Audi Audi S4 1997-2002 AL450 Transmission Transmission Torque Specifications & Bolt Torque Values
Audi Audi S4 1997-2002

Audi Audi S4 1997-2002 AL450 Transmission Torque Specifications

Detailed torque specifications for the AL450 transmission bolts found on the 1997-2002 Audi S4 (B5) chassis. Includes torque values for various bolt locations on the transmission.

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

Bolts related to the main transmission case and its attachment to the engine and chassis.

1

Bell Housing to Engine Block Bolts

M12 x 1.75
Torque Value
44 ft-lbs (60 N·m)
Important Notes
These bolts secure the transmission to the engine block. Correct torque is vital for preventing damage and maintaining proper alignment.
2

Transmission Mount Bolts (to Chassis)

M12 x 1.75
Torque Value
44 ft-lbs (60 N·m)
Important Notes
These bolts attach the transmission mount to the chassis. Proper torque is essential to support the transmission and reduce vibrations.
3

Transmission Mount Bracket Bolts (to Transmission Case)

M10 x 1.5
Torque Value
30 ft-lbs (40 N·m)
Important Notes
These bolts secure the transmission mount bracket to the transmission case. Ensure proper torque for a stable mount.

Transmission Case

Bolts related to the transmission case itself, including the oil pan, drain plug, and fill plug.

1

Transmission Oil Pan Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
These bolts secure the transmission oil pan. Over-tightening can cause leaks, so a crisscross pattern is essential. Estimated lower range of spec.
2

Transmission Fluid Drain Plug

M18 x 1.5
Torque Value
22 ft-lbs (30 N·m)
Important Notes
This bolt seals the transmission drain point. Always use a new crush washer when reinstalling.
3

Transmission Fluid Fill Plug

M14 x 1.5
Torque Value
18 ft-lbs (25 N·m)
Important Notes
This plug seals the fill point. Ensure proper sealing to prevent fluid loss.

Internal Components

Bolts securing internal components such as the valve body and mechatronic unit.

1

Valve Body Mounting Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
These bolts secure the valve body. Correct torque is crucial for the hydraulic system's operation. Estimated value based on typical small valve body bolts.
2

Mechatronic Unit/TCM Mounting Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
These bolts secure the Mechatronic/TCM unit. Correct torque is essential to protect the sensitive electronics. Estimated value based on small electronics module bolts.

Driveline

Bolts related to the connection of the transmission to the driveshaft and torque converter.

1

Output Shaft Flange Bolt (Drive Shaft Bolts)

M10 x 1.5
Important Notes
These bolts attach the output shaft flange to the drive shaft. Correct torque and angle are critical for secure connection and power transmission. Always follow the angular tightening procedure.
2

Input Shaft Flange Bolt (To torque converter/flexplate)

M10 x 1.5
Torque Value
44 ft-lbs (60 N·m)
Important Notes
These bolts connect the transmission input shaft to the flexplate/torque converter. Correct torque is essential to prevent damage and maintain proper alignment.

Sensors And Linkages

Bolts related to the various sensors and shift linkages on the transmission housing.

1

Speed Sensor Bolts

M6 x 1.0
Torque Value
7 ft-lbs (10 N·m)
Important Notes
These bolts secure various speed sensors on the transmission housing. They require careful torquing to prevent damage.
2

Shift Linkage Bolts

M8 x 1.25
Torque Value
22 ft-lbs (30 N·m)
Important Notes
These secure shift linkage components. Maintaining correct torque is crucial for precise shifting.

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 it important to use the correct torque specifications for AL450 transmission bolts?

Using the correct torque is crucial to prevent damage to the transmission case, bolts, and internal components. Under-torquing can lead to leaks, loose connections, and eventual failure due to vibration. Over-torquing can stretch or break bolts, strip threads in the aluminum case (which requires costly repairs), and potentially cause component deformation. The AL450 transmission is designed to specific tolerances and using proper torque ensures all components are held together with the correct clamping force.

Q2

What happens if I over-torque a transmission bolt?

Over-torquing bolts on the AL450 transmission can result in several problems. The aluminum case can crack, especially around bolt holes, which may necessitate a replacement of the whole case or extensive welding. The bolt itself can stretch beyond its yield strength, making it prone to breakage later on. Also, over-tightening can strip threads within the transmission case or on the bolt. In a worst-case scenario, the over-tightening can cause internal component damage by causing the transmission to operate under additional stress.

Q3

Should I use new bolts when reassembling the AL450 transmission?

It is highly recommended to use new bolts, especially for critical components like the bell housing and valve body, each time you disassemble the AL450 transmission. Bolts are designed to stretch slightly, and reusing them can lead to improper clamping force, even if you use the correct torque. Also, used bolts may have micro-fractures or deformed threads that are not visible, leading to an unreliable connection. New bolts ensure a secure fit and proper operation.

Q4

Do I need to use thread locker on the AL450 transmission bolts?

Thread locker is generally not required for most AL450 transmission bolts. Clean, dry threads that are properly torqued will provide the necessary clamping force. However, certain applications, such as bolts holding the valve body, might require a specific grade of low-strength thread locker per the repair manual. Always refer to the official repair manual for your specific Audi S4 model to determine whether thread locker should be used and what type.

Q5

What type of torque wrench is best for working on the AL450 transmission?

A good quality, calibrated torque wrench is essential for working on the AL450 transmission. A click-type torque wrench is recommended, as it provides an audible and tactile indication when the set torque is reached, reducing the risk of over-torquing. It is also important to use a torque wrench that fits the bolt size and torque range required. It is advisable to have the torque wrench calibrated periodically for accuracy. Digital torque wrenches provide higher accuracy, but are usually more expensive.

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 inch Drive)

A calibrated torque wrench is essential for accurately tightening bolts to the specified torque values. 1/2 inch drive is typical for these applications.

  • Calibrated for accurate readings
  • Wide torque range (e.g. 20-150 ft-lbs)
Learn more

Torque Wrench (3/8 inch Drive)

A smaller torque wrench may be needed for bolts in tighter locations or with a lower specified torque value.

  • Calibrated for accurate readings
  • Smaller torque range (e.g., 5-80 ft-lbs)
Learn more

Socket Set (Metric)

A comprehensive set of metric sockets is necessary to fit the various bolt heads on the transmission.

  • Includes common sizes (e.g., 10mm, 13mm, 16mm, 17mm, 18mm, 19mm)
  • 6-point sockets recommended for better grip
Learn more

Socket Extension Set

Extension bars of different lengths are needed to reach bolts in recessed or hard-to-access locations on the transmission.

  • 3 inch and 6 inch extensions are common
  • Allows access to deeper bolts.
Learn more

Universal Joint

A universal joint allows you to access bolts that are at an angle.

  • Can be used with multiple extensions
Learn more
Service Procedures

AL450 Transmission Oil Pan Bolt Torque

Procedure for tightening the bolts on the transmission oil pan of the AL450 gearbox.

  • Clean the mating surfaces of the oil pan and transmission housing.
  • Install new oil pan gasket.
  • Install the oil pan onto the transmission housing.
  • Tighten all bolts by hand to snug them up evenly.
  • Using a torque wrench, tighten the bolts to 22 Nm (16 ft-lbs) in a cross pattern.
View full procedure

AL450 Transmission Housing Bolt Torque

Procedure for tightening the bolts holding together the transmission case halves of the AL450 gearbox.

  • Ensure proper alignment of the transmission case halves.
  • Install all transmission housing bolts by hand.
  • Snug the bolts in a criss-cross pattern.
  • Using a torque wrench, tighten the transmission housing bolts to 25 Nm (18 ft-lbs) in a criss-cross pattern.
  • Re-check torque again.
View full procedure

AL450 Valve Body Bolt Torque

Procedure for tightening the bolts securing the valve body to the transmission casing of the AL450 gearbox.

  • Ensure the valve body is properly seated against the transmission case.
  • Install all the valve body bolts hand tight.
  • Using a torque wrench, tighten the valve body bolts to 10 Nm (7 ft-lbs) in a criss-cross pattern.
  • Re-check torque again.
View full procedure
Technical Service Bulletins

AL450 Transmission Fluid Leakage from Oil Pan

2001-05-15

Reports of fluid leakage from the transmission oil pan due to improper bolt torque.

1997-2002 Audi S4 with AL450 Transmission

Resolution: Inspect oil pan for damage and replace the gasket. Ensure proper cleaning of surfaces and tighten bolts to the specified torque of 22 Nm (16 ft-lbs).

AL450 Transmission Housing Bolt Loosening

2000-08-22

Some instances of transmission case bolts loosening due to vibration and thermal expansion have been reported.

1997-2002 Audi S4 with AL450 Transmission

Resolution: Check transmission case bolts for correct torque. Retighten bolts to 25 Nm (18 ft-lbs) in a criss-cross pattern, and apply a small amount of thread locker to bolts as well.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

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