5spd Automatic Transmission
From Nissan 350Z & 370Z Wiki
What is it?
No more clutches to press. The advanced computer system senses the driver's demands via the accelerator, and responds accordingly. The driver may also choose to shift the gears using manual mode.
5AT
What are the gear ratios?
How much power will the transmission hold?
How do you change the oil?
How can I improve the Automatic?
What upgrades are available?
Do I need a transmission cooler?
Can I swap in the manual transmission?
Transmission replacement cost
Stall Speed
Stall speed is a term used to describe the rpm at which the torque converter transfers the power from the engine to the transmission. There are different ways to test stall speed. "Foot brake stall" is when you press the brake pedal and then press the gas pedal. When the car doesn't go anymore or the tires start to spin that is "brake stall". (DO NOT TRY THIS! THIS MEASUREMENT IS MEANINGLESS AND POTENTIALLY DANGEROUS TO YOU AND THE TORQUE CONVERTER!) "Flash stall" is when you, from a dead stop, press the gas pedal to wide open throttle (wot). Watch your tach needle, you will see the needle jump to a certain rpm, that is "flash stall". A drag racing-style trans brake will give you closer to the true stall speed of a torque converter.
What is torque multiplication?
Torque multiplication is a term used to describe the amount of torque the torque converter will multiply. A torque converter is basically a fluid coupling between your engine and transmission. There is no direct mechanical link until the torque converter is in lockup mode. The pump assembly of the torque converter is directly linked to the crankshaft of the engine, however the turbine assembly of the torque converter is not. It is connected to the transmission input shaft. When the oil is pumped to move the turbine it is actually pushing the turbine at a higher rate. Each torque converter pump and design pushes the fluid differently, therefore giving you different rates of turbine speed . All of this only means that different torque converters will give you different torque multiplication rates simply by design.
What does torque converter efficiency mean?
Once the torque converter does it's job multiplying torque for take off, the function of the torque converter is to be a link (sometimes called a fluid coupling)from the engine to the transmission. Keeping in mind that the pump assembly and the turbine assembly spin at different speeds, every torque converter has a different rate of slippage between the two. The amount of slippage is what determines efficiency. This is why auto manufacturers created lockup torque converters. Rather than having a torque converter that is let's say 92% efficient, they mechanically link the engine to the transmission, giving it a 1:1 ratio or creating 100% efficiency. This lowers the rpm of the engine, therefore increasing fuel efficiency.
Why do I need a higher stall speed converter?
Theoretically, for maximum acceleration the stall speed of the torque converter should match the peak torque rpm of the engine. A good explanation for the way it works is this: when you go outside jogging you start to breathe in and out faster and harder. Well the same thing goes for a performance engine. The engine is breathing in and out harder and faster, at a higher rpm. If a high performance engine makes power at a higher rpm, then a higher stall speed torque converter is what you need to put more power to the ground quicker.
Other upgrades when installing a new torque converter?
You might want to consider a performance tire upgrade such as a "drag radial" tire. Traction will be your biggest problem..... By putting power to the wheels, at a higher rpm, you begin to realize that a suspension upgrade might be a necessary upgrade as well. The only other recommendation is, depending on the application, some performance torque converters create more heat and long term heat kills transmission life. A light bulb that burns twice as bright burns half as long. ... Tests have shown that coolers can increase your cooling capacity by 100%. "
ABOUT DYNAMOMETER READINGS AND HIGH STALL TORQUE CONVERTERS
There is a misconception and a lot of misinformation about the poor vehicle performance numbers that are generated by testing a car with a high stall torque converter on a dynamometer. Most people that are not familiar with how a torque converter operates will automatically think that the torque converter is inefficient. This is totally false and the following facts are why you should not believe the dynamometer numbers while using an unlocked high stall torque converter. All late model dynamometers have a software program that commands the loading and speed of the vehicle over a certain period of time while making a test pull. The software used in these dynamometers is setup to be used with a locked 1:1 connection between the engine and the rear wheels, such as using a standard shift transmission in 3rd gear or when an automatic transmission has the torque converter clutch locked. When an unlocked high stall torque converter is used to make the pull and the dynamometer software has not been changed to allow for the fluid coupling differences the dynamometer readings will all be bogus. For instance, the low rpm torque readings will be high due to the torque multiplication of the torque converter being run in partial stall.
Likewise, the high rpm torque readings will be low due to the long period of time the dynamometer takes to allow the torque converter to transition from partial torque multiplication to a hydraulic locked condition. The only cure for this phenomenon is to rewrite the dynamometer software to prevent this from happening. Torque converters with a low STR or low stall are not as adversely affected by this phenomenon. The high rpm transition problems never occur when the vehicle is being driven or raced normally. Therefore, worrying about what the dynamometer numbers are is a total waste of time. If your dynamometer operator refuses to alter the software to give correct readings then the only things you can do is (1.) lock the torque converter clutch and do the testing, (2.) use the readings you get with an unlocked torque converter as a baseline and continue to tune the car like normal until you get the best numbers remembering these are just numbers and not the actual horsepower and torque or (3.) use a dynamometer shop that gives you the service you deserve for your hard earned money. The only really true test of the performance of a vehicle is to take it to the track and see what ET and MPH the car will run."
The Impeller
Also known as the pump or driving member; the impeller is driven by the engine. The many curved vanes force fluid outside the converter, creating centrifugal force when spun by the engine.
Stator
The reaction member is a smaller vained rotor located between and turbine. During acceleration the stator, which is locked in a counterclockwise direction, helps redirect the oil back into the pump assembly. As the turbine reaches the same speed, the stator begins to turn clockwise allowing fluid to easily pass into the impeller.
Turbine
Also known as the driven member, looks very similar to the impeller because of its shape and curved vanes. The outer blades of the turbine receive the force fluid of the impeller. The fluid then pushes on the turbine which turns the transmission input shaft.
Clutch and Damper Assembly
Only lock up units, this assembly is what mechanically links the turbine to the front cover. The clutch assembly, when activated by oil pressure, produces a one to one ratio between the motor and the transmission. this in turn lowers engine rpm's and increases fuel efficiency.
Front Cover
The front cover is what mechanically links the pump to the crankshaft of the motor. It also acts as the friction surface on lock up units.
Torque Converter Fact & Function
First, you need to understand the functions of a torque converter. One of the jobs of the converter is to act as a fluid coupling from the motor to the transmission. Another, and a very important function, is torque multiplication. What remains is stall speed, a very misunderstood term. Stall speed is directly related to the amount of torque your engine produces (the greater torque, the higher the stall speed). For example, a converter with a 2800 to 3200 rpm rating might provide approx. 3200 rpm of stall speed behind the big block making 500-plus lbs of torque and in a small block with less torque it's possible to only have a stall speed of 2800. Without knowing how much torque your engine produces, you cannot know how much stall speed a converter is capable of.
Factors That Affect A Converters Stall Speed
- Vehicle Weight
- Vane/Fin Angle
- Horsepower
- Impeller to Turbine Clearance
- Powerband/CamShaft
- Stator Design
- Torque Rate
- Converter Diameter
- Gear Ratio
SERVICE INFORMATION
If the automatic transmission in the new Q45 (F50) or G35 (V35) requires service, a new type of automatic transmission fluid MUST be used. The new fluid is Nissan Matic-J. The New Nissan Matic-J
- Only Nissan Matic-J automatic transmission fluid (P/N 999MP-MTJ00P) is specially formulated to meet the exacting requirements of Infiniti's new 5-speed automatic transmission (RE5R05A).
- The RE5R05A transmission contains new internal components that require the use of Nissan Matic-J only!
CAUTION:
- Usage of Nissan Matic-D or any other automatic transmission fluid in the RE5R05A 5-speed automatic
transmission will cause deterioration in driveability and transmission durability.
- Do NOT use any other fluid for the RE5R05A 5-speed automatic transmission, only use Nissan Matic-J.
- Use of any other fluid may result in damage to the RE5R05A 5-speed automatic transmission, which will not be covered by the INFINITI warranty......"
Drivetrain Definitions
Axle
- An axle is a central shaft for a rotating wheel or gear. In some cases the axle may be fixed in position with a bearing or bushing sitting inside the hole in the wheel or gear to allow the wheel or gear to rotate around the axle. In other cases the wheel or gear may be fixed to the axle, with bearings or bushings provided at the mounting points where the axle is supported.
Clutch
- A clutch is a subcomponent of an engine's transmission designed to allow engagement or disengagement of the engine to the gearbox or whatever apparatus is being driven.
- The coupling mechanism used on a mechanical power press to couple the flywheel to the crankshaft, either directly or through a gear train.
Differential
- A set of mechanical gears that eqaulises the power between the left and right drive wheels, particularly when cornering, when the outside wheel travels further than the inside wheel.
- A device - usually made of gears - that divides the torque between the driving wheels and permits the wheels to turn at different speeds. This is especially important when negotiating a corner, as the inside wheels turn more slowly than the outside wheels.
- A unit that takes the power of the rotating driveshaft at right angles to the rear axle and passes it to the axle. It will not only drive both rear axles at the same time, but will also allow them to turn at different speeds when negotiating turns. In this way the tires do not scuff or skid.
Driveshaft
- A driveshaft or driving shaft is a mechanical device for transferring power from the engine or motor to the point where useful work is applied. The 350Z incorporates a one-piece driveshaft which is actually carbon fiber reinforced plastic.
Final Drive
Flywheel
- A relatively large and heavy metal wheel that is attached to the back of the crankshaft to smooth out the firing impulses. It provides inertia to keep the crankshaft turning smoothly during the periods when no power is being applied. It also forms a base for the starter ring gear and, in manual transmission, for the clutch assembly. Also see engine flywheel and fluid flywheel.
- This is a large gear mounted to the back of the crankshaft which turns the engine when the starter is cranking.
- A flywheel is a heavy rotating disk used as a repository for angular momentum. Flywheels resist changes in their rotation speed, which helps steady the rotation of the shaft when an uneven torque is exerted on it by its power source such as a piston-based, (reciprocating) engine, or when the load placed on it is intermittent (such as a piston-based pump).
Gearbox
- A casing for gear sets that transmit power from one rotating shaft to another. A gear box has a number of functions: it is precisely bored to control gear and shaft alignment, it contains the gear oil, and it protects the gears and lubricant from water, dust, and other environmental contaminants. Gear boxes are used in a wide range of industrial, automotive, and home machinery.
- The shell (metal casing) in which a train of gears is sealed.
Gear Ratio
- The number of revolutions a driving (pinion) gear requires to turn a driven (ring) gear through one complete revolution. For a pair of gears, the ratio is found by dividing the number of teeth on the driven gear by the number of teeth on the driving pinion gear.
- A gearbox contains several toothed wheels that are connected and disconnected to each other in order to switch into the intended gear. The gear ratio is the ratio between the number of teeth of the two wheels that are connected at a given time. If one wheel has 25 teeth and the attached one has 50, there is a 2:1 ratio.
Limited Slip Differential
- A Limited Slip Differential (LSD) is a modified or derived type of differential gear arrangement that allows for some difference in rotational velocity of the output shafts, but does not allow the difference in speed to increase beyond a preset amount. In a car or automobile, such limited slip differentials are sometimes used in place of a standard differential, where they convey certain dynamic advantages, at the expense of greater complexity.
Pumpkin
- The rear pumpkin, or carrier, houses the final drive gears and differential.
Short Shifter
Toe
- Toe relates to the difference in the distance between the front of the tires and the rear of the tires on the same axle, or to the vehicle centerline. Toe-in, or positive toe, is defined as the front of the tires being closer together than the rear of the tires. Toe-out, or negative toe, is when the rear of the tires are closer together than the front of the tires. Zero toe is when the tires are parallel to each other.
- Effects of Toe: Excessive toe increases tire scuffing and results in tire wear and drag on the vehicle. Excessive toe-in, or positive toe, increases scuffing on the outside of the tire. Excessive toe-out, or negative toe, increases scuffing on the inside of the tire, and in some cases can cause a darting or wandering problem. Bias or bias-belted tires will commonly show a featheredge or saw-tooth toe wear pattern across the entire tire tread area. Any tire wear pattern caused by a toe condition can be further affected by an excess camber condition and may result in irregular wear patterns.
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This page is part of the Drivetrain category. To learn more about related items click the links below. Components: Clutches • Drivetrain Accessories • Final Drive Gear Sets • Flywheels • Limited Slip Differentials (LSD) • Short Shifters FAQs: 6spd Manual Transmission • Clutch (FAQ) • Drivetrain Definitions • Final Drive (FAQ) • Flywheel (FAQ) • Limited Slip Differential (FAQ) Tutorials: Automatic Shift Knob Swap • Automatic Shifter Removal • Automatic Transmission Fluid Replacement • Clutch Adjustment • Clutch Installation • Manual Transmission Fluid Replacement • Rear Differential Fluid Replacement • Shift Knob Removal and Replacement • Wheel Stud Replacement |
