Buick LaCrosse 2017-2019 6T40 Transmission Transmission Torque Specifications & Bolt Torque Values
Buick LaCrosse 2017-2019

Buick LaCrosse 2017-2019 6T40 Transmission Torque Specifications

This page provides detailed torque specifications for all bolts related to the 6T40 transmission used in the 2017-2019 Buick LaCrosse. Includes case bolts, valve body bolts, pan bolts, and more.

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 Mounting

These specifications pertain to the bolts that secure the transmission assembly to the engine block and/or vehicle frame/subframe. Correct torque is essential for secure mounting and to prevent vibrations that could damage components.

1

Transmission Mounting Bolts

M12 x 1.75
Torque Value
37 ft-lbs (50 N·m)
Important Notes
Ensure threads are clean and lubricated. Use a calibrated torque wrench. Tighten in a cross pattern.

Transmission Case

This section covers bolts related to the external components of the transmission case, including the oil pan and side cover.

1

Transmission Oil Pan Bolts

M6 x 1.0
Torque Value
8.8 ft-lbs (12 N·m)
Important Notes
Tighten in a cross pattern. Overtightening can damage the pan or gasket leading to leaks.
2

Side Cover Bolts

M6 x 1.0
Torque Value
7.4 ft-lbs (10 N·m)
Important Notes
Ensure proper sealing surface. Tighten evenly to avoid leaks.

Fluid Plugs

These specifications are for the drain and fill plugs, which require proper torque for a leak-free seal.

1

Transmission Drain and Fill Plugs

M18 x 1.5
Torque Value
27 ft-lbs (37 N·m)
Important Notes
Ensure the sealing surface is clean and lubricated. Do not overtighten, which could damage the plug or threads.

Drivetrain

Bolts connecting the transmission to the drive axles/half shafts.

1

Drive Axle/Half Shaft Bolts

M10 x 1.5
Torque Value
118 ft-lbs (160 N·m)
Important Notes
These bolts connect the axle flange to the transmission output shaft. Ensure proper alignment during install. Apply Loctite if specified by vehicle manufacturer.

Tcm

These specifications relate to the mounting of the Transmission Control Module (TCM) onto the transmission case.

1

Transmission Control Module (TCM) Mounting Bolts

M5 x 0.8
Torque Value
7.4 in-lbs (10 N·m)
Important Notes
Handle the TCM with care. Overtightening can damage the module or its mounting points.

Bellhousing

These bolts secure the transmission bellhousing to the engine. Proper torque is essential for alignment and support.

1

Transmission Bellhousing Bolts

M12 x 1.75
Torque Value
37 ft-lbs (50 N·m)
Important Notes
Ensure the mating surfaces are clean before installation. Tighten in a cross pattern to ensure even pressure.

Valve Body

These specifications are for the bolts mounting the valve body inside the transmission. Precise torque is essential for proper operation.

1

Valve Body Mounting Bolts

M6 x 1.0
Torque Value
7 in-lbs (9 N·m)
Important Notes
Tighten bolts evenly in a cross pattern. Overtightening can damage the valve body or affect its function. It is recommended to check the specific service manual for your vehicle, as torque values can vary slightly between 6T40 transmissions.

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 the 6T40 transmission?

Using the correct torque specifications is critical to ensure proper clamping force and prevent damage to the transmission components. Over-tightening can strip threads or deform parts, leading to leaks or component failure. Under-tightening can cause fasteners to loosen over time, resulting in leaks, vibrations, and eventually, more severe damage. For example, a loose pan bolt could result in significant transmission fluid leaks and potential transmission damage due to lack of lubrication.

Q2

What happens if I over-torque the transmission pan bolts?

Over-torquing transmission pan bolts can crush the gasket, leading to leaks. It can also strip the threads in the transmission case or deform the pan itself, requiring costly repairs. You may notice fluid leaking from the pan area soon after the repair or have trouble sealing the pan during future servicing.

Q3

Can I reuse the transmission pan bolts?

Generally, it's recommended to replace transmission pan bolts, especially those with sealing washers or features, as they can lose their clamping force after being tightened. While reusing may seem cost effective, it increases the risk of future leaks and potential transmission problems. However, depending on the bolts, visual inspection can determine the possibility of re-use. If bolts appear undamaged, then they can be reused with proper torque.

Q4

Do I need to use any thread locker on the 6T40 transmission bolts?

Thread locker is usually not required on most 6T40 transmission fasteners. However, certain bolts, such as those connecting the torque converter to the flexplate, may specify thread locker. Always refer to the service manual for the specific application. If required, use a medium strength thread locker, such as Loctite 242.

Q5

Should I lubricate the transmission bolt threads before tightening?

No, unless otherwise specified in the service manual for your specific 2017-2019 Buick Lacrosse 6t40 transmission configuration, the bolts should not be lubricated. Lubricating the threads without adjusting the torque can lead to over-tightening and damage, since lubrication reduces friction.

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 tightening bolts to the manufacturer's specified torque values.

  • Accurate torque application
  • 1/2 inch drive for common transmission bolts
  • Ratcheting mechanism
Learn more

Torque Wrench (3/8 inch drive)

A smaller torque wrench for lower torque value applications in the transmission assembly.

  • Accurate torque application
  • 3/8 inch drive for smaller bolts and access
  • Ratcheting mechanism
Learn more

Socket Set (Metric)

A comprehensive set of metric sockets for various bolt sizes used in the 6T40 transmission.

  • Variety of sizes
  • 6-point design for optimal grip
  • Durable construction
Learn more

Extension Bars (Various lengths)

Extension bars to reach recessed bolts within the transmission housing.

  • Various lengths for optimal access
  • Durable construction
  • Secure connection
Learn more

Universal Joint

A universal joint to access bolts at angles.

  • Allows for angled access
  • Durable construction
  • Swivels for flexibility
Learn more
Service Procedures

6T40 Transmission Pan Bolt Torque Procedure

Procedure for tightening the transmission pan bolts to the correct torque specification.

  • Clean the mating surfaces of the transmission pan and transmission case.
  • Install the transmission pan and new gasket.
  • Install the transmission pan bolts by hand. Make sure the gasket is evenly seated.
  • Tighten the transmission pan bolts in a cross pattern sequence to 8-10 Nm (71-89 lb-in).
  • Verify the torque on all bolts once complete.
View full procedure

6T40 Transmission Control Valve Body Bolt Torque Procedure

Procedure for tightening the control valve body bolts to the correct torque specification.

  • Position the valve body against the transmission case.
  • Install the control valve body bolts by hand.
  • Tighten the bolts to 10 Nm (89 lb-in) in a sequence starting with the innermost bolts working outward.
  • Verify the torque on all bolts once complete.
View full procedure

6T40 Transmission Bellhousing Bolt Torque Procedure

Procedure for tightening the transmission bellhousing to the engine block bolts to the correct torque specification.

  • Position the transmission bellhousing to the engine block.
  • Install the bellhousing bolts by hand.
  • Tighten the transmission bellhousing to engine block bolts to 50 Nm (37 lb-ft).
  • Verify the torque on all bolts once complete.
View full procedure
Technical Service Bulletins

6T40 Transmission Fluid Leak Diagnosis

2018-03-15

This bulletin addresses potential fluid leaks from the 6T40 transmission, often stemming from improperly torqued pan bolts or other seals.

2017-2019 Buick LaCrosse

Resolution: Inspect for leaks, replace gasket, and properly torque all bolts according to service manual.

6T40 Transmission Valve Body Issues and Bolt Torque

2019-01-20

This bulletin details concerns with shift issues related to valve body bolts becoming loose over time. This can result in erratic transmission behavior.

2017-2019 Buick LaCrosse

Resolution: Inspect and ensure valve body bolts are tightened to the factory torque specification. Replace if needed and perform a transmission quick learn procedure after the service.

About the Author

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Alan Montanye - Automotive Technical Specialist
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Alan Montanye

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