GMC Jimmy 1970-1991 TH400 Transmission Specifications
This document provides a detailed overview of the TH400 transmission specifications for the 1970-1991 GMC Jimmy. It includes critical technical details such as gear ratios, torque capacity, fluid requirements, and compatibility with various engine configurations. Designed to assist automotive enthusiasts, mechanics, and restorers, this guide ensures accurate understanding and application of the TH400 transmission in the GMC Jimmy. Whether for maintenance, repair, or performance upgrades, this resource offers valuable insights into the transmission's design and functionality, helping users optimize their vehicle's performance and longevity.
Overview Specifications
This document provides detailed specifications and information about the TH400 transmission used in the 1970-1991 GMC Jimmy. It is designed to assist enthusiasts, mechanics, and collectors in understanding the technical aspects, maintenance, and performance of this transmission. Use the search and navigation instructions to quickly find relevant sections and details. The document is divided into major sections, each focusing on a specific aspect of the TH400 transmission.
How to Use
Use the search functionality to quickly locate specific terms or phrases within the document. Enter keywords related to the TH400 transmission, such as 'torque converter' or 'gear ratios', to find relevant information.
Navigate through the document using the section titles and descriptions. Each major section is divided into subsections with detailed points. Click on a section or subsection to jump directly to the desired information.
Key Specifications
Transmission Type
3-speed automatic
Maximum Torque
450 lb-ft
First Gear Ratio
2.48:1
Second Gear Ratio
1.48:1
Third Gear Ratio
1.00:1
Available Specifications
General Specifications
This section covers the basic technical specifications of the TH400 transmission, including its design, construction, and compatibility with the 1970-1991 GMC Jimmy. It provides an overview of the transmission's key features and capabilities.
General Specifications
This section covers the basic technical specifications of the TH400 transmission, including its design, construction, and compatibility with the 1970-1991 GMC Jimmy. It provides an overview of the transmission's key features and capabilities.
Design and Construction
- 3-speed automatic transmission
- Heavy-duty cast iron case
- Torque converter lock-up feature
- Hydraulic control system
- Designed for high torque applications
- Compatible with 4x4 drivetrains
Compatibility
- Fits 1970-1991 GMC Jimmy models
- Compatible with V8 engines
- Requires specific bell housing
- Adaptable to various transfer cases
- Wide range of aftermarket support
Performance and Capabilities
This section delves into the performance characteristics of the TH400 transmission, including its torque handling, gear ratios, and overall durability. It highlights why the TH400 is considered a robust and reliable transmission.
Performance and Capabilities
This section delves into the performance characteristics of the TH400 transmission, including its torque handling, gear ratios, and overall durability. It highlights why the TH400 is considered a robust and reliable transmission.
Torque Handling
- Maximum torque capacity: 450 lb-ft
- Suitable for heavy towing and off-roading
- Strong planetary gear set
- Heavy-duty clutch packs
- High-capacity oil pump
Gear Ratios
- First gear: 2.48:1
- Second gear: 1.48:1
- Third gear: 1.00:1
- Reverse gear: 2.08:1
- Wide gear spread for versatility
Maintenance and Troubleshooting
This section provides guidance on maintaining the TH400 transmission and troubleshooting common issues. It includes tips for fluid changes, inspections, and diagnosing problems to ensure long-term reliability.
Maintenance and Troubleshooting
This section provides guidance on maintaining the TH400 transmission and troubleshooting common issues. It includes tips for fluid changes, inspections, and diagnosing problems to ensure long-term reliability.
Routine Maintenance
- Regular fluid and filter changes every 30,000 miles
- Use Dexron III or equivalent transmission fluid
- Inspect for leaks and wear periodically
- Check and adjust shift linkage
- Monitor transmission temperature
Common Issues
- Delayed or harsh shifts
- Transmission slipping
- Fluid leaks from seals or gaskets
- Overheating due to heavy loads
- Noisy operation indicating wear
Search Specifications
Search by specification name, value, or description
Type to search through torque specifications. Results will appear below as you type.
Transmission Specifications
Overview
- Type
- Automatic
- Configuration
- 3-speed
- Platform
- GM Turbo Hydra-Matic
- Material
- Cast iron case
- Location
- Rear-wheel drive
Dimensions
- Length
- 28.5 inches (724 mm)
- Width
- 16.2 inches (411 mm)
- Height
- 12.8 inches (325 mm)
- Weight
- 135 lbs (61.2 kg)
- input Shaft Length
- 7.5 inches (190.5 mm)
- Output Shaft Length
- 6.8 inches (172.7 mm)
- Bolt Pattern Diameter
- 12.6 inches (320 mm)
Materials
- Case
- Cast iron
- Gears
- Hardened steel
- Clutch Plates
- Composite friction material
- input Shaft
- High-strength alloy steel
- Oil Pan
- Aluminum
Features
- Performance
-
- Heavy-duty design for high torque applications
- Wide gear ratios for better acceleration
- Robust construction for durability
- Control
-
- Hydraulic shift control
- Manual shift option
- Integrated governor for smooth shifting
- Cooling
-
- Built-in transmission cooler
- High-capacity oil pump
- Efficient heat dissipation design
- Compatibility
-
- Fits GM V8 engines
- Supports various transfer cases
- Adaptable to different rear axle ratios
- Reliability
-
- Proven track record in off-road conditions
- Resistant to wear and tear
- Long service life with proper maintenance
Safety Features
- Mechanical
-
- Sturdy case to prevent breakage
- Fail-safe design for emergency situations
- Operational
-
- Smooth shifting to prevent drivetrain shock
- Overheat protection through cooling system
- Maintenance
-
- Easy access to service points
- Clear fluid level indicators
Comfort Features
- Noise Reduction
-
- Quiet operation at cruising speeds
- Insulated case design
- Shifting
-
- Smooth gear transitions
- Minimal lag between shifts
- Driving
-
- Consistent performance across speeds
- Reliable in various driving conditions
- Maintenance
-
- Easy fluid changes
- Accessible filter replacement
Accessories
- Upgrades
-
- Performance shift kits
- High-capacity transmission coolers
- Heavy-duty torque converters
- Tools
-
- Transmission jack
- Specialized seal puller
- Alignment tool for installation
- Fluids
-
- Dexron III transmission fluid
- High-temperature fluid additives
- Seal conditioners
Maintenance
- Service interval
- Every 30,000 miles or 24 months
- Service Items
-
- Fluid and filter change
- Inspect for leaks
- Check shift linkage
- Adjust bands
- Inspect torque converter
- Maintenance Notes
- Use only recommended fluids and follow torque specifications during reassembly.
Warranty
- Standard
- Miles: 50,000Years: 3Coverage: Parts and labor for manufacturing defects
- Extended
- Miles: 100,000Years: 5Coverage: Additional coverage for major components
- Rebuilt
- Miles: 30,000Years: 1Coverage: Limited to rebuilt parts and labor
- Warranty Terms
- Warranty void if improper fluids are used or if transmission is modified.
Production Details
- Manufacturer
- General Motors
- Manufacturing Process
-
- Precision casting for case
- Heat treatment of gears
- Automated assembly line
- Quality Control
- inspection: 100% inspection of critical componentsTesting: Dyno testing for performance verification
- Sustainability Practices
-
- Recycling of metal scraps
- Use of eco-friendly fluids
- Production Metrics
- Annual Output: 500,000 unitsDefect Rate: Less than 0.5%
Service Information for th400 transmission Service
Maintenance and service requirements specific to this component
- Change transmission fluid
- Replace transmission filter
- Inspect for leaks
- Check shift linkage
- Adjust bands
Ensure the vehicle is on a level surface during fluid changes.
- Inspect torque converter
- Check transmission mounts
- Test transmission cooler
- Inspect output shaft seal
Use a transmission jack for safe removal and installation.
- Rebuild transmission
- Replace clutch plates
- Inspect internal gears
- Test hydraulic system
Major services should be performed by a certified technician.
Common Questions
Find answers to common questions about torque specifications
Q1 Is the TH400 transmission compatible with other GM models from 1970-1991?
Is the TH400 transmission compatible with other GM models from 1970-1991?
The TH400 transmission is compatible with various GM models from 1970-1991, including Chevrolet, GMC, and Cadillac vehicles. It is designed for rear-wheel-drive setups and can handle high torque applications. However, compatibility depends on engine type, drivetrain configuration, and mounting points. Always verify specific vehicle requirements before installation.
Q2 What are the maintenance requirements for the TH400 transmission?
What are the maintenance requirements for the TH400 transmission?
The TH400 transmission requires regular maintenance to ensure longevity. This includes checking fluid levels every 3,000 miles, replacing the transmission fluid and filter every 30,000 miles, and inspecting seals and gaskets for leaks. Additionally, periodic adjustments to the shift linkage and band are recommended to maintain optimal performance.
Q3 How do I install or replace a TH400 transmission in a 1970-1991 GMC Jimmy?
How do I install or replace a TH400 transmission in a 1970-1991 GMC Jimmy?
To install or replace a TH400 transmission in a 1970-1991 GMC Jimmy, start by disconnecting the battery and removing the driveshaft, exhaust, and crossmember. Lower the transmission and detach it from the engine. Install the new unit by aligning it with the engine, securing the bellhousing bolts, and reattaching all components. Ensure proper fluid levels and test drive to confirm functionality.
Q4 What should I do if my TH400 transmission is slipping or not shifting properly?
What should I do if my TH400 transmission is slipping or not shifting properly?
If your TH400 transmission is slipping or not shifting properly, first check the fluid level and condition. Low or contaminated fluid can cause issues. Inspect the vacuum modulator, shift linkage, and bands for wear or misadjustment. If problems persist, internal components such as clutches or valves may require professional diagnosis and repair.
Q5 How can I optimize the performance of my TH400 transmission?
How can I optimize the performance of my TH400 transmission?
To optimize the performance of your TH400 transmission, upgrade to a high-performance torque converter, install a shift kit for quicker shifts, and use synthetic transmission fluid for better lubrication. Regularly inspect and adjust the bands and linkage. Ensure proper cooling with an auxiliary transmission cooler, especially under heavy loads or towing conditions.
Factory Service Resources
Access official service manuals, technical documents, and repair guides. These resources provide detailed procedures, specifications, and diagrams directly from the manufacturer.
1970-1991 GMC Jimmy TH400 Service Manual
Coming SoonThis manual provides detailed instructions for servicing and repairing the TH400 transmission in 1970-1991 GMC Jimmy models, including disassembly, reassembly, and troubleshooting.
TH400 Transmission Technical Service Bulletin
Coming SoonThis bulletin outlines common issues, updates, and fixes for the TH400 transmission as identified by GM, ensuring proper maintenance and repair practices.
TH400 Transmission Parts and Accessories Catalog
Coming SoonThis catalog lists all compatible parts and accessories for the TH400 transmission, including rebuild kits, torque converters, and performance upgrades.
Legal Disclaimer
Important information about using this content
Always refer to your vehicle's service manual and take appropriate safety precautions when performing any maintenance or repairs.
General Information
Warranty & Liability
The content on this website is provided "as is" without any representations or warranties, express or implied. We make no representations or warranties regarding the accuracy, completeness, or availability of the information.
We shall not be liable for any direct, indirect, special, or consequential damages arising from the use of information on this website.
Technical Information
- All specifications, including torque values, fluid capacities, and maintenance procedures, should be verified against your vehicle's factory service manual.
- Vehicle specifications and procedures may vary by model year, trim level, and region.
- Always follow the manufacturer's recommended procedures and safety precautions.
- Working on vehicles can be dangerous. Always take proper safety precautions and use appropriate safety equipment.
- If you're unsure about any procedure, consult a qualified professional mechanic.
Intellectual Property
About the Author
Expert automotive knowledge and experience
'/%3E%3Cpath d='M60 30a20 20 0 1 1 0 40 20 20 0 0 1 0-40zm0 45c16.5 0 30 7.5 30 16.8V100H30v-8.2c0-9.3 13.5-16.8 30-16.8z' fill='%23404040'/%3E%3C/svg%3E)
Diagnostic
Specialized in advanced diagnostic techniques using modern scan tools and oscilloscopes.
Repair
Expert in both traditional mechanical repairs and modern vehicle systems.
Additional Expertise
Documentation
Created over 500 detailed repair guides and technical documents.
Training
Conducted technical training sessions and contributed to repair databases.
Certifications & Research
Certifications
- ASE Master Technician Certification
- Advanced Diagnostic Specialist
- Hybrid/Electric Vehicle Systems
- Performance Tuning Expert
Research & Community
Actively researches emerging technologies and contributes to automotive forums.