The primary function of a limited slip differential (LSD) is to effectively distribute torque as needed. During regular driving conditions, a positraction LSD is engaged, ensuring equal traction is provided to both wheels. However, when the throttle is aggressively pressed, tight corners are taken, or when navigating through loose gravel trails, the LSD kicks in to limit wheel spin across the drive axle. It achieves this by allowing the axle shafts to spin at different speeds while continuously attempting to balance the distribution of torque between the two axles. Consequently, power is transferred to the wheel that has the best traction, thereby improving grip, control, and overall predictability of the vehicle.

Learn more about limited slip differentials in our How It Works blog article here.

Watch our “Are Posis Worth It?” video to get more info about limited-slip differentials.

Are Posis Worth It?

When traveling in a straight line where wheel speeds are identical on both sides, all LSDs continuously provide equal traction to both tires. The difference between LSD types has to do with how this occurs and what happens when additional traction is needed.

In a clutch-type unit, the spring array applies pressure to the side gears which puts pressure on the clutch packs in the outer part of the carrier. Both axles get equal pressure and both tires get equal traction. When a tire starts slipping, the clutch packs are engaged with different resistance. The clutches work to maintain synchronization between the tires, transferring more torque to the tire that has the best grip while reducing torque transfer to the tire that has less grip.

A gear-type LSD has no frictional surfaces to initiate torque transfer. It uses floating helical-cut worm gears that operate in pockets and mesh together. Under normal driving conditions this type of LSD acts like an open diff. When acceleration or wheel slippage occurs, axial and radial thrust is applied to the helical gear pinions in their pockets. Under these loads, more torque is transferred to the tire with the best traction in a progressive manner as torque is withheld from the tire that is slipping.

Yes. Your ride will drive better than ever because both wheels will receive traction. When things get hot the Spartan Helical LSD will limit wheelspin across the drive axle by permitting the axle shafts to spin at different speeds while continuously trying to balance the application of torque between the two axles. This results in transferring more power to the wheel with the best traction. This improves vehicle control and performance. Mashing the throttle, taking a tight corner aggressively, or working through loose gravel or challenging sections of trail will actuate the unit’s gear array to increase your traction.

Get for more information on the Spartan Helical LSD and LSDs in general in our Stengths & Advantages Of The Spartan Helical LSD blog article.

Some are, some aren’t.

Clutch-type LSDs, like our Dura Grip, can be rebuilt. Rebuilding involves replacing the clutches in the unit. The clutches can be replaced to bring the unit back to its original performance level, or non-stock clutches with different friction characteristics and springs with custom compression rates can be used to fine tune the Dura Grip’s performance to better match the style of driving/racing you are doing.

Gear-type LSDs, like our Spartan Helical, do not require rebuilding because there are no clutches to replace, there is nothing to rebuild. The unit’s internal worm gears should last the life of your vehicle.

Using non-synthetic 80W-90 GL-5 will produce optimum performance in our Dura Grip clutch-type units.

Learn more about LSD oils, and drivetrain lubrication in general, by watching our “Tech Talks, Oils and Additives” video.

Tech Talks, Oils and Additives

The "GL-5" designation identifies how much Sulphur-based friction modifier is present in the oil. This chemical modifier helps the oil function under extreme pressure… like in an LSD. Note: Because of its Sulfur content GL-5 oil is meant to be used on hypoid gears in differentials only; it is too corrosive to be used in transmissions, which require a milder GL-4 formulation.

First, this product is for clutch-type differentials only, not gear-driven limited slips like our Spartan Helical LSD. Friction modifiers are all about chatter. They guard against abnormal clutch engagement and/or disengagement (source of the chatter), ensuring the proper friction characteristics between clutch discs are maintained.

Yes. Yukon Friction Modifier Additive is our own proprietary formula designed specifically for the composite clutches in Yukon LSDs. If you run a Dura Grip, do not use parts store grade modifiers because they are formulated for OEM paper-style clutches. They are watered-down formulas, containing one-fifth the abrasive chemicals.

Yes. There is an order to the madness. There is a prerequisite method involved where have one parameter dialed in leads to the next step.

1. Pinion Depth

2. Pinion-Bearing Preload

3. Backlash

4. Carrier-Bearing Preload

Start by making wide, sweeping changes and whittle the adjustment down by making smaller and smaller changes. In this context consider 0.005” to 0.015” as a ‘large’ adjustment and 0.002” to 0.004” as a ‘small’ change.

For more indepth information check out our 12 Tips For Differential Assembly And Setup blog article.

On a crush sleeve design differential it usually takes between 300 and 400 ft-lbs of torque to crush the crush sleeve. Over the years we have used huge breaker bars and/or very strong air operated impact wrenches to crush the crush sleeve.

For more indepth information check out our 12 Tips For Differential Assembly And Setup blog article.

Lockers produce 100% lock-up where all the power is directed to both tires all the time when the unit is engaged. Lockers are tougher. Limited slips direct torque to both tires and when slippage occurs the unit directs torque to the tire with the best traction. LSDs do not generate 100% lock-up. Limited-slip diffs do not require activation from the driver. Their engagement is mechanical, a reaction to driving conditions, namely load and wheel slippage.

Learn more about the features and benefits of different Yukon and USA Standard Gear traction devices by checking out our “Which Traction Device is Right for You?” video.

Which Traction Device is Right for You?

Size, as it relates to strength and ease of installation. The smaller Spartan Locker, also known as a lunchbox locker or an insert-type unit, is easier to install because it replaces the spider gears. Since the Spartan Locker is installed in the carrier it relies on said carrier for strength. The Grizzly Locker, sometimes called a mechanical locker or automatic locker, is bigger and significantly stronger. It replaces the entire carrier assembly and has more clamping force, forged internals, and a forged 8620 low-nickel alloy steel case that is much more robust than the OE carrier it replaces.

Gain more insight into lockers by checking out our “Installing a Spartan Locker,” “Unboxing a Spartan Locker,” and “Yukon Grizzly Locker” videos.

Installing a Spartan Locker

Unboxing a Spartan Locker

Yukon Grizzly Locker

An advantage of an air locker like our Yukon Zip Locker is immediate engagement. A con is the need to purchase and plumb an air system in order to engage the locker. Other types of lockers take a moment to engage, half a tire rotation or so, which doesn’t sound like much until your rig is teetering between upright and rollover.

To better understand air lockers, check out our “How to install a Yukon Zip Locker” video.

How to install a Yukon Zip Locker

The pattern refers to how the ring gear and pinion gears mesh. There is a process used when reassembling a differential that optimizes ring gear and pinion tooth contact. The procedure involves changing the pinion position via shims in the carrier and repositioning the carrier. Dialing in the tolerance between the gears will ensure a smooth-running, long-lasting differential.

For more info on reading gear tooth patterns, check out this video from our Resource Center.

Reading Gear Teeth

It’s all about math… and counting teeth. Simply count the teeth on the ring gear and divide that number by the number of teeth on the pinion gear. Be aware that you may have to round off the number. (45 divided by 12 = 3.75… rounded to 3.73). The ratio itself refers to how many times the pinion gear rotates to turn the ring gear one full rotation.

Gearheads have their own vernacular so knowing the lingo will help you communicate with your mechanic. We’re talking about gear ratio. Tall gears produce a lower numeric ratio i.e. 3.08, 3.73 (or lower), while short gears or deep gears refer to higher numeric ratios i.e. 4.88, 5.29 (or higher).

Numerically higher gear ratios produce more torque, are quicker off the line, and deliver a lower top speed. Conversely, lower numeric gear ratios produce less torque, are slower at launch, and deliver a higher top speed. For more on how to pick the right ratio, check out this video.

Variables to consider include tire size (especially if it’s changing), transmission ratio, rpm at cruising speed, the stock gear ratio, and the intended usage of the vehicle. The tradeoff here is off-the-line acceleration versus freeway-speed performance.

Re-gearing serves two purposes. It can re-gain lost drivability in daily driven vehicles that have bigger tires installed or custom tailor performance for a dedicated off-roader that doesn’t put as much emphasis on daily driving.

If you’re adding big tires, technically you’re already re-gearing your ride because the increase in tire circumference changes the final drive ratio. Think about it this way… if you’re running a 3.73 gear, the pinion gear rotates 3.73 times to turn the ring gear one full rotation. On the road a bigger tire will take more rotations to get up to speed (slower) but require a lower engine rpm to maintain a highway speed. In some cases, bigger tires can create profoundly adverse driving characteristics and a reduction in fuel efficiency.

To figure out what your rig is doing and how to pick the right ratio you need to know your gear ratio and tire height in stock trim. These factors can be used to determine your engine rpm at a given vehicle speed. Our homepage has easy-to-use calculators that compute gear ratio and tire height. Then you take those numbers and feed them into our RPM calculator.

Use your stock set-up as a baseline to see what your stock vehicle speed to engine speed relationship is. If your rig is a daily driver you’ll want to gauge performance at freeway speeds. If you’re dialing in a dedicated off-roader, freeway speed performance will be less critical so you may want to evaluate slower vehicle speeds. Once your baseline is established, enter your new tire diameter and adjust the gear ratio to best match the stock numbers for daily drivers or the desired performance of a dedicated off-roader.

Check out our calculators here.

The term “thick gears” refers to a ring gear that is thicker than stock to maintain proper meshing in a carrier that is being upgraded with a numerically higher gear ratio. When increasing gear ratio, a smaller diameter pinion gear is employed and the thicker ring gear makes up the difference by moving the gear teeth ‘higher’ so the two gears mesh properly.

Get more info on Yukon ring and pinion gears by watching our “Unboxing Yukon Ring and Pinions” video.

Unboxing Yukon Ring and Pinions

We do all the thinking. Each kit contains all the parts needed to complete the job from start to finish so you know you’re getting all the right stuff the first time. The kits include a ring and pinion and all the bearings, seals, and small parts in one simple part number. Some kits are configured to address one axle, some cover both, and some include a Dura Grip limited-slip differential. A Yukon Pro Kit features a premium Yukon Gear & Axle gear set and uprated hardware to meet the demands of wheeling, off-road racing, track racing, street driving, and performance diesel. USA Quick Kits are affordable, general repair options when stock performance and reliability are the prime concerns.

Pinion bearing preload is related to the amount of force the pinion nut exerts on the pinion and its bearings. Axle builders generally measure the pinion’s preload by rotating the pinion gear by its nut with a pound/inch-graduated torque wrench. Crush sleeves or shims are generally used to set pinion preload. The proper torque ratings for new bearings can be found in the front of the installation manual on the Set Up Specifications page or by way of the chart below. Note: Measurements are for the use of new (not used) bearings.

It’s the point where the numeric increase in gear ratio necessitates a new/different carrier be used. The act of increasing the numerical ratio of a gear set results in the diameter of the pinion gear becoming smaller. To maintain proper contact, the thickness of the ring gear can be increased. The point at which thickening is no longer viable is known as the Carrier Break, which necessitates the move to a larger carrier with a taller deck height.

To see the Carrier Break points of popular differentials, check out this article from our Resource Center.

Carrier Break Points

It is the measurement from the base of the housing to the gear teeth. This mounting surface within the housing changes to accommodate the smaller pinion gears that are used when swapping to numerically higher gear ratios. A taller deck height maintains proper contact between the ring and pinion gear teeth by moving the ring gear farther ‘up’ in the housing.

All new gear sets require a break-in period to prevent damage from overheating. After driving the first 15 or 20 miles it is best to let the differential cool before proceeding. We recommend at least 500 miles before towing. We also recommend towing for very short distances (less than 15 miles) and letting the differential cool before continuing during the first 45 towing miles. This may seem unnecessary but we have seen many differentials damaged from being loaded before the gear set was broken in.
Changing the gear oil after the first 500 miles is also recommend. This will remove any metal particles or phosphorus coating that has come from the new gear set.

Get more info in these blog articles Proper Break In Process – Keeping Gears Cool During Break-In –  12 Tech Tips For Proper Differential Assembly & Setup

Spider gears are also known as satellite gears, they rotate around the side gears in the differential carrier. Side gears may also be referred to as axle gears or planetary gears. The spider gears are the ones with the cross-pin shaft going through them. This array of spider and side gears take the rotational energy from the driveshaft and help redirect it outwards to the axles and on to the wheels. They also play a key role in allowing the wheels to rotate at different speeds when the vehicle is turning.

For a more in-depth look, view this installation video from our Resource Center.

Spider Gears Video

Whirring noise only while decelerating at any or all speeds is most likely caused by bad pinion bearings or loose pinion bearing preload, and almost never by bad ring and pinion gears.

A howl or whine during acceleration over a small or large speed range is usually caused by worn ring and pinion gears or improper gear set up.

Rumbling or whirring at speeds over about 20 mph can be caused by worn carrier bearings. The noise may change while turning.

Regular clunking every few feet may indicate broken ring or pinion gears.

Banging or clunking only on corners can be caused by broken spider gears, lack of sufficient positraction lubrication, or worn positraction clutches.

Rumble while turning may indicate bad wheel bearings.

A steady vibration that increases with the vehicle’s speed can be caused by worn u-joints or an out of balance driveshaft.

Clunking only when starting to move or getting on and off the gas might be loose yokes, bad u-joints or worn transfer case or transmission parts.

Performance driveshafts, like those from Yukon Gear & Axle are engineered for extreme conditions. They use premium materials at every juncture, double cardan joints, high-strength steel, and superior manufacturing techniques to handle the increased articulation to accommodate lifts, reduce vibration, and improve durability on the trail, the track, or the open road.

See what makes Yukon driveshafts special by watching our “Yukon Performance Driveshafts | Engineered for Ultimate Performance” video.

Yukon Performance Driveshafts | Engineered for Ultimate Performance

Replacement driveshafts are direct-fit units built to or beyond OE specifications. Quality replacement driveshafts also address OE issues like under-sized u-joints that are often the cause of wear and/or imbalance. Upgraded aftermarket replacements, like those from USA Standard Gear, have gone through in-depth testing and have eliminated any vulnerable parts to produce a driveshaft that will last as long as you own your vehicle.

Learn more about USA Standard Gear replacement driveshafts by checking out our “Installing a USA Standard Gear Driveshaft” video.

Installing a USA Standard Driveshaft

Depends on the axle type. Semi-float and C-clip-equipped axle shafts are measured from the end of the shaft to the outer edge of the mounting flange. Axles with yokes (front axle shafts) are measured from the center of the u-joint bore to the end of the splines. Full-float designs are measured from the spline ends to the front surface of the mounting flange.

Click here for a detailed schematic of how to properly measure axles.

These kits are for shops and builders who have shims on-hand and are looking to save money over a Master Overhaul Kit. They include carrier bearings and races, pinion bearings and races, a pinion seal, marking compound, and a brush.

A semi-float axle rides on an outer bearing, thus supporting the weight of the vehicle. In semi-float applications the wheel is bolted directly to the axle. A full-float axle is a housing type in which the axle does not carry the load of the vehicle and does not have the wheel bolt directly to it. Full-float axles bolt to a spindle, which ultimately drives the wheels. They can also be removed with the wheel still on the vehicle.

Get some great insider information from our “How to Identify Your Differential & Axle Type | Differential Tech Tips” video.

How to Identify Your Differential & Axle Type | Differential Tech Tips

Yukon Gear & Axle Spin Free Kits replace the failure prone and expensive factory unit bearings with tapered bearings and races. The result is not only a design which is easier and more economical to service, but one that offers significant increases in fuel efficiency because there are fewer rotating parts in the drivetrain for the engine to turn. Less work equals better fuel economy.

Check out our “Yukon Spin Free Kit Installation Walkthrough” video to learn more about these highly effective kits.

Yukon Spin Free Kit Installation Walkthrough

A cold roll formed axle shaft is subjected to a great deal of pressure via cam-like tooling dies in the mill machine that imprint the shaft with splines. The intense pressure re-arranges the grain structure of the metal which ensures consistent hardness throughout the spline teeth and shaft unlike a cut-spline technique where material is removed from the shaft to create the splines. Yukon seals the deal with its induction hardening process where the axle is heated with an induction coil to around 1,600-degrees Fahrenheit then quenched, ensuring the proper heat penetration is achieved. Again, grain alignment within the metal and enhanced strength is the big benefit. Ultimately, the attention to detail that Yukon brings to the table results in an axle that is primed to absorb tons of trail abuse and provide years of dependable service.

The goal is to alter the properties of the metal on a molecular level, producing a tighter grain structure that changes the hardness, strength, toughness, ductility, and elasticity of the material in a beneficial way.

Induction hardening is the method Yukon uses on its entire line of performance axles. The process starts with an axle shaft that has likely been fully machined with splines etc. The shaft is heated with an induction coil to a predetermined temperature usually between 1,550- and 1,600-degrees Fahrenheit then quenched. Quenching is basically dousing the part with water or dropping it in an oil bath to quickly cool it. Yukon’s quality assurance staff will test axles from random production batches to ensure they receive proper heat treating and measure up dimensionally to engineering blueprints.

Universal Joints: Using a grease gun, pump grease into the universal joint until fresh grease can be seen coming out of all four seals. If all four seals do not purge fresh grease, move the driveline to free up the bearings caps and try again until successful.

Slip Yoke & Stub Shaft Assemblies: Coat both the slip yoke and stub shaft thoroughly prior to assembly, and then fully collapse the driveline. Apply grease via the grease fitting until grease begins to come out of the welch plug vent hole. After grease appears in the vent hole, cover it and continue to grease until it begins to show grease in the seal. During re-lubrication it may not be possible to fully collapse the driveshaft. Use the same greasing guidelines as used during initial assembly but be careful not to overfill the driveshaft. Overfilling the driveshaft with grease may cause the welch plug to pop out during use.

Centering Kits: Using a needle nose grease gun, pump grease into the flush mount zerk fitting on the centering kits until fresh grease appears at the ball seal or purge hole. Failure to maintain grease in centering kits can cause failure very rapidly. Worn centering kits will squeak, indicating that greasing is necessary immediately.

How often a driveshaft should be lubricated is determined by how the vehicle is used. We recommend the following lubrication guidelines:

Vehicle Usage     Lubrication Schedule    Approximate Mileage
City                      Bi-monthly                          6,500
Highway               Monthly                             12,000
Off Highway      Every 3 months                     6,500
Off Road               Monthly                             2,500

The ID tag location varies by manufacturer.

New Venture – Round tag on the back of the unit.

Borg Warner – Tin tag located on the case half bolts.

Magna – Sticker that can be found in a few different locations on unit.

Transfer cases use a combination of Drive, Housing, and Shift Types.

Drive types:

Gear driven transfer cases use a set of gears to send power to the front and rear axle. While gear driven transfer cases are more durable, they are also louder and less practical for smaller vehicles because of their weight.

Chain driven transfer cases use a chain in place of a gear set. Though most chain driven cases only drive one axle, there are case systems designed to drive both axles with a chain. Chains are lighter and quieter, but weaker than gear sets.

Housing types:

Married transfer case housings are bolted to the transmission, often between the output shaft and the main driveshaft. Some married transfer cases share their housing with the transmission.

Independent housings are installed separately from the transmission casing and are connected to the transmission output shaft with another driveshaft.

Shift types:

Manual Shift On-the-Fly (MSOF) transfer cases are controlled with a lever on the driver’s side floor of most vehicles. These transfer cases have two automatic sealed front axle hubs or two manual front axle hub selectors. High 4WD settings can be engaged at low speeds, but low 4WD settings must be engaged when the vehicle is stationary and the transmission is in neutral.

Electronic Shift On-the-Fly (ESOF) transfer cases have a dash-mounted selector, usually a switch or set of buttons. These cases have sealed automatic locking front axle hubs and a transfer case motor. High and low 4WD is engaged in the same ways as a MSOF transfer case.

First, let’s consider a rebuilt transmission. In most cases, a vehicle experiencing transmission problems is brought to an automotive repair shop. There, the transmission is removed and worked on by a mechanic who completely disassembles the transmission all the way down to its component nuts and bolts.

The mechanic inspects and cleans each and every transmission component and determines which parts are in working order, excessively worn, or just plain damaged beyond repair. Parts deemed worn or damaged are replaced with new or “used” components, and the unit is then reassembled. Once completed, the transmission is reinstalled and the vehicle is ready to hit the road. In this scenario, the transmission has been “rebuilt” – repairs have been made, bad parts have been replaced, but the unit has received few, if any, upgraded components.

A remanufactured transmission is basically the same as a rebuilt transmission, but the work has been performed by a dedicated transmission repair facility or shipped to the original transmission manufacturing facility. By opting for a transmission remanufacture, the customer is assured the transmission is being repaired by absolute experts on that particular transmission and has been remanufactured to incorporate all design and component upgrades that weren’t available when it was originally manufactured. This example also applies to transfer cases and differentials.

High stress driving will repeatedly increase the temperature of your transmission, eventually breaking down the stability of the gear oil in your car. If you regularly tow, drive in low traction conditions, or drive in mountainous regions, you will likely need to change your gear oil every 30,000 miles, or potentially even less.

In normal driving conditions, most cars can travel up to 80,000 miles before needing a gear oil change. However, this number is a maximum, and most manufacturers recommend changing your gear oil between 50,000 and 60,000 miles.

Other conditions that require a gear oil change can develop under unusual circumstances. For example, if your transfer case, differential component, or transmission has experienced submersion in water or another foreign fluid, your gear oil should be replaced. Contaminated oil can seriously damage your gearbox, transfer case, or differentials with inadequate lubrication.

You should also replace your gear oil if your transfer case or differentials recently had a leak repaired. A leak could signal contamination or low levels of gear oil. Most mechanics will replace your gear oil after repairing a leaky component, but this is sometimes forgotten during home repairs.

Lastly, if you or your mechanic finds dirty gear oil during a checkup, it should always be replaced. Old or dirty oil leads to destabilized viscosity and poor lubrication, which will prematurely damage your gearbox, transfer case, and/or differentials.

We predominantly use five metal types; 4320, 4340, 8620, 9310, and 1541H.

4300-series is a nickel-chromium-molybdenum alloy, i.e. chromoly, that’s low in carbon content. 4320 is used for the internals in our line of Yukon Dura Grip LSDs. We use 4340 in the manufacturing of forged gears, pinion gears, high-performance axles, Super Joints, and more. 8620 is a low-nickel alloy steel generally used in the manufacture of forged camshafts, crankshafts, and fasteners. We use it in gears and cases. 9310 is an alloy steel with more nickel and chromium than 8620. 9310 can better endure high shock loads without failing and we use it in Spartan Lockers. 1541H is a high-grade carbon steel used in our replacement axles and u-joints, and similar products. A caveat here, heat-treating plays a definitive role in a given alloy’s hardness and other properties that impact their performance in automotive drivetrain applications. We use advanced heat-treating techniques to fine tune our alloys to their intended usage.

Tensile Strength refers to the amount a material can be pulled/stretched before it fails (breaks). Torsional Strength: The amount a material can be twisted before it fails (ruptures). Both can be pertinent in the evaluation of materials used in drivetrain parts.

DOM, which stands for Drawn Over Mandrel, is a tube milling technique where coils of steel are formed into strips of a predetermined width. The strip is electric resistance welded and cold drawn into tubing, often called a hollow. The DOM process consists of pulling the tube/hollow through a die, inserting a carbide mandrel inside the tube, running it through the die again. The mandrel draw is repeated until the tube attains its final/desired specs. The pressure of the cold-drawing produces tubing with superior tensile strength, uniform wall thickness, highly precise inner and outer diameter tolerances, and the highest possible weld strength. This production technique is popular in the manufacture of axle tubes, driveshafts, roll cages, shock absorber bodies, and other automotive and inustrial applications.

Nodular cast iron, like we use in the manufacture of Yukon Hardcore Diff Covers, features graphite particles that present as spherical nodules. These nodules give this type of cast iron more strength and flexibility because they interrupt the matrix less than regular gray cast iron, whose graphite particles take the shape of flakes within the grain of the metal’s microstructure. Learn more about Yukon Hardcore Diff Covers here.

Stretching. A tow strap is designed not to stretch, which makes towing a vehicle at a constant speed easier. A recovery strap is designed to stretch so the rescue vehicle can get a little momentum before the strap goes taut and pulls the stuck vehicle free.

Yukon offers warranties against manufacturing defects for terms from one to 10 years, with some products carrying limited lifetime coverage. Further, the warranty on selected Yukon parts can be upgraded to a no-questions-asked lifetime warranty with our Yukon Extended Service (YES) plan. For a full rundown of Yukon warranty information click here.

USA Standard Gear offers a generous warranty program. Get more details and check out our Warranty By Product chart by clicking here.