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Understanding Thick Ring Gears & Carrier Breaks
A carrier break is 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 must 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. Shop Ring & Pinion Gear Sets Thick Ring Gear Case Study We will be looking at two gear sets for the GM 12T differential. The 3.73:1 set is the maximum numeric size that the stock carrier can handle…. Going to a 4.11 breaks the bank, and the carrier. The size of the pinion gear head is the linchpin. As the numeric size of the gear goes up the pinion size decreases, until the point when it can no longer properly engage the ring gear. The 12T 3.73 set features an 11-tooth pinion and the 4.11 sports a nine-tooth pinion which is too small in diameter for proper engagement so the 4.11 kit has a thicker ring gear to make up the difference and provide proper engagement. In some instances, a thinner ring gear may be needed to stay within deck height specs. The break point is typically determined by the placement of the carrier case and the pinion centerline, and those are really arbitrary and up to the whim of a design engineer. We do NOT recommend ring gear spacers in any situation. Remember that using a thick or thin gear set has no side effects and will be just as strong and hold up just as well as a gear set that is the factory thickness. The chart below illustrate the break points and deck height parameters of many of the most popular carrier/differentials.
The Ultimate Gear Break-In Guide: Ensuring Peak Performance and Longevity
Gear break-in is a crucial process that involves controlled heat cycling of the gear set to properly season and harden the contact surfaces as well as to polish and establish the final contact pattern on the gear face. It is essentially a series of test drives that play a vital role in ensuring the long-term durability and optimal performance of the gears. Neglecting or improperly conducting the break-in procedure can lead to damaged or failing gears, necessitating a complete re-do of the installation. Even after the gear installation is completed, with correct backlash and preload settings, the break-in process is a make-it-or-break-it proposition. This involves driving the vehicle on urban roads and freeways, as different vehicle speed ranges induce varying levels of heat cycling. Additionally, if towing is part of your intended use, an additional round of break-in is necessary. Towing puts additional pressure on the pinion and slightly alters its position on the ring gear teeth. By subjecting the gears to this towing-induced stress during the break-in period, you effectively harden and condition the specific areas of the gear teeth that come into contact under towing conditions. Proper Gear Break-In: 5 Essential Steps Properly conducting the gear break-in process is of utmost importance, as it can make a significant difference between encountering gear-related issues down the line and enjoying trouble-free driving for years to come. By adhering to the recommended break-in procedures, including the specific requirements for towing, you ensure that the gears are thoroughly seasoned and hardened, promoting their longevity and reliability. To ensure the proper break-in of new gear sets and prevent overheating damage, it is crucial to follow these guidelines: 1) Drive light-footed at low speeds for the first 15 to 20 miles: Take it easy and baby the vehicle during the initial 15 to 20 miles. Afterward, stop and allow the differential to cool down before continuing. Repeat to 100 miles. 2) Avoid heavy acceleration: During the first 100 miles of the break-in period, avoid any sudden or extreme acceleration and steep hills, as this can put excessive stress on the gears. 3) Change the gear oil after the first 500 miles: After driving approximately 500 miles, it is advisable to change the gear oil. This helps remove any metal particles or phosphoric coating that may have been shed by the gear set during the break-in period. 4) Drive at least 500 miles before towing: To retain the warranty on the gears, it is recommended to drive the vehicle for a minimum of 500 miles before towing any heavy loads. 5) Break in the gears when towing for the first time: If you need to tow a load for the first time, follow this procedure: Drive a very short distance (less than 15 miles) with the full load, then stop. Allow the differential to cool for approximately 20 minutes before proceeding. Repeat this process two more times, covering a total distance of approximately 45 miles, to fully break in the gears. Shop Ring & Pinion Gear Sets By adhering to these guidelines, you can ensure a proper break-in of your new gear sets and minimize the risk of overheating damage. It's important to follow these recommendations to maintain the warranty on the gears and promote their longevity and optimal performance. How Hot is Hot? We’re not talking about judging the temperature by touch. Most people find it difficult to hold a cup of coffee that is at 140°F, and a shower at 120°F can cause scalding. To obtain more precise temperature readings, we recommend using a handheld infrared digital thermometer, which can be purchased for $15 to $50 at most any auto parts store. By using this tool, you can determine the temperature more accurately and refer to the chart below to determine the appropriate oil change interval. During the break-in period, it is normal for new differentials to run at temperatures ranging from 250°F to 275°F. It is crucial to avoid towing or embarking on long road trips during the first 500 miles, as these activities generate additional heat. If the differential reaches a temperature of 300°F, it is considered too hot, and it should be allowed to cool down. Once the break-in period is completed, the normal operating temperature for a differential in a vehicle with stock trim and regular driving conditions is between 170°F to 220°F. However, for vehicles equipped with large tires, undersized differentials, or engaged in towing, the normal operating temperature ranges from 200°F to 250°F. Remember that a new gear break-in requires an oil change at 500 miles to ensure optimal performance and longevity of the differential. Use your findings in the chart below to determine your oil change interval. Temp Reference / Oil Change Frequency Chart TEMPERATURE FREQUENCY 170° 100,000 Miles 200° 50,000 Miles 220° 25,000 Miles 240° 12,000 Miles 260° 5,000 Miles 260°-320° 500-1,000 Miles [until temp is controlled] Mistreated & Overheated: How Improper Gear Break-In Kills Your Gears When examining the accompanying images of mistreated and overheated gears, several key factors come into focus. One of the most significant is the process of gear meshing during a correct break-in procedure. As temperature rises and pressure is applied, these forces work to harden and compress the grain structure, effectively smoothing the surfaces of the gear teeth. However, in the images provided, the teeth appear coarse and exhibit an exposed grain structure, indicating insufficient break-in. Another crucial but often overlooked aspect is the role of the oil in the cooling down process, known as "quenching" the gears. Similar to the technique used in knife making, where super-heated metal is rapidly cooled in an oil bath, this process alters the surface metallurgy of the gears. However, in gear break-in, we aim to avoid extreme heat like that used in knife manufacturing. This heating and cooling cycle is repeated during the drive cycles of the break-in period, contributing to the gear's overall durability. Breaking in deep gears on a small differential can be challenging due to reduced contact area and less metal in the pinion head to act as a heatsink. Excessive heat during the break-in period can also cause the hard face built up through initial break-in to peel away under gear meshing, leading to changes in backlash. This fracture and peeling off of the hard face exposes a rough grain structure, essentially reverting the metal back to its pre-break-in condition. Subsequently, the gear break-in process restarts with even rougher gears, creating a downward spiral. Additionally, gear geometry is altered as the teeth become thinner and smaller, further exacerbating the issue. While adjusting backlash may address one variable, it fails to address the underlying problem. The burnt ring gear pictured above shows the telltale signs of heat damage due to improper break-in: Coarse grain structure (red ovals) on the teeth where there should be a mirror-like finish and fracturing across the face (yellow arrows). Another frequently disregarded concern is the cooling airflow from underneath the vehicle. At highway speeds, the airflow around the differential can become stagnant. Surprisingly, overheating gear sets often result not from actual overloading but from driving at high speeds for extended periods too early in the break-in process. Light throttle cruising at freeway speeds, although seemingly gentle on the parts, can generate more heat than the differential can dissipate. This particular scenario accounts for a significant number of gear set failures during the break-in phase. Based on these observations, it is recommended to use a quality 80-90 GL5-rated conventional gear oil during the break-in period. If there is a suspicion of overheating, changing the oil is advisable since conventional gear oil is relatively inexpensive. It's essential to remember that differentials lack internal filtration, making regular draining, cleaning, and refilling necessary to remove wear particles. Additionally, conventional gear oil possesses distinct properties that facilitate effective gear "quenching," maintaining viscosity better and adhering to parts more effectively compared to synthetic oils. In conclusion, proper gear break-in is a critical to carefree motoring. By following these guidelines and understanding the intricacies of gear break-in, owners can ensure the longevity, reliability, and performance of their gears, mitigating the risks associated with improper break-in practices. Shop Ring & Pinion Gear Sets
How It Works: The Pros and Cons of Spools & Mini Spools
Spools are all about getting full lockup on a budget… 100% lockup 100% of the time. There are two types of spools: full spools and mini spools. Each attains the same objective, ensuring both drive wheels on a given axle receive full torque and rotate at the same speed all the time. They create a solid axle. The Spool Compromise As with any drastic, all-in type of modification, there are compromises along the way. The spool is no different. Since the axles are locked there is no allowance for situations where the tires need to spin at a different speed… i.e. when the vehicle turns a corner. When this happens the tires chirp, sometimes aggressively, as they struggle to complete the turn. The rubber is the weak link. It’s what gives to allow the vehicle to maneuver. In doing so tires absorb a lot of abuse in the form of significant wear. One should also remember even when not pushed to the level of chirping, any imbalance in wheel speed is scrubbed off by the tires resulting in tire wear. Simply put, spools chew up tires. Another compromise is how the binding within the differential also produces undue stress on the axles themselves. In the long term, axles can bent out of shape because of the torsional stress they are subjected to on the street. Changing Driving Dynamics There is a cause-and-effect scenario going on here. In most cases, running a spool will compromise the turning radius of the vehicle. Further, a spooled driveline can be unforgiving driving on wet/snowy roads as it lacks the finesse to handle conditions that call for the management of different wheel speeds to ensure vehicle stability and control. You can roam the online forums and the street-worthiness of a spool-equipped vehicle is a long-raging debate. Due to their unwieldy nature, we recommend spools as an outstanding choice for dedicated off-road and drag racing vehicles only. Full Spool A full spool replaces the carrier, spider, and side gears. The unit consists of a snout and a ring flange. The axles are installed in the snout, which is splined to accept the axle shafts. The spool’s ring flange bolts onto the ring gear. So, the ring and pinion do their job, redirecting torque 90 degrees from the driveshaft to the wheels but the housing has lost its ability to differentiate wheel speeds between the wheels. Yukon and USA Standard Gear spools are made from high-quality 8620 steel and heat-treated for additional strength so your differential is ready for extreme action in the name of ultimate traction. Mini Spool A mini spool is less expensive than a full spool. Since it swaps in place of the spider gears and side gears installation is easier, faster, and cheaper than a full spool. Though Yukon and USA Standard Gear mini spools are constructed from heat-treated 8620 alloy steel they are not as stout as full spools because minis rely on the factory carrier for strength. Cost Versus Reward We see our spools as a safer option for those who are considering welding their gears together to get the same solid-axle traction. The big problem is that welding can be done poorly and fail. Either by weak welds or too much heat which compromises the grain structure of the steel causing the gears to become brittle at the weld point and eventually break. When welded diffs let go they can take other components out… which negates any cost savings of welding. In our eyes, spools are only for dedicated off-road and drag racing vehicles. If the vehicle will see the street we urge customers to consider stepping up to a locker or limited slip differential. Cost Versus Capability You can opt for a Spartan Locker, a helical positraction LSD, or a locker. While each of these products represents a step up in streetability, they also embody a rise in cost. A full spool runs around $320 to $375. A Spartan Locker checks in at $400 to $500, provides full lockup, and although it may click occasionally it is far more civilized than a spool. Our helical positraction limited slip differentials start at $600, seamlessly enhance traction on the street, but do not provide full lockup. Yukon’s Grizzly Locker, an automatic locker / mechanical locker, starts at about $780 and delivers 100% lockup and the ability to automatically unlock when needed. Of course, pricing is application-dependent, but for very little extra investment you can get a Spartan Locker or helical LSD. In many cases, you will save money in the long run by not shredding and buying new tires on the regular. If you run expensive big tires like 35-, 37-, or 40-inchers the savings could be substantial. Spools do what they’re intended to do and we build ours with quality materials and top-notch craftsmanship. But these products are narrowly focused on dedicated purpose-built vehicles that aren’t expected to be driven on the street or even make a 90-degree turn. Seriously consider your vehicle’s usage expectations and consider more than the initial cost. Look down the road, moving up to a more versatile, driver-friendly traction device can be the best call for your wallet and your nerves. Shop Spools
How It Works: Dropout Vs. Carrier-Type Differentials
A pumpkin is a pumpkin, right? We’re talking about differential housings, not jack-o’-lanterns, and hold your horses - all are not created equal in the eyes of the drivetrain gods. While diff housings all do the same basic thing: house the gears that make forward motion possible, there are two different designs at work here. Dropout Differentials Dropout differentials, also known as third members, can be readily identified by their removable front center section. The ring and pinion gear set in a dropout diff is contained within a carrier assembly that can be removed or dropped out for easy access. The iconic Ford 9-inch is a dropout or third member type of differential and GM, Toyota, and Chrysler also offer dropout diffs. The ribbed housing is a quick giveaway that this is a Ford 9-inch. Along with the OE Ford 9-inch, there are tons of custom aftermarket Ford 9-inch configurations. The General has dropouts but many of them date back to the 1950s and are not relevant today. Toyota dropout-style diffs consist of the 7.5” rear, 8” rear, 8” high pinion, 8” clamshell, 7.5”, 8.5”, T100 IFS, and numerous 9”, 9.5”, and 10” offerings. In the Mopar world dropout differentials are called banjo-style diffs because someone thought the assembly, when pictured with an axle shaft, had the look of the infamous stringed musical instrument. The Chrysler 8.75” is the automaker’s most popular dropout-style diff. Of course, Dana manufactures a number of dropout style diffs that appear in vehicles across numerous brands. In some circles a front-loading dropout-type diff is known as a pig-style diff. While on the subject of slang, our friends across the pond call the ring gear a “crown wheel” … hey, as long as we’re on the same page it’s all good. Perhaps the main inherent advantage of a dropout diff is easy gear swaps. The gear swap advantage boils down to where you do the work. Since the gear case center section can be unbolted and removed, all the ring and pinion gear installation and tedious setup can be done away from the vehicle on a workbench. It’s more comfortable and access to, and applying leverage on, the key components is much easier. Shop Dropout Housings Shop Complete Differentials/Third Members Carrier Differentials Carrier differentials have a cover on the backside of the pumpkin that is unbolted to gain access to the ring and pinion gears and other internal workings of the diff. GM’s 10-bolt and 12-bolt differentials are common examples of carrier-style diffs, which may be referred to as Salisbury differentials by those who speak the Queen’s English. The fact that the gears are visible on the backside of the housing is a telltale sign this is a carrier-type differential. Carrier-type differentials are more popular and they have some strengths when compared to a dropout diff. Troubleshooting is one. Looking for broken or worn parts in a carrier diff is as easy as removing the back cover where in a dropout you have to commit to a full gear case removal to see what’s going on. It should be noted that some custom aftermarket dropout diffs have rear inspection covers to address this concern. There is a less common concern for carrier diff drivers who wheel on the weekends; the diff cover. Traversing craggy terrain can result in the stock diff cover being peeled back like a can of sardines. A protruding rock or tree stump can also spell doom by way of impact damage. The answer: Yukon Hardcore Performance Diff Covers. They look great and are constructed from thick-walled high strength nodular steel to protect lockers, gears, and axles from extreme impacts as well as deflection caused by flex in the housing. Hardcore Performance Diff Covers come with a durable powder coat finish, magnetic drain plug, quality gasket, and high-strength steel fasteners for easy bolt-on installation. Knowing what dropout and carrier-type differentials are and a general idea how they work will help you make more informed installation decisions as you have the knowledge and vocabulary to talk straight with your mechanic. Shop Re-Gear Kits
Lock & Load With Yukon Traction Devices – Dura Grip LSD, Zip Locker, Grizzly Locker
Yukon has tried-and-proven traction devices designed to handle all types of tough terrain. Choose from the Yukon Dura Grip limited slip differential, Yukon Zip Locker, or the Yukon Grizzly Locker. In order to make a more informed choice here are some factors to consider when looking at traction adders. Differences Between LSDs & Lockers In their static state limited slip differentials are pre-loaded and provide traction to both wheels. When the LSD is further loaded… under acceleration, in a fast corner, or when wheel slippage occurs off-road, the clutch packs 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. 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 than limited slips. Limited slip differentials do not generate 100% lock-up. They do not require activation from the driver. Their engagement is mechanical, a reaction to driving conditions, namely load and wheel slippage as mentioned above. Yukon Dura Grip LSD The Yukon Dura Grip is a great choice for transforming an open, one-legged differential into a highly capable diff that can provide two-wheel grip when needed. Engineered for long life and completely rebuildable, Dura Grips feature a high-strength nodular case, forged 4320 chromoly spider gears, and composite clutches. In clutch-type LSDs like the Dura Grip, 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 and they 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. Rebuilding a Dura Grip 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. Shop Yukon Dura Grip LSD Differences Between Yukon Zip & Grizzly Lockers The big difference between these two lockers is actuation. The Yukon Zip Locker is an air-actuated locker and the Grizzly is a mechanical locker. An advantage of an air-type like the Zip Locker is choosing when to engage the unit and its superior on-road performance. A con is the need to purchase and plumb an air system in order to engage the locker. Mechanical lockers like the Grizzly (pictured at left) are always activated which means they are providing 100% lock up all the time, including on the road to and from your favorite trail or on your daily commute. On-throttle driving conditions, where load is applied to the differential, induces locking. Off-throttle situations, where the diff is unloaded, leads to a partially unlocked unit. When the vehicle turns and the two wheels on the axle turn at different speeds, the unit makes a clicking sound as the square-cut side gears move over and past one another. This ratcheting sound can be loud and is why mechanical units may not be best suited for vehicles that spend a lot of time on the street… it all depends on how sensitive your ears are. The bottom line is Yukon is your one-stop traction destination because we have products for all levels of performance from commuter/weekend warriors looking for a moderate upgrade to dedicated rock crawlers or drag racers that demand bear claw traction. Shop Yukon Zip Lockers Shop Yukon Grizzly Lockers