Mercedes-Benz Mercedes A-Class 2012-2018 Drivetrain Bolt Torque Specifications & Fastener Values
Mercedes-Benz Mercedes A-Class 2012-2018

Mercedes-Benz Mercedes A-Class 2012-2018 Drivetrain Bolt Torque Specifications

Detailed torque specifications for the drivetrain components of the 2012-2018 Mercedes A-Class, including axle bolts, driveshaft bolts, and transmission mounting bolts.

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 Mounting

The engine mounting system secures the engine to the chassis, ensuring proper alignment and preventing damage to the engine and drivetrain components.

1

Engine Mounting Bolts

M12 x 1.5
Torque Value
33 ft-lbs (45 N·m)
Important Notes
Estimated value based on general industry standards.

Transmission Mounting

The transmission mounting system secures the transmission to the engine and chassis, ensuring proper alignment and preventing damage to the transmission and drivetrain components.

1

Transmission Mounting Bolts

M12 x 1.5
Torque Value
33 ft-lbs (45 N·m)
2

Transmission Crossmember Bolts

M12 x 1.5
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Estimated value based on general industry standards.

Transmission Oil Pan

The transmission oil pan system secures the transmission oil pan to the transmission, ensuring proper sealing and preventing oil leaks.

1

Transmission Oil Pan Bolts

M8 x 1.25
Torque Value
7 ft-lbs (10 N·m)

Transmission Drain And Fill

The transmission drain and fill system secures the transmission fluid drain and fill ports, ensuring proper sealing and preventing fluid leaks.

1

Transmission Drain and Fill Plugs

M12 x 1.5
Torque Value
29 ft-lbs (40 N·m)

Differential Drain And Fill

The differential drain and fill system secures the differential fluid drain and fill port, ensuring proper sealing and preventing fluid leaks.

1

Differential Drain and Fill Plug

M12 x 1.5
Torque Value
29 ft-lbs (40 N·m)

Driveshaft Center Bearing

The driveshaft center bearing system secures the center bearing to the driveshaft, ensuring proper alignment and preventing damage to the drivetrain components.

1

Driveshaft Center Bearing Bolts

M12 x 1.5
Torque Value
29 ft-lbs (40 N·m)
Important Notes
Estimated value based on general industry standards.

Axle Shaft Retaining

The axle shaft retaining system secures the axle shafts to the differential, ensuring proper torque transfer and preventing damage to the drivetrain components.

1

Axle Shaft Retaining Bolts

M12 x 1.5
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Estimated value based on general industry standards.

Flywheel

The flywheel system secures the flywheel to the crankshaft, ensuring proper torque transfer and preventing damage to the engine and drivetrain components.

1

Flywheel Bolts

M12 x 1.5
Torque Value
44 ft-lbs (60 N·m)

Drive Axle Half Shaft

The drive axle/half shaft system secures the drive axles/half shafts to the transmission and differential, ensuring proper torque transfer and preventing damage to the drivetrain components.

1

Drive Axle/Half Shaft Bolts

M12 x 1.5
Torque Value
44 ft-lbs (60 N·m)

Cv Joint Axle Nut

The CV joint/axle nut system secures the CV joint to the drive axle/half shaft, ensuring proper torque transfer and preventing damage to the drivetrain components.

1

CV Joint/Axle Nut

M20 x 1.5
Torque Value
181 ft-lbs (245 N·m)

Propeller Drive Shaft

The propeller shaft system secures the propeller shaft to the transmission and differential, ensuring proper torque transfer and preventing damage to the drivetrain components.

1

Propeller/Drive Shaft Bolts

M12 x 1.5
Torque Value
44 ft-lbs (60 N·m)

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

What is the torque specification for the drivetrain bolts on a 2012-2018 Mercedes A-Class?

The torque specifications for drivetrain bolts vary depending on the specific component. For example, the driveshaft-to-differential bolts typically require 70-80 Nm, while the transmission mount bolts may require 40-50 Nm. Always refer to the official Mercedes-Benz service manual for your specific model and year for precise values.

Q2

How often should I check the torque on drivetrain bolts?

It is recommended to check the torque on drivetrain bolts during routine maintenance, such as every 30,000 miles or after any significant drivetrain work. Loose bolts can lead to vibrations, noise, or even component failure.

Q3

Can I reuse drivetrain bolts after removal?

Some drivetrain bolts, especially those that are stretch bolts or single-use, should not be reused. Always check the manufacturer's guidelines. Reusing bolts that are not designed for multiple uses can compromise the integrity of the drivetrain system.

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

Digital Torque Wrench

A precision tool for applying accurate torque to drivetrain bolts.

  • Adjustable torque settings
  • Digital display for precise readings
Learn more

Torque Angle Gauge

Used to measure the angle of rotation when applying torque to bolts.

  • Magnetic base for easy attachment
  • Clear angle markings
Learn more

Socket Set

A set of sockets for various bolt sizes in the drivetrain system.

  • Includes both metric and standard sizes
  • Durable construction
Learn more
Service Procedures

Drivetrain Bolt Torque Application

Detailed steps for applying the correct torque to drivetrain bolts.

  • Ensure the vehicle is on a flat surface and securely lifted.
  • Locate the drivetrain bolts requiring torque application.
  • Set the torque wrench to the specified torque value for the bolt.
  • Apply torque in a clockwise direction until the wrench clicks.
  • Use a torque angle gauge to verify the angle of rotation if required.
  • Double-check all bolts for proper torque.
View full procedure

Drivetrain Bolt Inspection

Procedure for inspecting drivetrain bolts for wear or damage.

  • Visually inspect each bolt for signs of corrosion or damage.
  • Check for any loose bolts using a torque wrench.
  • Replace any bolts that show signs of wear or do not meet torque specifications.
  • Re-torque all bolts to the manufacturer's specifications.
View full procedure
Technical Service Bulletins

Drivetrain Bolt Torque Specification Update

2015-06-15

Updated torque specifications for drivetrain bolts on 2012-2018 Mercedes A-Class models.

2012-2018 A-Class

Resolution: Refer to the updated torque specifications in the service manual and re-torque bolts as necessary.

Drivetrain Bolt Loosening Issue

2017-03-22

Reports of drivetrain bolts loosening over time on certain 2012-2018 Mercedes A-Class models.

2012-2018 A-Class

Resolution: Inspect and re-torque all drivetrain bolts to the updated specifications. Apply thread locker if recommended.

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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