GMC Jimmy 1970-1991 TH350 Transmission Transmission Torque Specifications & Bolt Torque Values
GMC Jimmy 1970-1991

GMC Jimmy 1970-1991 TH350 Transmission Torque Specifications

Detailed torque specifications for the TH350 transmission bolts in 1970-1991 GMC Jimmy models. Includes pan bolts, bellhousing bolts, and other critical fasteners.

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

Bolts and components that secure the transmission to the crossmember or frame, ensuring proper alignment and stability.

1

Transmission Mounting Bolts

M10 x 1.5
Torque Value
40 ft-lbs (54 N·m)
Important Notes
Ensure crossmember is properly aligned before tightening.

Oil Pan

Bolts and components that secure the transmission oil pan to the transmission case, ensuring a proper seal to prevent leaks.

1

Transmission Oil Pan Bolts

M6 x 1.0
Torque Value
13 ft-lbs (18 N·m)
Important Notes
Use a new gasket and ensure the pan surface is clean.

Fluid Plugs

Plugs that allow for fluid drainage and refilling, ensuring proper fluid levels and preventing leaks.

1

Transmission Drain Plug

M12 x 1.75
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Ensure the plug is properly sealed to prevent leaks.
2

Transmission Fill Plug

M12 x 1.75
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Ensure the plug is properly sealed to prevent leaks.

Flywheel

Bolts that secure the flywheel to the crankshaft, ensuring proper engagement with the torque converter.

1

Flywheel Bolts

M10 x 1.25
Torque Value
63 ft-lbs (85 N·m)
Important Notes
Ensure the flywheel is properly aligned with the crankshaft.

Torque Converter

Bolts that secure the torque converter to the flexplate, ensuring proper alignment and engagement.

1

Torque Converter Bolts

M8 x 1.25
Torque Value
40 ft-lbs (54 N·m)
Important Notes
Ensure the torque converter is properly seated before tightening.

Bell Housing

Bolts that secure the transmission bell housing to the engine block, ensuring proper alignment and sealing.

1

Bell Housing Bolts

M10 x 1.5
Torque Value
40 ft-lbs (54 N·m)
Important Notes
Ensure the bell housing is properly aligned with the engine block.

Shift Linkage

Bolts that secure the shift linkage to the transmission, ensuring smooth and accurate shifting.

1

Shift Linkage Bolts

M6 x 1.0
Torque Value
13 ft-lbs (18 N·m)
Important Notes
Ensure the linkage is properly aligned before tightening.

Cooler Lines

Fittings that secure the transmission cooler lines to the transmission, ensuring proper fluid flow and preventing leaks.

1

Transmission Cooler Line Fittings

M12 x 1.5
Torque Value
18 ft-lbs (24 N·m)
Important Notes
Ensure the fittings are properly sealed to prevent leaks.

Tail Housing

Bolts that secure the tail housing to the transmission case, ensuring proper alignment and sealing.

1

Tail Housing Bolts

M8 x 1.25
Torque Value
30 ft-lbs (41 N·m)
Important Notes
Ensure the tail housing is properly aligned with the transmission case.

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 are the torque specifications for the TH350 transmission pan bolts?

The torque specification for the TH350 transmission pan bolts is 12-15 ft-lbs. Over-tightening can damage the pan or gasket, leading to leaks. Always use a torque wrench for accuracy.

Q2

How often should I check the torque on my TH350 transmission bolts?

It's recommended to check the torque on TH350 transmission bolts during routine maintenance, such as fluid changes or every 30,000 miles. Inspect for leaks or loose bolts, as vibrations can cause them to loosen over time.

Q3

Can I reuse the transmission pan gasket on my TH350?

Reusing the gasket is not recommended. Always replace the gasket when removing the pan to ensure a proper seal. A new gasket prevents leaks and maintains proper transmission pressure.

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

A precision tool used to apply a specific torque to bolts and nuts.

  • Adjustable torque settings
  • Durable construction for heavy-duty use
Learn more

Socket Set

A set of sockets in various sizes to fit transmission bolts.

  • Includes both metric and standard sizes
  • Compatible with torque wrenches
Learn more

Thread Locker

A chemical compound used to secure bolts and prevent loosening.

  • High-strength formula
  • Resistant to vibration and heat
Learn more
Service Procedures

TH350 Transmission Bolt Torque Specifications

Detailed steps to properly torque the bolts on a TH350 transmission.

  • Ensure the transmission is securely mounted on a workbench or vehicle.
  • Clean all bolt threads and mating surfaces to remove debris and old thread locker.
  • Apply a small amount of thread locker to the bolt threads.
  • Hand-tighten all bolts to ensure proper alignment.
  • Using a torque wrench, tighten the bolts to the specified torque values: 35-45 ft-lbs for case bolts, 15-20 ft-lbs for pan bolts, and 70-90 ft-lbs for bellhousing bolts.
  • Double-check all bolts to ensure they are properly torqued.
View full procedure
Technical Service Bulletins

TH350 Transmission Bolt Loosening Issue

1985-07-15

Reports of bolts loosening over time due to insufficient torque or lack of thread locker.

1970-1991 GMC Jimmy

Resolution: Ensure bolts are torqued to the correct specifications and use a high-strength thread locker during assembly.

TH350 Transmission Case Cracking

1988-03-22

Cracks in the transmission case due to over-torquing of bolts.

1970-1991 GMC Jimmy

Resolution: Follow the recommended torque specifications and avoid exceeding the maximum torque values.

About the Author

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Alan Montanye - Automotive Technical Specialist
ASE

Alan Montanye

Automotive Technical Specialist

ASE Master Certified Technician with over a decade of hands-on experience in automotive repair and diagnostics.

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