential issue has been found with the differential mounting bolts, where they may fatigue after extended use. This can cause noise and unwanted drivetrain movement.

2018-2022 BMW 640i

Resolution: Inspect differential mounting bolts and replace with new, updated bolts using the correct torque specification.

Transmission Mounting Bolt Breakage

2023-01-20

Reports of transmission mounting bolt breakage under higher load, especially in vehicles with high mileage.

2018-Present BMW 640i

Resolution: Inspect transmission mounting bolts, if any signs of wear are present replace with new updated bolts. Use a calibrated torque wrench and torque to specification.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

ASE Master Certified Technician with over a decade of hands-on experience in automotive repair and diagnostics.

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