Audi Audi S4 1991-1994 VL300 Transmission Transmission Torque Specifications & Bolt Torque Values
Audi Audi S4 1991-1994

Audi Audi S4 1991-1994 VL300 Transmission Torque Specifications

Detailed torque specifications for all bolts on the VL300 manual transmission found in the 1991-1994 Audi S4 (C4) model, including case, bellhousing, and 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

Transmission Housing

Bolts securing the main transmission case halves together. Proper torque is crucial for a tight seal, preventing fluid leaks and maintaining structural integrity. Includes case bolts and other external housing bolts.

1

Main Case Bolts

M12 x 1.75
Torque Value
37 ft-lbs (50 N·m)
Important Notes
Estimated based on common values for aluminum transmission cases and bolts of similar sizes. Use a cross pattern and multiple passes to ensure even clamping pressure.

Transmission Mounting

Bolts associated with mounting the transmission to the vehicle's chassis. Proper torque is critical for vibration damping and drivetrain stability.

1

Transmission Mount Bolts

M12 x 1.75
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Bolts connecting the transmission mount to the vehicle's crossmember. Typically hardened bolts.
2

Starter Mounting Bolts (Transmission side)

M10 x 1.5
Torque Value
33 ft-lbs (45 N·m)
Important Notes
Secures the starter motor to the transmission bellhousing. Ensure proper alignment before tightening.

Output Shaft

Bolts associated with the transmission output shaft and related components. Proper torque is essential for secure power transfer and preventing vibrations.

1

Output Shaft Flange Bolts

M10 x 1.5
Torque Value
40 ft-lbs (54 N·m)
Important Notes
Bolts secure the output shaft flanges to the transmission output shafts.

Input Shaft

Bolts related to the input shaft housing. Correct torque prevents leaks and bearing misalignment.

1

Input Shaft Housing Bolts

M8 x 1.25
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Estimated based on similar applications within other Audi transmissions of the time. Use a cross pattern and multiple passes to ensure even clamping pressure.

Differential Housing

Bolts securing the differential housing to the transmission case. Proper torque maintains gear meshing and oil seals.

1

Differential Housing Bolts

M10 x 1.5
Torque Value
30 ft-lbs (40 N·m)
Important Notes
Estimated; industry standard for aluminum differential housings. Ensure proper alignment.

Fluid Plugs

Bolts used for fluid drain and fill, often with sealing washers. Correct torque prevents leaks.

1

Drain Plug

M18 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Industry standard for drain plug with sealing washer.
2

Fill Plug

M18 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Industry standard for fill plug with sealing washer.

Oil Pump

Bolts associated with the transmission oil pump. Proper torque is crucial for pump performance and preventing oil leaks.

1

Oil Pump Bolts

M6 x 1.0
Torque Value
8 ft-lbs (11 N·m)
Important Notes
Estimated; based on pump mounting bolts of similar sizes and applications.

Valve Body

Bolts securing the valve body to the transmission case. Accurate torque is crucial for proper valve operation and preventing leaks.

1

Valve Body Mounting Bolts

M6 x 1.0
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Estimated; based on general torque values for valve body mounting bolts. Ensure even pressure when tightening these small bolts.

Sensor Mounting

Small bolts securing speed and other sensors to the transmission casing. Proper torque ensures a secure mounting and accurate readings.

1

Speed Sensor Mounting Bolts

M6 x 1.0
Torque Value
7 ft-lbs (9.5 N·m)
Important Notes
Estimated; based on standard small sensor mounting bolts. Do not overtighten.

Bellhousing

Bolts securing the transmission bellhousing to the engine block. These bolts are critical for aligning the engine and transmission. Follow torque sequence to ensure proper alignment.

1

Bellhousing to Engine Bolts

M12 x 1.75
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Similar year/similar model; critical fastener torque spec. Follow a staggered torque pattern.

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 happens if I over-torque the transmission bolts?

Over-torquing can stretch or break the bolts, damage the transmission case threads, or crush the gasket, leading to leaks, potential component failure, and costly repairs. It's critical to use a calibrated torque wrench and adhere to the specified torque values. For example, overtightening the bell housing bolts can crack the aluminum housing.

Q2

What happens if I under-torque the transmission bolts?

Under-torquing will result in an insufficient clamping force, potentially causing bolts to loosen over time due to vibration. This can lead to leaks, misalignment of components, and eventual damage to the transmission. For example, under-torquing the output flange bolts could cause play and ultimately damage the output shaft.

Q3

Should I use new bolts when reassembling the transmission?

It is highly recommended to use new bolts, especially torque-to-yield (TTY) bolts if applicable. These bolts are designed for a one-time use and stretch during tightening. Reusing them can compromise their clamping force and lead to failure. While not every bolt on the VL300 is TTY, many are critical, such as the bellhousing to block bolts.

Q4

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

Thread locker, such as Loctite, is often recommended on specific bolts, especially those subject to vibration. Consult the repair manual for the 1991-1994 Audi S4 for specific locations requiring thread locker. Usually, the bolts that attach to the output shaft and drive flanges should have a medium strength thread locker applied to them.

Q5

What is the importance of the correct tightening sequence?

The correct tightening sequence ensures even pressure is applied to the components being bolted together. Inconsistent tightening can cause distortion, stress, and leaks. For the VL300, following the recommended sequence, often in a cross-pattern, prevents stress on the case and ensures proper component alignment. A good example is the bell housing to the engine block, you should move back and forth between the bolts to evenly apply clamping pressure.

Q6

How often should I check the transmission bolt torque?

Generally, it's recommended to check the torque on critical transmission bolts after an initial break-in period (e.g., after 500-1000 miles) following a major repair or overhaul. Subsequently, periodic checks (e.g., during regular maintenance) can help ensure proper clamping force and prevent potential issues. Extreme operating conditions may require more frequent checks.

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 1/2" drive torque wrench capable of measuring torque values from 20 Nm to 120 Nm. Essential for applying the correct torque to transmission bolts.

  • Accurate torque measurement
  • Audible click when torque is reached
  • Reversible ratchet mechanism
Learn more

Torque Wrench (3/8" Drive)

A 3/8" drive torque wrench for smaller bolts and accessing tighter spots. Must have a range of 10-50 Nm.

  • Accurate torque measurement
  • Smaller and more maneuverable
  • Audible click
Learn more

Socket Set (Metric)

A comprehensive metric socket set with a range from 10mm to 19mm, including various extensions and universal joints. Needed to reach all transmission bolts.

  • Standard and deep sockets
  • Variety of sizes for all bolts
  • Durable construction
Learn more

Extension Bars

Various length extension bars to reach recessed bolts and fasteners.

  • Available in different lengths
  • Ensures access to hard-to-reach bolts
  • Durable build quality
Learn more

Universal Joint

A universal joint to allow sockets to turn at an angle when needed for hard to reach bolts

  • Allows torque application from different angles
  • Durable and smooth operation
  • 1/2" or 3/8" sizes available
Learn more
Service Procedures

VL300 Transmission Bellhousing Bolt Torque Procedure

This procedure outlines the correct steps to torque the bellhousing bolts on the VL300 transmission.

  • Clean threads of all bolts and the bolt holes in the transmission and engine block.
  • Install the bellhousing bolts by hand, ensuring they are evenly tightened against the engine.
  • Using a 1/2" drive torque wrench, torque the bellhousing bolts in a star pattern to 45 Nm.
  • After torquing to 45 Nm, complete a final torque sequence at 60 Nm with the same star pattern.
  • Ensure all bolts are torqued to 60 Nm
  • Visually inspect the bolted connection for any gaps or irregularities.
View full procedure

VL300 Transmission Mount Bolt Torque Procedure

This procedure outlines the correct steps to torque the transmission mount bolts on the VL300 transmission.

  • Install transmission mount bolts by hand. Ensuring they are evenly tightened against the transmission and chassis
  • Using a 3/8" drive torque wrench, torque the transmission mount bolts to 25 Nm.
  • Visually inspect the bolted connection for any gaps or irregularities.
View full procedure

VL300 Output Flange Bolt Torque Procedure

This procedure outlines the correct steps to torque the output flange bolts on the VL300 transmission.

  • Install output flange bolts by hand. Ensure they are evenly tightened against the transmission and drive shaft flange
  • Using a 3/8" drive torque wrench, torque the output flange bolts to 30 Nm.
  • Visually inspect the bolted connection for any gaps or irregularities.
View full procedure
Technical Service Bulletins

Incorrect Bellhousing Bolt Torque Leads to Premature Transmission Wear

1994-05-15

A number of instances of premature transmission wear were reported as a result of insufficient torque on the bellhousing bolts. This bulletin outlines the specific torque procedure to prevent issues.

1991-1994 Audi S4

Resolution: Torque bellhousing bolts to 45 Nm initially in a star pattern, followed by a second pass at 60 Nm also in a star pattern. Always use a calibrated torque wrench and new bolts if available.

Transmission Mount Bolt Loosening Issues

1993-11-20

Reports of transmission mount bolts loosening over time have been identified as a potential safety issue. This bulletin outlines the proper tightening procedure.

1991-1994 Audi S4

Resolution: Ensure the transmission mount bolts are torqued to 25 Nm. Use thread locking compound if bolts show sign of loosening. Check torque values during routine maintenance.

About the Author

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Alan Montanye - Automotive Technical Specialist
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Alan Montanye

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