Transmission-fluid advice for the Infiniti G37 is often oversimplified. The G37 was sold with different automatic and manual transmissions, and AWD models also use a transfer case and separate differentials. The correct fluid, fill procedure and service interval depend on the exact year, transmission and operating conditions.
Before buying fluid, identify the transmission from the VIN, owner’s manual and under-vehicle components. Do not assume that every G37 uses the same product or that a fluid marketed as universal meets the required specification.
Automatic, Manual and AWD Are Different
An automatic transmission uses fluid for hydraulic control, lubrication and heat management. A manual transmission uses gear oil or manual-transmission fluid with different friction characteristics. AWD adds transfer-case service, while the front and rear differentials use their own gear-oil specifications.
Servicing one component does not service the others. A shop invoice that says drivetrain fluid should identify exactly which unit was drained and what fluid was installed.
What Infiniti’s Maintenance Guides Say
Infiniti’s maintenance guides instruct owners to inspect transmission fluid or oil for leaks at specified intervals. Earlier G37 maintenance information also calls for replacement under certain severe-use conditions, such as towing, using a car-top carrier or driving on rough or muddy roads. One 2011 guide lists a 30,000-mile or 24-month replacement interval for those conditions, except for vehicles with the seven-speed automatic transmission.
That exception is important. It shows why one interval should not be applied to every G37. Use the maintenance guide for the exact model year and transmission, and consider how the car is actually used.
When a Fluid Change Makes Sense
Fluid service is reasonable when it is required by the schedule, the fluid history is known, a leak repair has opened the system or the vehicle has experienced severe use. Preventive service is most effective before the transmission develops serious mechanical symptoms.
A drain-and-fill replaces only part of the automatic-transmission fluid because fluid remains in the torque converter and internal passages. Repeating a drain-and-fill after appropriate operation may exchange more fluid gradually, but the plan should follow the service information.
Drain-and-Fill Versus Machine Exchange
A drain-and-fill is a controlled service that removes the amount available through the drain and refills it to the correct level. A machine exchange replaces a larger portion of the fluid by circulating new fluid through the system. Neither method should be described as universally good or universally harmful.
The appropriate method depends on the transmission’s condition, fluid history, available service equipment and manufacturer procedure. A machine should never use cleaning chemicals or pressure outside the approved process. When the history is unknown and the transmission already slips or shudders, diagnosis should come before any exchange.
Fluid Specification Matters
Use the exact Infiniti or Nissan fluid specification listed for the transmission. Friction characteristics affect shift timing, clutch engagement and temperature. A fluid that has the correct viscosity but the wrong additive package may create poor shift quality.
Manual-transmission and differential fluids also require the proper viscosity and performance rating. Never install automatic-transmission fluid in a component simply because it is red, and never judge fluid only by color.
Checking and Setting the Fluid Level
Some G37 transmissions do not use a simple owner-accessible dipstick. Fluid level may need to be checked through a fill or overflow plug at a specified fluid temperature while the vehicle is level. This requires safe lifting, a scan tool or temperature measurement and the correct sequence for moving the shifter through its positions.
Overfilling can aerate fluid and cause poor operation. Underfilling can reduce lubrication and hydraulic pressure. If the proper temperature-based procedure cannot be followed, professional service is the safer choice.
Symptoms That Need Diagnosis First
Delayed engagement, slipping, flare between shifts, severe shuddering, a burning smell, metal debris or a transmission warning should be diagnosed before routine service. Fluid cannot repair worn clutches, damaged bearings, valve-body faults or electrical control problems.
A scan of the transmission-control module and a road test can provide valuable information. Ask the shop to document codes, fluid condition and any debris found in the pan or drain fluid.
Manual-Transmission Service
The six-speed manual transmission also benefits from correct fluid and periodic leak inspection. Difficult shifting can be caused by old or incorrect fluid, but clutch hydraulics, clutch wear, synchronizers, mounts and shifter components must also be considered.
Use only the specification approved for the manual gearbox. Some popular aftermarket fluids change shift feel, especially when cold, but owner preference is not a substitute for compatibility.
AWD Transfer Case and Differentials
AWD G37 owners should include the transfer case and both differentials in the maintenance plan. Inspect axle seals, pinion areas and case seams for leaks. Fluid that is low because of a leak should not simply be topped off repeatedly.
Tires are part of AWD maintenance. Closely matched size and tread depth reduce speed differences between axles and help protect the transfer case.
What to Ask a Repair Shop
Ask which transmission is in the vehicle, which fluid specification will be used, whether the service is a drain-and-fill or exchange, how the final level will be set and whether the pan or filter is being removed. Request the old-fluid condition and any debris findings on the invoice.
A professional shop should also explain whether the vehicle’s symptoms suggest maintenance or a mechanical diagnosis. Avoid shops that promise a fluid change will cure every shift problem.
Final Thoughts
The best G37 transmission service is model-specific, properly documented and performed before major symptoms develop. Identify the transmission, use the correct fluid, set the level at the specified conditions and treat the transfer case and differentials as separate components. When the transmission already behaves abnormally, diagnose first and service second.
Primary references checked: INFINITI manuals and guides | INFINITI recall lookup | NHTSA recalls and service documents