Diagnosing the JR710E Torque Converter Clutch Failure
The Infiniti G37, powered by the high-revving VQ37VHR 3.7L V6, routes its 328 horsepower through the Jatco JR710E (RWD) or JR711E (AWD) 7-speed automatic transmission. While robust, the torque converter in these units is a known weak point as the vehicles age. As of 2026, many G37s are crossing the 120,000-mile threshold, bringing internal torque converter clutch (TCC) degradation to the forefront of enthusiast and independent shop repair bays.
Before tearing into the drivetrain, you must confirm the failure. A failing G37 torque converter typically presents with the following symptoms:
- Highway Shudder: A rhythmic vibration between 35-55 mph when the TCC attempts to apply partial lockup in 4th or 5th gear.
- Diagnostic Trouble Codes: P0744 (Torque Converter Clutch Circuit Intermittent) or P0746 (Pressure Control Solenoid 'A' Performance).
- Bearing Whine: A distinct whining noise that changes pitch with engine RPM, not vehicle speed, indicating a failing internal stator or turbine bearing.
- Delayed Engagement: A harsh 'clunk' or 2-3 second delay when shifting from Park to Drive, often caused by TCC debris contaminating the transmission valve body.
Essential Parts, Fluids, and Tooling
Sourcing the correct components is critical. The JR710E requires specific clearances and friction materials. Do not substitute the fluid with generic multi-vehicle ATFs, as the Jatco 7-speed relies on the precise friction modifiers of Nissan Matic S for TCC lockup stability.
| Component | Part Number / Specification | Notes |
|---|---|---|
| OEM Torque Converter | 31920-JK20C (Verify VIN) | Supersedes older JK20A/B revisions. Includes updated TCC lining. |
| Transmission Fluid | Nissan Matic S (or Idemitsu Type S) | Requires approx. 6-8 quarts for a TC swap and pan drop. |
| Flexplate to TC Bolts | Nissan 31362-JK20A (Qty: 4) | Torque-to-yield. MUST be replaced during reassembly. |
| Rear Main Seal | Nissan 22144-JA00A | Highly recommended while the engine block is exposed. |
| Exhaust Crush Gaskets | Nissan 20691-JK20A (Qty: 2) | For the Y-pipe to exhaust manifold connection. |
Vehicle Preparation and Drivetrain Teardown
Safety and proper support are paramount. The G37's front mid-ship engine layout means the transmission is tucked far back under the firewall. You will need a low-profile transmission jack, a standard floor jack, and a high-quality engine support bar.
Exhaust and Driveshaft Removal
Begin by removing the underbody aerodynamic shields. Disconnect the exhaust Y-pipe from the catalytic converters. The G37 exhaust hangers are notoriously stiff; use a pry bar and soapy water to slide the rubber isolators off the brackets. Next, mark the rear driveshaft relationship to the rear differential flange with a paint pen to maintain factory balance. Unbolt the four 14mm nuts securing the rear flex disc and the center support bearing, then slide the driveshaft out of the transmission tail housing. Plug the tail housing with a clean rag to prevent fluid leakage and debris ingress.
Starter and Wiring Disconnects
Remove the starter motor (two 17mm bolts) to expose the flexplate-to-torque converter access window. Rotate the engine clockwise using a 22mm socket on the crankshaft pulley to access all four torque converter mounting bolts. Disconnect the transmission main wiring harness connector on the passenger side of the JR710E case. Warning: The locking tab on this connector becomes brittle with heat cycling. Use a small pick to gently release the tab before pulling.
Transmission Separation and TC Extraction
Support the transmission pan with a padded jack. Remove the transmission crossmember (four 17mm chassis bolts, two 19mm mount bolts). Slowly lower the transmission jack while simultaneously lowering the engine support bar from above. This prevents the engine from tilting backward and tearing the throttle body coolant hoses.
Unbolt the bellhousing. There are several M12 and M10 bolts of varying lengths; map them out on a piece of cardboard to ensure correct reinstallation. Once all bellhousing bolts are removed, slide the transmission straight back. The torque converter should remain attached to the transmission input shaft. If it stays on the engine flexplate, stop immediately—the input shaft splines are damaged or the converter was not fully seated previously.
With the transmission on the bench, unbolt the torque converter from the flexplate and slide it off the input shaft. Inspect the transmission oil pump drive tangs for scoring. If the old TC failed catastrophically, you must drop the transmission pan and inspect the valve body for metallic clutch material before proceeding.
Critical Installation Steps and Seating Verification
Installing the new G37 torque converter requires precision. The converter must engage three distinct components: the oil pump drive gear, the stator support shaft, and the input shaft splines.
- Pre-Fill: Pour 1.5 to 2 quarts of fresh Nissan Matic S directly into the new torque converter hub. This prevents a dry start and immediate oil pump cavitation.
- Lubricate: Apply a thin film of assembly lube or petroleum jelly to the converter hub neck and the transmission front seal.
- Seat the Converter: Slide the TC onto the input shaft while simultaneously rotating it slightly. You will feel three distinct 'drops' or clicks as it passes the splines, stator, and finally seats into the oil pump gear.
- The Flush Test (CRITICAL): Lay a straight edge across the bellhousing mating surface. The torque converter mounting pads must sit at least 10mm to 15mm recessed behind the bellhousing surface. If the TC sits flush or protrudes, it is not fully seated. Forcing the transmission to the engine block in this state will instantly crack the aluminum transmission oil pump housing.
Torque Specifications and Reassembly
Reassembly is the reverse of removal, but adherence to factory torque specifications is non-negotiable to prevent drivetrain harmonics and case damage.
| Fastener Location | Thread Size | Torque Specification |
|---|---|---|
| Torque Converter to Flexplate | M10 x 1.25 | 35 ft-lbs (47 Nm) + Blue Threadlocker |
| Bellhousing to Engine Block (Large) | M12 x 1.25 | 36 ft-lbs (49 Nm) |
| Bellhousing to Engine Block (Small) | M10 x 1.25 | 22 ft-lbs (30 Nm) |
| Transmission Crossmember to Chassis | M12 | 65 ft-lbs (88 Nm) |
| Driveshaft Flex Disc to Transmission | M12 | 58 ft-lbs (78 Nm) |
| Exhaust Y-Pipe to Manifold | M10 Studs | 22 ft-lbs (30 Nm) |
Fluid Fill Procedure and TCC Relearn
The JR710E does not have a traditional dipstick. It utilizes an overflow plug located on the transmission pan. To fill the system correctly, the vehicle must be perfectly level. Pump in approximately 6 quarts of Matic S through the fill tube. Start the engine, cycle through all gears with your foot on the brake, and leave it in Park. With the transmission fluid temperature between 95°F and 113°F (35°C - 45°C), remove the overflow check plug. Allow fluid to drip until it slows to a slow, steady stream, then reinstall the plug with a new crush washer.
For a comprehensive look at advanced diagnostic procedures and community-tested workarounds for the JR710E valve body, the NICO Club G37 Forums remain an invaluable resource for real-world owner data. Furthermore, understanding the mechanical architecture of the Jatco 7-speed lineup helps explain why precise fluid pressures are vital for TCC longevity.
Performing the TCC Adaptation Relearn
Replacing the torque converter resets the physical friction boundaries, but the Transmission Control Module (TCM) still holds the adaptation values for the worn-out unit. If you do not perform a TCC relearn, the new clutch will apply with the wrong pressure, causing immediate shudder or slip.
Using a modern bidirectional scan tool (such as an Autel MaxiSYS or Topdon Phoenix), navigate to the TCM Special Functions. Select 'Clear Self Learning Data' followed by 'TCC Adaptation'. The tool will prompt you to drive the vehicle at specific speeds (usually 50 mph in 5th gear) while it monitors TCC slip RPM and adjusts the apply solenoid duty cycle in real-time. Once the slip RPM stabilizes below 20 RPM, the relearn is complete, and your G37 will shift smoothly for another 100,000 miles.
Expert Insight: If your old torque converter failed due to severe clutch material delamination, simply flushing the cooler lines is not enough. The JR710E valve body features microscopic solenoid screens that easily clog with TCC friction material. If you experience P0746 codes after the TC swap, the valve body must be removed and the solenoid screens cleaned or replaced to restore proper line pressure.
