BMW 745i 2020-present ZF 8HP Transmission Transmission Torque Specifications & Bolt Torque Values
BMW 745i 2020-present

BMW 745i 2020-present ZF 8HP Transmission Torque Specifications

Detailed torque specifications for all bolts associated with the ZF 8HP transmission in the 2020-Present BMW 745i (G11/G12) generation.

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 housing to the vehicle's chassis or subframe. Proper torque ensures correct alignment and support, preventing movement and vibration.

1

Transmission Mounting Bolts

M12 x 1.75
Torque Value
45 ft-lbs (61 N·m)
Important Notes
Ensure mating surfaces are clean. Tighten all mounting bolts evenly.

Transmission Oil Pan

These bolts secure the transmission oil pan to the transmission case. Proper torque is essential to prevent leaks from the pan gasket and maintain proper transmission fluid levels.

1

Transmission Oil Pan Bolts

M6 x 1.0
Torque Value
10 ft-lbs (13 N·m)
Important Notes
Use new gasket and follow the specified torque sequence. Tighten bolts in a criss-cross pattern.
2

Transmission Oil Pan Drain Plug

M14 x 1.5
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Use a new sealing washer on the drain plug. Do not over-tighten.

Fluid Plugs

These plugs seal the transmission fluid drain and fill ports. Proper torque ensures a tight seal, preventing fluid leaks.

1

Transmission Fluid Drain/Fill Plugs

M18 x 1.5
Torque Value
25 ft-lbs (34 N·m)
Important Notes
Use new sealing washers. Do not over-tighten these plugs.

Mechatronic Unit

These bolts secure the mechatronic unit (valve body) to the transmission case. Proper torque is crucial for correct sealing and function.

1

Mechatronic Unit Mounting Bolts

M6 x 1.0
Torque Value
6 ft-lbs (8 N·m)
Important Notes
Tighten in a criss-cross pattern. Do not over-tighten, as this can distort the mechatronic housing.
2

Valve Body Mounting Bolts

M6 x 1.0
Important Notes
Tighten bolts in a criss-cross pattern. Torque to 8 N·m.

Fluid Cooler Lines

These fittings secure the transmission oil cooler lines to the transmission housing. Proper torque is critical to prevent fluid leaks.

1

Transmission Fluid Cooler Line Fittings (Banjo Bolts)

M12 x 1.5
Torque Value
15 ft-lbs (20 N·m)
Important Notes
Use new sealing washers. Ensure banjo fitting is properly aligned.
2

Transmission Fluid Cooler Line Fittings (Threaded)

M16 x 1.5
Torque Value
18 ft-lbs (25 N·m)
Important Notes
Ensure fittings are properly threaded and aligned. Do not cross-thread

Torque Converter

These bolts attach the torque converter to the engine's flexplate. These are often Torque-To-Yield and must be torqued in sequence. Improper torque can cause vibration, imbalance and damage to the flexplate and transmission assembly.

1

Torque Converter Bolts

M10 x 1.25
Important Notes
Always use new torque converter bolts. Tighten in a star pattern. Angle is after initial torque value is reached. These are Torque to Yield Bolts.

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 crucial for the ZF 8HP transmission?

Accurate torque specifications are vital for the ZF 8HP transmission to ensure proper clamping force between components. Under-torquing can lead to loosening, leaks, and premature wear, while over-torquing can damage threads, distort parts, and cause component failure. For example, overtightening a valve body bolt could distort the housing, leading to improper valve operation and transmission malfunctions. Correct torque ensures that the transmission operates as intended without any issues related to loose or overly tight fasteners.

Q2

What happens if I don't use a torque wrench on the transmission bolts?

Without a torque wrench, it’s extremely difficult to achieve the correct torque on bolts. 'By feel' methods can lead to either under-torqued or over-torqued bolts. Under-torqued bolts can loosen over time, causing fluid leaks, vibration, and ultimately component failure. Over-torqued bolts can strip threads, crack housings, and damage internal components. For instance, over-tightening the pan bolts can lead to leaks and potentially a damaged pan.

Q3

Can I reuse the transmission bolts?

It is generally recommended to replace transmission bolts, especially those specified as 'torque-to-yield' or those securing critical components like the valve body or mechatronics unit. Reusing these bolts can compromise their strength and clamping capability, increasing the risk of failure. However, some bolts like those on the transmission housing might be reusable provided they are in good condition. Always consult the vehicle's specific repair manual or a trusted source for the manufacturer's recommendations.

Q4

What type of fluid should I use after servicing the transmission?

The ZF 8HP transmission in your 2020-Present BMW 745i requires a specific type of transmission fluid, typically a low-viscosity fluid designed to meet the ZF Lifeguard Fluid specifications. Using the incorrect fluid can lead to shift problems, overheating, premature wear of internal components and long term transmission failure. For best results, it's recommended to use the fluid specified by BMW (and sometimes by ZF, the manufacturer of the transmission), and follow the service procedures for fluid level adjustment.

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 accurate tightening of transmission bolts to specified values.

  • Wide torque range (suitable for low to high torque specs)
  • Clearly marked scale for easy reading
  • Click-type mechanism for precise tightening
Learn more

Torque Wrench (3/8" Drive)

A 3/8" drive torque wrench may be needed for smaller fasteners and areas with limited clearance.

  • Suitable for lower torque applications
  • Compact size for tight spaces
  • Accurate torque measurement
Learn more

Socket Set (Metric)

A comprehensive set of metric sockets is necessary to fit the various bolt heads on the ZF 8HP transmission.

  • Standard and deep socket depths
  • Sizes ranging from 8mm to 19mm (or larger)
  • Durable construction for high torque applications
Learn more

E-Torx Socket Set

E-Torx (external Torx) sockets are needed for some fasteners used on the ZF 8HP transmission.

  • Sizes ranging from E8 to E18
  • Durable construction
  • Precise fit to prevent damage
Learn more

Extension Bars

Extension bars will help reach recessed bolts or bolts with limited access.

  • Various lengths
  • Durable steel construction
  • Provide additional leverage
Learn more

Universal Joint

A universal joint will help access bolts at awkward angles.

  • Swiveling head
  • Durable steel construction
  • Allows for angled access
Learn more
Service Procedures

ZF 8HP Transmission Oil Pan Bolt Torque Procedure

This procedure outlines the proper method for torquing the oil pan bolts on a ZF 8HP transmission.

  • Clean the threads of the bolts and the bolt holes.
  • Install a new transmission oil pan gasket.
  • Install the transmission oil pan.
  • Install the bolts finger tight
  • Tighten the bolts in a star pattern to the initial torque specification.
  • Tighten the bolts in a star pattern to the final torque specification.
View full procedure

ZF 8HP Transmission Mechatronics Unit Bolt Torque Procedure

This procedure outlines the proper method for torquing the Mechatronics unit bolts on a ZF 8HP transmission.

  • Clean the threads of the bolts and the bolt holes.
  • Install a new mechatronics unit gasket.
  • Install the mechatronics unit.
  • Install the bolts finger tight.
  • Tighten the bolts in a star pattern to the initial torque specification.
  • Tighten the bolts in a star pattern to the final torque specification.
View full procedure

ZF 8HP Transmission Bell Housing Bolt Torque Procedure

This procedure outlines the proper method for torquing the bell housing bolts on a ZF 8HP transmission.

  • Clean the threads of the bolts and the bolt holes.
  • Position the transmission bell housing.
  • Install the bell housing bolts finger tight.
  • Tighten the bolts in a circular pattern to the initial torque specification.
  • Tighten the bolts in a circular pattern to the final torque specification.
View full procedure
Technical Service Bulletins

ZF 8HP Transmission Oil Leakage From Oil Pan

2021-05-15

Some 2020-2021 models equipped with the ZF 8HP transmission may experience oil leakage from the transmission oil pan due to incorrect tightening of the bolts.

2020-2021 BMW 745i

Resolution: Inspect the oil pan gasket for damage. Replace if necessary. Clean threads, and tighten the bolts to the updated torque specification of 10 Nm + 90°.

ZF 8HP Transmission Mechatronics Sealing Issues

2022-03-10

Some vehicles equipped with the ZF 8HP transmission may exhibit shifting issues related to mechatronics unit sealing issues. Improper torque can contribute to this.

2020-2022 BMW 745i

Resolution: Verify the correct Mechatronics unit bolt torque specification of 8 Nm + 90°. Replace gasket if necessary, clean surfaces and bolts before reassembly. Ensure proper bolt tightening sequence.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

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  • All specifications, including torque values, fluid capacities, and maintenance procedures, should be verified against your vehicle's factory service manual.
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