The NSG370: A Comprehensive Guide to Aisin's Compact Manual Transmission
The NSG370 is a lightweight, compact 6-speed manual transmission that has earned its place as a reliable workhorse in Jeep applications. Whether you're a builder, shop owner, or enthusiast, this guide covers everything you need to know — specs, applications, common failure points, and where to find the best remanufactured NSG370 units available.
What Is the NSG370?
The NSG370 is a 6-speed manual transmission manufactured by Aisin Seiki, a Japanese automotive supplier known for precision engineering. It was used extensively in Jeep vehicles from 2005 through 2018, making it one of the most common manual transmissions in the Jeep ecosystem. The NSG370 was designed to handle moderate torque loads while maintaining smooth gear transitions and reasonable fuel economy — a solid choice for both daily drivers and trail rigs.
Key Specifications and Features
Gear Count: 6 forward speeds plus reverse, with a true overdrive 6th gear for highway efficiency.
Torque Capacity: Rated to handle approximately 180–220 lb-ft of torque depending on variant and application — well-matched to Jeep's 2.4L, 3.7L, 3.8L, 4.0L, and 3.6L Pentastar engines.
Weight: Lightweight construction at approximately 110–130 lbs, contributing to improved fuel economy and reduced unsprung weight.
Synchronizer Design: Helical gears with modern synchronizer technology for smooth, quiet shifts across the rev range.
Common Vehicle Applications
The NSG370 was used across a wide range of Jeep platforms:
- Jeep Wrangler TJ/JK (2005–2018) — 2.4L, 4.0L, 3.8L, and 3.6L Pentastar engines
- Jeep Liberty KJ (2005–2006) — 2.4L 4WD
- Jeep Liberty KJ (2005–2008) — 3.7L 4WD
If you're unsure whether your vehicle uses an NSG370, check the transmission identification tag on the case or consult your vehicle's service manual.
Tennessee Standard Transmissions NSG370 Units
When it comes to remanufactured NSG370 transmissions, Tennessee Standard Transmissions builds the best units on the market — and here's why:
- Complete remanufacture, not a rebuild: Every TST NSG370 is fully disassembled, cleaned, inspected, and rebuilt to OEM specifications — not just patched up and resold.
- All wear items replaced: Synchronizer rings, bearings, seals, gaskets, and thrust washers are replaced as a matter of course — not just the parts that look bad.
- Comprehensive warranty coverage: TST units are backed by a solid warranty covering defects in materials and workmanship, giving you real peace of mind.
- Core exchange program: Send us your core and reduce your overall cost — a straightforward process designed to save you money.
- Built by transmission specialists: TST focuses exclusively on manual transmissions. This isn't a side business — it's what we do.
Shop our remanufactured NSG370 units by application:
- Jeep Wrangler TJ/JK 2005–2018 (2.4, 4.0, 3.8, 3.6L) NSG370 6-Speed
- NSG370 2005–2006 Wrangler 4WD 4.0L Manual Transmission
- NSG370 2005–2006 Jeep Liberty 4WD 2.4L Manual Transmission
- NSG370 2005–2008 Jeep Liberty 4WD 3.7L Manual Transmission
- NSG370 2.4 / 3.6 / 3.8 / 4.0 Manual Transmission
Performance and Driving Characteristics
The NSG370 is praised for its direct, mechanical feel. The transmission provides solid feedback through the shifter and clutch — popular among Jeep enthusiasts who value engagement over modern convenience features. The 6-speed layout is well-suited for both trail use and highway cruising, with 6th gear providing a true overdrive that reduces engine RPM at sustained speeds.
The NSG370's synchronizers are robust and forgiving, making it relatively easy to shift smoothly even under load. Proper technique and maintenance are still essential for longevity.
Common Issues and Troubleshooting
Grinding on Downshifts: Worn synchronizers are the most common culprit. This indicates the transmission is nearing the end of its service life and should be rebuilt or replaced.
Difficulty Engaging Gears: Hard shifting can result from low or degraded transmission fluid, worn synchronizers, or linkage adjustment issues. Start by checking fluid level and condition.
Leaking Fluid: Seals and gaskets deteriorate over time. If you notice fluid under your vehicle, have the transmission inspected promptly to prevent further damage.
Clutch Chatter: While not a transmission issue per se, a chattering clutch often accompanies transmission problems. Ensure your clutch system is properly maintained and adjusted.
Maintenance Best Practices
Fluid Changes: Change transmission fluid every 30,000–60,000 miles depending on driving conditions. Use the correct fluid specification for your NSG370.
Clutch Care: Smooth, deliberate clutch engagement extends transmission life. Avoid riding the clutch and replace the clutch assembly if it shows signs of slipping or wear.
Linkage Adjustment: Proper shifter linkage adjustment ensures crisp, accurate gear selection. Loose or misaligned linkage causes grinding and premature synchronizer wear.
Inspection Schedule: Have your transmission inspected annually or whenever you notice changes in shifting feel, noise, or fluid condition.
Rebuild and Remanufacturing Considerations
When an NSG370 reaches the end of its service life, remanufacturing is a cost-effective alternative to sourcing a used unit. Key wear points include synchronizer rings (which glaze and wear with high mileage) and thrust bearings (which support axial loads). A quality remanufacture addresses all of these components and restores the transmission to like-new condition.
TST's rebuild and return service is also available — send us your unit and we'll remanufacture it to spec and ship it back. Learn more about our Rebuild & Return service.
NSG370 vs. Other Transmissions
The NSG370 occupies a solid middle ground in the manual transmission landscape — more robust than economy units but lighter and more compact than heavy-duty truck transmissions. For Jeep applications, it's a well-matched unit that handles the demands of both street and moderate trail use. If you're comparing options, a TST specialist can help you determine the best fit for your build.
Final Thoughts
The NSG370 remains a capable, reliable transmission that continues to serve Jeep builders and enthusiasts well. With proper maintenance and a quality remanufactured unit from Tennessee Standard Transmissions, these transmissions deliver years of dependable service — on the street and on the trail.
For more information, browse our full NSG370 transmission lineup or contact our team directly. We're here to support your build with expertise, quality products, and real warranty coverage.