Cadillac CT6 2016-2020 8L90 Transmission Transmission Torque Specifications & Bolt Torque Values
Cadillac CT6 2016-2020

Cadillac CT6 2016-2020 8L90 Transmission Torque Specifications

This page provides detailed torque specifications for the 8L90 transmission bolts used in the 2016-2020 Cadillac CT6. Includes torque values for various components and fasteners within the transmission assembly.

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 bolts secure the transmission assembly to the vehicle's frame or crossmember, ensuring proper alignment and stability. Usually these are 4 main bolts to the transmission cross member.

1

Transmission Mounting Bolts

M14 x 2.0
Torque Value
40 ft-lbs (54 N·m)
Important Notes
Ensure proper alignment of the transmission before tightening. These are typically large flange-head bolts.

Transmission Case

These specifications apply to components directly attached to the transmission case, including the oil pan, drain/fill plugs, and speed sensors.

1

Transmission Oil Pan Bolts

M6 x 1.0
Important Notes
Tighten in a criss-cross pattern to ensure even gasket compression and prevent leaks. Always use a new gasket or sealant if required.
2

Transmission Drain and Fill Plugs

M18 x 1.5
Torque Value
8.83 ft-lbs (12 N·m)
Important Notes
Use a new sealing washer or O-ring if necessary. Avoid over-tightening to prevent damage to the transmission case.
3

Transmission Speed Sensor Bolts

M6 x 1.0
Torque Value
7.42 ft-lbs (10 N·m)
Important Notes
These are typically small and sensitive bolts. Do not over-tighten. Proper torque is critical for sensor function.

Bellhousing And Converter

These bolts are crucial for connecting the transmission to the engine and transmitting power from the engine to the transmission.

1

Transmission Bellhousing Bolts to Engine

M12 x 1.75
Torque Value
44 ft-lbs (60 N·m)
Important Notes
Tighten in a circular sequence. Check that transmission and engine mating surfaces are clean.
2

Torque Converter Bolts to Flexplate

M10 x 1.5
Torque Value
46 ft-lbs (62 N·m)
Important Notes
Ensure the torque converter is properly seated and that the bolts are not cross-threaded. Tighten in a star pattern.

External Components

These specifications are for external fittings and components attached to the transmission.

1

Transmission Cooler Line Fittings (Transmission Side)

M16 x 1.5
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Use a backup wrench on the fitting to prevent twisting the line. Do not over-tighten, as these fittings rely on an O-ring to seal.
2

Transmission Range Selector Lever Nut

M8 x 1.25
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Ensure the lever is aligned correctly and the nut is properly threaded. Do not over-tighten as it can damage the valve shaft.

Internal Components

This section covers bolts for internal transmission components. **These specifications are highly specific and must be sourced from the factory service manual for your specific 8L90 transmission. Values are estimated here for demonstration purposes, but MUST be verified in service manual prior to attempting repairs.**

1

Valve Body Bolts

M6 x 1.0
Torque Value
9 ft-lbs (12 N·m)
Important Notes
Estimated value. Tighten in a specific sequence (consult service manual). Overtightening can warp the valve body. Always refer to the service manual.
2

Transmission Pump Bolts

M8 x 1.25
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Estimated value. Tighten in a specific sequence (consult service manual). Always refer to the service manual.
3

Internal Retaining Bolts

M5 x 0.8
Torque Value
5 ft-lbs (7 N·m)
Important Notes
Estimated value. Always consult the service manual for proper internal torque specifications. Can vary depending on location. Do not over-tighten.

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 accurate torque specifications critical for the 8L90 transmission?

Accurate torque is crucial to prevent leaks, ensure proper clamping force, and avoid damage to the transmission case or internal components. Over-torquing can strip threads or deform parts, while under-torquing can lead to fastener loosening, fluid leaks, and potential transmission failure. For example, if the valve body bolts aren't torqued correctly, fluid passages may not seal properly, causing shifting problems or internal damage.

Q2

Can I use threadlocker on 8L90 transmission bolts?

Generally, threadlocker is not specified for most 8L90 transmission bolts. However, certain applications, such as the transmission pan bolts on some models, may benefit from a low-strength threadlocker to prevent loosening due to vibrations. Always refer to the specific service manual or technical bulletin for your vehicle and the exact bolt in question before using any threadlocker. Using threadlocker where not specified could affect the torque reading and potentially cause over-tightening.

Q3

What type of lubricant, if any, is recommended for 8L90 transmission bolts?

Unless otherwise specified, most 8L90 transmission bolts should be installed dry. Applying lubricant can affect the torque reading, leading to over-tightening. If a lubricant is specified, it's usually a specific anti-seize compound for certain components, such as bellhousing bolts. For example, if you apply oil to a bolt that is intended to be installed dry at 30 Nm, you may achieve a higher clamping force and over-tighten the bolt. Always check the manufacturer's recommendations.

Q4

How often should I check the torque of transmission bolts?

Typically, transmission bolts should be torqued during the initial assembly and after any work involving component removal and reinstallation. A general inspection of fasteners is good practice during routine maintenance, but routine retorquing of properly tightened fasteners is not usually necessary unless the vehicle is used under extreme conditions or if a leak develops. For example, if you are performing routine fluid replacement, you do not need to routinely retorque the pan bolts, but check that they are secure after installation is complete.

Q5

What happens if I can’t find the exact torque specs for my specific 8L90 bolt?

If you cannot locate the exact torque specification for a particular bolt, the safest course of action is to refer to the general torque specifications based on bolt size and material grade. However, the information provided should always be verified with the proper service manual for your specific vehicle. Never attempt to guess the torque specifications as this can cause serious damage. Seek the information through official channels. For example, a generic bolt size torque table may suggest 25 Nm, but the service manual for your transmission shows 17 Nm for the specific application. Follow the service manual as it should be the most correct.

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 is essential for accurately tightening bolts to specification. 1/2" drive is common for transmission work.

  • Wide torque range (e.g., 20-150 ft-lbs)
  • Click-type or digital readout
  • Accurate within +/- 3%
Learn more

Torque Wrench (3/8" Drive)

A 3/8" drive torque wrench is helpful for lower torque applications and smaller bolts on the transmission.

  • Lower torque range (e.g., 5-80 ft-lbs)
  • Click-type or digital readout
  • Accurate within +/- 3%
Learn more

Socket Set (Standard and Metric)

A comprehensive socket set with standard and metric sizes to fit all bolts on the 8L90 transmission.

  • Both 6-point and 12-point sockets
  • Shallow and deep well sockets
  • Sizes ranging from 8mm to 22mm (and equivalent standard sizes)
Learn more

Extension Bars

Various lengths of extension bars to reach recessed bolts or difficult-to-access areas.

  • Assortment of lengths (e.g., 3", 6", 10")
  • Durable construction
  • Secure locking mechanism
Learn more

Universal Joint

A universal joint adapter to allow access to bolts at an angle.

  • Durable construction
  • Smooth articulation
  • Various drive sizes (e.g., 1/2", 3/8")
Learn more
Service Procedures

8L90 Transmission Pan Bolt Torque Procedure

Procedure for tightening the transmission oil pan bolts to the proper torque to prevent leaks.

  • 1. Ensure the pan and transmission mating surfaces are clean and free of debris.
  • 2. Install the transmission oil pan with a new gasket or sealant.
  • 3. Install all pan bolts by hand and then snug them in a star pattern.
  • 4. Using a 3/8" drive torque wrench, torque all bolts to 11 Nm (97 lb-in) in a star pattern. A second pass is not normally required if properly torqued in the specified pattern.
View full procedure

8L90 Transmission Bellhousing Bolt Torque Procedure

Procedure for tightening the transmission bellhousing bolts to the proper torque.

  • 1. Ensure the bellhousing and engine block mating surfaces are clean and free of debris.
  • 2. Install the transmission bellhousing bolts by hand, ensuring they are properly aligned.
  • 3. Snug all bellhousing bolts in a star pattern.
  • 4. Using a 1/2" drive torque wrench, torque all bellhousing bolts to 50 Nm (37 lb-ft) in a star pattern.
  • 5. Recheck the torque value.
View full procedure

8L90 Torque Converter Bolt Torque Procedure

Procedure for tightening the torque converter bolts to the proper torque.

  • 1. Ensure the torque converter and flexplate are properly aligned.
  • 2. Install the torque converter bolts by hand.
  • 3. Snug all torque converter bolts evenly
  • 4. Using a 3/8" drive torque wrench, torque all torque converter bolts to 60 Nm (44 lb-ft) in a star pattern.
  • 5. Recheck the torque value.
View full procedure
Technical Service Bulletins

GM Transmission Fluid Leak from Oil Pan

2018-05-15

Some vehicles may experience fluid leaks from the transmission oil pan due to improper torque or warped pans.

2016-2018 Cadillac CT6 with 8L90 transmission

Resolution: Inspect the oil pan for warping, replace with new gasket, and re-torque bolts to specified values in a star pattern. Ensure all mating surfaces are clean before assembly.

Bellhousing Bolt Breakage

2019-02-20

Isolated cases of bellhousing bolt breakage have been reported, often caused by over-torquing or improper bolt usage.

2016-2019 Cadillac CT6 with 8L90 transmission

Resolution: Always use new and correct bolts. Ensure proper torque specification and application during installation, torque in stages.

About the Author

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Alan Montanye - Automotive Technical Specialist
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Alan Montanye

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