Audi Audi S8 2012-2018 AL551 Transmission Transmission Torque Specifications & Bolt Torque Values
Audi Audi S8 2012-2018

Audi Audi S8 2012-2018 AL551 Transmission Torque Specifications

Detailed torque specifications for all bolts related to the AL551 transmission used in the 2012-2018 Audi S8 (D4). Includes housing, pan, and valve body bolt torques.

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

Transmission Housing

Torque specifications for bolts related to the transmission housing, its mounting to the engine block, and to the chassis.

1

Transmission Housing to Engine Block Bolts

M12 x 1.75
Important Notes
Tighten bolts in a criss-cross pattern. Final step is an angle tightening. Estimated bolt size and thread pitch.
2

Transmission Mount Bolts (to Transmission Housing)

M12 x 1.75
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Estimated bolt size and thread pitch. Tighten all bolts to specification.
3

Transmission Mount Bolts (to Chassis)

M12 x 1.75
Important Notes
Tighten bolts in a criss-cross pattern. Final step is an angle tightening. Estimated bolt size and thread pitch.

Internal Components

Torque specifications for bolts securing internal components of the transmission, including the valve body, mechatronics unit, and oil pump.

1

Valve Body Mounting Bolts

M6 x 1.0
Torque Value
7.4 ft-lbs (10 N·m)
Important Notes
Tighten bolts in a criss-cross pattern. Converted from 89 in-lbs. Estimated bolt size and thread pitch.
2

Mechatronics Unit Bolts

M6 x 1.0
Torque Value
7.4 ft-lbs (10 N·m)
Important Notes
Tighten bolts in a criss-cross pattern. Converted from 89 in-lbs. Estimated bolt size and thread pitch.
3

Transmission Oil Pump Mounting Bolts

M6 x 1.0
Torque Value
7.4 ft-lbs (10 N·m)
Important Notes
Tighten bolts in a criss-cross pattern. Converted from 89 in-lbs. Estimated bolt size and thread pitch.
4

Park Lock Actuator Bolts

M6 x 1.0
Torque Value
7.4 ft-lbs (10 N·m)
Important Notes
Tighten bolts in a criss-cross pattern. Converted from 89 in-lbs. Estimated bolt size and thread pitch.

Fluid Management

Torque specifications for bolts related to the transmission fluid pan, drain plug, fill plug, and cooler lines.

1

Transmission Fluid Pan Bolts

M6 x 1.0
Torque Value
7.4 ft-lbs (10 N·m)
Important Notes
Tighten bolts in a criss-cross pattern. Converted from 89 in-lbs. Estimated bolt size and thread pitch.
2

Transmission Fluid Drain Plug

M18 x 1.5
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Always use a new crush washer. Estimated bolt size and thread pitch.
3

Transmission Fluid Fill Plug/Level Plug

M18 x 1.5
Torque Value
22 ft-lbs (30 N·m)
Important Notes
Always use a new crush washer. Estimated bolt size and thread pitch.
4

Transmission Cooler Line Fittings

M12 x 1.5
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Tighten fittings to specified torque. Estimated bolt size and thread pitch.

Power Transfer

Torque specifications for bolts related to the torque converter and output flange.

1

Torque Converter Bolts (to Flexplate/Drive Plate)

M10 x 1.5
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Tighten bolts evenly in a star pattern. Estimated bolt size and thread pitch.
2

Output Flange Bolt (Propeller Shaft Attachment)

M10 x 1.5
Important Notes
Always use new bolts. Final step is an angle tightening. Estimated bolt size and thread pitch.

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 are correct torque specifications important for the AL551 transmission?

Correct torque is crucial for proper clamping force, preventing leaks, and ensuring the structural integrity of the AL551 transmission. Over-tightening can damage threads or components, while under-tightening can lead to loosening and fluid leaks, ultimately causing transmission failure. For example, insufficient torque on the valve body bolts can cause shifting issues and internal leaks. A common symptom might be intermittent harsh shifting or a slipping sensation.

Q2

What happens if I over-torque a bolt on the AL551 transmission?

Over-torquing bolts can stretch or strip threads in the aluminum transmission case, permanently damaging it. It can also damage the bolt itself. This might mean the bolt won't hold properly after repairs and may lead to leaks or structural failure. Imagine over-tightening a pan bolt; you could crush the gasket or even crack the transmission case, requiring expensive repairs.

Q3

Should I use new bolts when working on the AL551 transmission?

It is generally recommended to use new bolts, particularly for critical components such as the valve body and mechatronic unit. Many bolts, especially those subjected to high loads or torque-to-yield applications, are designed for single use only. Reusing them can compromise clamping force and increase the risk of failure. For instance, reusing a torque-to-yield bolt on the transmission case can cause a leak due to insufficient clamping.

Q4

Are there any special tools required for torquing AL551 transmission bolts?

Yes, a calibrated torque wrench is essential to ensure accurate torque application. Depending on the specific location of bolts, you may need a variety of sockets, extensions, and even adapters to reach certain fasteners. For example, a torque angle meter may be required for specific bolts on the valve body. Using the wrong tools can lead to inaccurate readings and potential damage.

Q5

What should I do if a bolt feels like it is stripping while tightening?

If a bolt feels like it's stripping, stop immediately. Do not attempt to force it. If possible, try to gently remove the bolt to inspect for damage. You may need to helicoil the threads if they are stripped to ensure a proper torque value. Attempting to force a bolt that is stripping will damage the housing, requiring professional repair.

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 with a 1/2" drive is essential for applying accurate torque to transmission bolts.

  • Accurate torque measurement
  • Click-type mechanism for precise application
Learn more

Torque Wrench (3/8" Drive)

A 3/8" drive torque wrench may be needed for smaller, lower-torque bolts on the transmission.

  • Suitable for lower torque applications
  • Smaller size for tight spaces
Learn more

Socket Set (Metric)

A comprehensive metric socket set, including various sizes commonly found on the AL551 transmission.

  • Comprehensive range of socket sizes
  • Durable construction for repeated use
Learn more

Extension Bars and Universal Joints

Extension bars and universal joints may be necessary to access recessed or difficult-to-reach bolts.

  • Improved access to bolts
  • Allows torque application at angles
Learn more
Service Procedures

Mechatronic Unit Bolt Torque Procedure

This procedure outlines the correct steps for torquing the mechatronic unit bolts on the AL551 transmission.

  • Locate all mechatronic unit mounting bolts.
  • Using the correct size socket, loosely install all bolts by hand.
  • Refer to the vehicle repair manual for the specific torque values and tightening sequence.
  • Using the calibrated torque wrench, tighten the bolts in the correct sequence to the first stage torque specification.
  • Re-check all the bolts to ensure they have reached the first stage torque specification.
  • Continue to the final torque specification in the correct sequence as per the repair manual.
  • Re-check all the bolts to ensure they have reached the final torque specification.
View full procedure

Transmission Housing Bolt Torque Procedure

This procedure outlines the correct steps for torquing the main transmission housing bolts on the AL551 transmission.

  • Locate all transmission housing bolts.
  • Using the correct size socket, loosely install all bolts by hand.
  • Refer to the vehicle repair manual for the specific torque values and tightening sequence.
  • Using the calibrated torque wrench, tighten the bolts in the correct sequence to the first stage torque specification.
  • Re-check all the bolts to ensure they have reached the first stage torque specification.
  • Continue to the final torque specification in the correct sequence as per the repair manual.
  • Re-check all the bolts to ensure they have reached the final torque specification.
View full procedure
Technical Service Bulletins

AL551 Transmission Bolt Loosening Issue

2016-05-12

Some AL551 transmissions may experience bolt loosening due to vibration and thermal expansion. This bulletin outlines the inspection and re-torque procedure.

2012-2016

Resolution: Inspect all transmission housing and mechatronic unit bolts. Re-torque to specified values using a calibrated torque wrench and the correct sequence. Apply threadlocker if necessary, as directed in the repair manual. Check the bolt torque at regular intervals as outlined by the vehicle manufacturer.

Mechatronic Unit Bolt Torque Specification Update

2017-11-20

A revision to the torque specification for the mechatronic unit bolts on the AL551 transmission has been released. This bulletin supersedes prior specifications.

2012-2018

Resolution: Always refer to the latest repair manual or technical bulletin for the most up-to-date torque specifications for the mechatronic unit bolts. Follow the correct torque sequence during re-installation. Ensure the calibrated torque wrench is within its calibration period.

About the Author

Expert automotive knowledge and experience

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.

Facebook Contact
15+ Years
Experience
500+ Guides
Guides
50+ Makes
Vehicles
1000+ Solutions
Solutions

Diagnostic

Specialized in advanced diagnostic techniques using modern scan tools and oscilloscopes.

Repair

Expert in both traditional mechanical repairs and modern vehicle systems.

Additional Expertise

Documentation

Created over 500 detailed repair guides and technical documents.

Training

Conducted technical training sessions and contributed to repair databases.

Certifications & Research

Certifications

  • ASE Master Technician Certification
  • Advanced Diagnostic Specialist
  • Hybrid/Electric Vehicle Systems
  • Performance Tuning Expert

Research & Community

Actively researches emerging technologies and contributes to automotive forums.

Legal Disclaimer

Important information about using this content

Always refer to your vehicle's service manual and take appropriate safety precautions when performing any maintenance or repairs.

General Information
The information provided on this website is for general informational purposes only. While we strive to maintain accuracy in our content, all specifications, procedures, and technical information should be verified against your vehicle's official service manual or with the manufacturer directly.
Warranty & Liability

The content on this website is provided "as is" without any representations or warranties, express or implied. We make no representations or warranties regarding the accuracy, completeness, or availability of the information.

We shall not be liable for any direct, indirect, special, or consequential damages arising from the use of information on this website.

Technical Information
  • All specifications, including torque values, fluid capacities, and maintenance procedures, should be verified against your vehicle's factory service manual.
  • Vehicle specifications and procedures may vary by model year, trim level, and region.
  • Always follow the manufacturer's recommended procedures and safety precautions.
  • Working on vehicles can be dangerous. Always take proper safety precautions and use appropriate safety equipment.
  • If you're unsure about any procedure, consult a qualified professional mechanic.
Intellectual Property
All content, including text, images, and specifications, is protected by copyright and other intellectual property laws. Any unauthorized use or reproduction is prohibited.

© 2025 Audi Specs. All rights reserved.

Privacy Policy Terms of Service