What Is Hypoid Gearbox And Hypoid Gear Oil?

What is Hypoid Gearbox?

Hypoid gearboxes are a type of spiral bevel gearbox, with the difference that hypoid gears have axes that are non-intersecting and not parallel. In other words, the axes of hypoid gears are offset from one another. The basic geometry of the hypoid gear is hyperbolic, rather than having the conical geometry of a spiral bevel gear.

In a hypoid gear, the spiral angle of the pinion is larger than the spiral angle of the gear, so that the pinion diameter can be larger than that of a bevel gear pinion. This offers more contact area and better tooth strength, which means that more torque can be transmitted and high gear ratios (up to 200: 1) can be used. Because hypoid gear shafts do not intersect, bearings can be used on either side of the gear to provide additional rigidity.

The difference in spiral angles between the pinion and the crown (larger gear) causes some sliding along the teeth, but the sliding is smooth, both in the direction of the tooth profile and lengthways. This gives hypoid gears very smooth running properties and quiet operation. However, due to the pressure between the teeth, special EP (Extreme Pressure) gear oil is also required to maintain effective lubrication.

Hypoid gearboxes are a type of spiral bevel gearbox, with the difference that hypoid gears have axes that are non-intersecting and not parallel.
Hypoid gear

What is hypoid gear oil?

A hypoid gear oil is a lubricant that is designed to operate effectively with hypoid gear designs. Most gearboxes and differentials use hypoid gear designs and the lubricant must contain EP (extreme pressure) additives to prevent wear between the sliding surfaces of a hypoid gear mesh.

Hypoid gear oil sae 80W/90

GEAR OIL HYPOID SAE 80W/90 is a high-pressure gear oil that can be used wherever very high levels of stress occur, such as in cardan joints, hypoid gears etc. The first-class paraffinic base oils and the coordinated, innovative additives give the lubricating film an extremely high level of tear resistance, thereby preventing direct contact with metal.

Difference Between GL-4 and GL-5 gear oils

When deciding on a gearbox or gear oil, you may be wondering what GL-4 and GL-5 mean and what are the differences between these two classifications. Choosing the right classification is extremely important as both have different properties and incorrect use can cause serious damage to your vehicle.

There are four different classifications for transmission/gear oil. These different classifications define a certain level of performance in driven axles and manual gearboxes. They are mainly important for the transport sector in North America, Africa, and Asia. The active classifications are:

  • GL-1
  • GL-4
  • GL-5
  • MT-1

The higher the Extreme Pressure (EP), the higher the GL category is. It is important to know that the SAE Motor Oil Viscosity Chart (J300) is different from the SAE Gear Oil Chart (J306). The viscosity has no relation with the API Gear Oil Classification and should be chosen based on the recommendations from the manufacturer based on the temperatures where you will drive.

Is hypoid gear oil the same as GL5?

The main difference between GL-4 and GL-5 gear oils is the amount of EP additives. Sulfur/Phosphorus-containing products are used as EP-additive. This additive has the purpose to prevent the occurrence of micro-welds on the gear flanks at the local high temperatures which prevail in EP circumstances (temperatures well in excess of 800℃!) GL-5 has roughly twice the amount of EP additives compared to GL-4, which is why it is often used in high-pressure circumstances such as in a front axle and rear axle differential.

However, sulfur/phosphorus additives have an unfavorable property: they can react aggressively to bronze and copper. This can be catastrophic for the synchronizer rings of a transmission. Therefore, it is not recommended to use GL-5 in a gearbox unless the manufacturer allows it.

To conclude:

  • GL-4 is suitable for hypoid gear service when they are under severe service but are without shock loading.
  • GL-5 is suitable for hypoid gear service under severe service and shock loads and not for use in a gearbox.

Where are Hypoid Gearbox use?

Hypoid gears are generally used when the speed exceeds 1000 RPM (although ground gears above 8000 RPM are recommended). However, they are also useful for lower-speed applications that require extremely smooth running or quiet operation. In multi-stage gears, hypoid gears are often used for the output stage, where lower speeds and high torques are required.

The most common application for hypoid gears is in the automotive industry where they are used in rear axles, especially for large trucks. With a left spiral angle on the pinion and a right spiral angle on the crown, these applications have what is known as an “offset below center” which allows the driveshaft to be located deeper in the vehicle. This lowers the center of gravity of the vehicle and, in some cases, reduces the disruption of the interior of the vehicle.

Advantages of hypoid gearboxes

  • Use when installation space is limited
  • High torques
  • Quiet
  • Compact design
  • Can be combined with other types of gearbox
  • A hollow shaft is possible on the input shaft

Disadvantages of hypoid gearboxes

  • Complex design
  • Lower efficiency level than the planetary gearbox
  • Not suitable for fast speeds

FAQs.

What is Hypoid Gear?

A hypoid is a type of spiral bevel gear whose axis does not intersect with the axis of the meshing gear. The shape of a hypoid gear is a revolved hyperboloid (that is, the pitch surface of the hypoid gear is a hyperbolic surface), whereas the shape of a spiral bevel gear is normally conical.

What is Hypoid Gearbox?

Hypoid gearboxes are a type of spiral bevel gearbox, with the difference that hypoid gears have axes that are non-intersecting and not parallel. In other words, the axes of hypoid gears are offset from one another. The basic geometry of the hypoid gear is hyperbolic, rather than having the conical geometry of a spiral bevel gear.

What is hypoid gear oil?

A hypoid gear oil is a lubricant that is designed to operate effectively with hypoid gear designs. Most gearboxes and differentials use hypoid gear designs and the lubricant must contain EP (extreme pressure) additives to prevent wear between the sliding surfaces of a hypoid gear mesh.

Is hypoid gear oil the same as GL5?

The main difference between GL-4 and GL-5 gear oils is the number of EP additives. Sulfur/Phosphorus-containing products are used as EP-additive. This additive has the purpose to prevent the occurrence of micro-welds on the gear flanks at the local high temperatures which prevail in EP circumstances (temperatures well in excess of 800℃!) GL-5 has roughly twice the amount of EP additives compared to GL-4, which is why it is often used in high-pressure circumstances such as in a front axle and rear axle differential.

What are hypoid gears used for?

Hypoid gears are a type of spiral bevel gear that is used to transmit rotational power between two shafts at right angles. Their efficiency at transferring power is typically 95%, especially at high reductions and low speeds, while efficiency for worm gears varies between 40% and 85%.

What is hypoid transmission?

The hypoid gearboxes are a subcategory of spiral bevel gearbox with the axes of gears at an offset from one another. This helps in attaining an enhanced contact surface and a better tooth strength which allows for higher gear ratios and scope of higher torque transmission.

What is the advantage of hypoid gear?

The advantage of hypoid gearing is that the bevel pinion can be realized with a greater spiral angle because of the axis offset. This increases the overall coverage of the tooth. For this reason, hypoid gearboxes are capable of transmitting more torque than a single helical tooth.

What is the difference between hypoid and regular gear oil?

It’s a gearbox oil, just like others, but the ingredients are different. This type of gear oil is mixed with additives designed to increase its resistance to breakdown under high temperature and mechanical pressure produced by hypoid gearboxes.

Are hypoid gears Back drivable?

With efficiencies up to 95%, hypoid gears are not self-locking; it is possible for the transmission to back drive in the absence of holding torque or a brake.

How are hypoid gears made?

Most spiral bevel and hypoid gears are produced by either face-milling (single indexing) or face-hobbing (continuous indexing). To achieve a high level of geometric accuracy and surface finish, face-milled gears can be successfully ground. This finishing process has several advantages.

What is SAE 80W 90 hypoid gears?

Gear oil hypoid SAE 80W/90 is a high-pressure gear oil that can be used wherever very high levels of stress occur, such as in Cardan joints, hypoid gears, etc.

Why are special lubricants used with hypoid gears?

A hypoid gear oil is a lubricant that is designed to operate effectively with hypoid gear designs. Most gearboxes and differentials use hypoid gear designs and the lubricant must contain EP (extreme pressure) additives to prevent wear between the sliding surfaces of a hypoid gear mesh.

What is a hypoid differential that is used in most rear-wheel-drive vehicles?

Commonly found in axle differentials, hypoid gears are used to transmit power from the driveline to the axle shafts. They are basically spiral bevel gears, where the pinion engages below the centerline of the ring gear. This lowers the driveshaft away from the bottom of the vehicle.

What is the difference between spiral bevel and hypoid gear?

Like the straight bevel gear, a spiral bevel gear is approximately 96% efficient per stage. A hypoid gear is a type of spiral bevel gearbox, with the difference being that hypoid gears’ axes are in parallel planes but do not intersect. In other words, the axes of the hypoid gear are offset from one another.

Why is hypoid more suitable on commercial vehicles?

In most commercial vehicles, single-stage hypoid gears are used in the rear axles. Not only does this give a better fuel consumption: the noise level mostly is lower. Also, the number of rear axle parts is smaller, and hence the weight of a single ratio hypoid axle will be lower than of a two-stage hub reduction axle.

What is the difference between helical and spiral gear?

Spiral teeth operate the same as helical gears. They produce less vibration and noise when compared to straight teeth. The right hand of the spiral bevel is the outer half of the tooth, inclined to travel in the clockwise direction from the axial plane.

Where do the hypoid gears require special lubricant?

Hypoid gears require special lubricant because of the extreme pressure between the teeth. The sliding motion of the teeth is effective due to the use of special lubricants.

Why are helical gears quiet?

Helical Gears have teeth that are set on an angle to the gear axis. Since the teeth engage more gradually, they have a smoother and quieter operation than spur gears.

What are the disadvantages of helical gears?

Some of the disadvantages of helical gears are they are less efficient than spur gears due to tooth slippage. The diagonal profile of the teeth is what causes the slippage and also leads to axial thrust on the shaft. It is important to choose a bearing that can withstand the axial thrust generated by the gears.

What are the different types of helical gears?

Helical gears are available in two teeth configurations: left-handed and right-hand. Helical gears transmit energy through two axial configurations: parallel and perpendicular. In parallel-axis helical gears the two opposite-hand gears provide quiet operation and high load capacity.

Which is better spur or helical?

Helical gears are more durable than spur gears because the load gets distributed across more teeth. Hence, for a given load, the force will be spread out better than with a spur gear, resulting in less wear on individual teeth.

Are helical gears weaker?

While you may assume that straight cut gears are stronger because of the power and high performance they provide, they are actually considered to be much weaker than helical gears because helical gears hold more teeth which makes for a stronger load-bearing surface.