randys blog
How It Works: RPM Calculator
An RPM Calculator is especially valuable to those considering jumping to a bigger tire, altering their vehicle’s performance by changing ring and pinion gears, or satisfying a curiosity about their current setup. The calculator determines your engine rpm at a selected vehicle speed. What You Need to Know The RPM Calculator requires the vehicle’s gear ratio and tire height to make its calculations. Your stock gear ratio can be researched online, it may be in your vehicle’s owner’s manual, or on a tag affixed to the differential cover. If your ring and pinion gears are at hand you can count the teeth on each and use our Gear Ratio Calculator to determine the ratio. Tire height can be ascertained by another calculator on our site. It uses tire width, tire aspect ratio, a wheel diameter to provide the height in inches. If you’re contemplating upgrading to larger tires like 35, 37, or 40 inchers know that the height on the tire is a classification, not a specification. For instance a 35x12.50-17 Mickey Thompson Baja Boss M/T is 34.6 inches in circumference mounted on a 9.5-inch-wide rim… 34.8 inches in circumference on a 10-inch rim. Some tires can be nearly a half an inch off their classification so you may want to research the tire manufacturer’s website to get the most accurate info. Feeding the Numbers Armed with the correct info, it’s time to feed the ratio and tire height numbers into the calculator, select the vehicle speed you want to tabulate engine rpm at, and press the Solve button. The calculator will display the engine rpm for the selected vehicle speed in four boxes below the calculator. Each box represents a transmission type and takes into consideration how gear reduction within the transmission will impact the final engine speed readings. The boxes are labelled Auto, AOD, Manual, and 5 Speed… simply refer to the box that best matches your transmission type. Using the Calculator for Big-Tire Upgrades Use your stock set-up as a baseline before changing the formula for a larger set of tires. Calculate at a variety of vehicle speeds… especially freeway speeds. Going in you should know what your performance goal is… to replicate stock performance or enhance performance at a given speed, i.e. a trail-only rig that will not see freeway speeds very often or a rock crawler that will not be see the street at all. You will need to pre-figure the tire heights of all the tires you are considering upgrading to and have those numbers handy. Then enter your new tire diameter and adjust the gear ratio field, evaluating different gear sets until you find one that best matches your expectations. Make note of the number in the gear ratio box and you’re ready to shop ring and pinion gear sets. Yukon Re-Gear Kits Going big-tire is not as simple as bolting on those 40 inchers and hitting the road. There are cascading effects at work. Big tires impact acceleration, freeway cruising, towing capability, and many aspects of off-road performance. Yukon Re-Gear Kits allow you to restore or enhance the performance of your truck and reap the traction benefits of big tires. It’s a win-win.
How It Works: Gear Oil & Limited Slip Additives
Gear oil keeps components such as the ring and pinion gear set, spider and side gears, limited slip differentials, axles, bearings, and the like lubricated and running smooth. Friction modifiers are additives that improve the performance and efficiency of clutch style limited slip differentials. Understanding how these vital products work is key to properly maintaining your driveline so it performs in the harshest of conditions and lasts for years to come. Read this article in Español Differential Oil By The Numbers Yukon recommends non-synthetic 80W-90 GL-5 gear oil in all differentials. Oil is rated by its viscosity value. Take a multi-grade oil like an 80W90… The 80W is the viscosity value in the winter, denoted by the W, or more precisely at 0 degrees F. So, an 80W oil is more viscous than a 60W oil at 0 degrees. The second number, 90, refers to the oil’s viscosity rating at 212 degrees F, again a higher number will be more viscous at operating temperature. These numbers are also a function of thickness. So, an 80W oil is thicker than a 60W oil. Multi-grade oils are blended with polymers that slow the rate of thinning as temperatures rise while also slowing the rate of thickening as the mercury falls, determining the viscosity range of the oil. Generally speaking a thinner oil will circulate faster through the differential (or engine for motor oil) during a cold start. Conversely, a thicker oil will protect better when the diff gears generate higher temperatures. 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 because they contain soft metal parts. Yukon offers a number of gear oils in a variety of viscosities and in synthetic and non-synthetic blends. Stand-Alone Friction Modifiers Yukon Friction Modifier Additives are used when more clamping force is needed. This type of product is for clutch-type differentials like the Yukon Dura Grip only, not gear-driven limited slips like our Spartan Helical LSD. Friction modifiers are all about annoying chatter. Yukon Friction Modifier Additive guards against abnormal clutch engagement and/or disengagement (source of the chatter), ensuring the optimal friction characteristics between clutch discs are maintained. These additives can be used to compensate for worn clutches or to “tune” the performance of the clutch packs for a specific application like road racing or vehicles that see a lot of track days. It should be noted that 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. With about one-fifth the abrasive properties these store-bought products will perform like watered down versions of our stuff. These products are vital to the proper upkeep of your differential and knowing how they’re rated and how they do their job is critical to making informed maintenance decisions for your vehicle. Shop Oil & Additives
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. 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
Diagnosing Noise (Part 1)
Many things can go wrong inside a differential. Although the hints are often subtle, most impending failures give fair warning in the form of noise. Several situations can create ring-and-pinion noise. If the gears have been quiet and begin to howl, they are probably worn or wearing. If the gears howl during deceleration only, it’s possible that the pinion-bearing preload has loosened. Howling under acceleration at all speeds indicates that something in the differential — gears, pinion or carrier bearings — has worn or no longer keeps the gear alignment correct. If the gears howl while accelerating over a certain speed range, but not all speeds, it’s likely that the gears are worn due to lubrication failure or overloading. When a newly installed gear set howls, suspect the design or setup. A common problem is worn carrier bearings, as indicated by a low-pitch rumble above 20 mph. On vehicles with C-clip axles, the noise may vary while negotiating turns. Worn pinion bearings can cause whirring noises at all speeds, under deceleration and/or acceleration. Pinion bearings tend to whir, rather than rumble, because the pinion is turning several times faster (depending on gear ratio) than the carrier. Badly worn bearings can also cause howl if they do not support the gears correctly. Worn wheel bearings can be difficult to determine. A very bad wheel bearing typically makes itself heard with great clarity; it’s the bearing that is going bad, but not destroyed, that is hard to find. Turning back and forth from hard right to hard left can identify the culprit; however, I’ve been fooled by right-front wheel bearings that make noise when turning right (which heavily loads the inside-left-front wheel bearing, but also loads the outside-right-front bearing). One common situation that may not make any noise: The pinion spins, but the tires don’t rotate. Broken spider gears can render the differential immobile, and usually make a loud, crunching sound as they make their final departure. A broken ring gear will allow the differential to propel the vehicle for about eight feet at a time, then bang or grind as the section with broken teeth tries to engage the pinion. Depending on ratio, a broken pinion tooth (or teeth) will clunk about every two or three feet. A broken axle is easily determined. After it breaks, a C-clip design axle can be pulled out of the housing without unbolting anything — or may even find its own way out. On many bolt-in-design axles, the wheel will give the broken axle shaft away by cambering in at an angle. A high spot on a gear tooth may sound similar to a broken gear, but will only make noise while accelerating or decelerating, since the spot appears on just one side of the offending tooth. A high spot on the ring gear will make a heavy clicking sound about every eight feet; a high spot on the pinion makes noise every two or three feet and is much more pronounced due to its higher frequency. Whether large or small, differential noise is telling you something. Listen carefully! If in doubt, pull off the cover or remove the third member for a closer look. Catching a bad part before is ruins others is definitely worth the effort. Popular Resources: New Gear Break-In Properly Setting Preload with Side Adjusters Size Matters
How To Use A Dial Indicator
The keys to properly using a dial indicator are precision and patience. The payoff is a long-lasting driveline. The dial indicator is one of those specialized tools that has an intimidating reputation, but as with many things, understanding the components of the tool and how they work is half the game. A dial indicator typically measures the backlash of a ring and pinion gear. It can also be used to measure runout, the untrue movement (wobble) of a rotating object like an axle, cam or crankshaft journal, wheel, brake rotor, or the input shaft of a manual transaxle/transmission. Precision is important because in ring and pinion jobs we are dealing with shims that can be paper sheet thin… as thin as three thousandths of an inch. The first step to dial indicator enlightenment is understanding the workings of the tool. Anatomy Of A Dial Indicator When measuring backlash in a ring gear the placement of the dial indicator is key. High-pinion and low-pinion applications have the drive side gear teeth on different sides of the ring gear. This will determine where the dial indicator is set up because measurements are made on the drive side of the tooth. The Setup A dial indicator is like a high-tech erector set. It can be extended and articulated in an array of angles. Setting up the unit starts with the magnetic base which is placed on the housing and then all the armature is configured to position the tip at a 90-degree angle on the drive gear tooth with the plunger in proper alignment with the gear’s rotation angle. A vast majority of dial indicators have magnets that you position to align the plunger and ring gear tooth. In whatever manner the base of your dial indicator secures to the housing, it must maintain a stable platform because every proceeding step relies on the accuracy and consistency of this starting point. Here, the diff housing makes a great anchor point but other applications may not offer so obvious mounting possibilities. The arm can be moved up or down the main shaft while also being adjusted inward and outward within the housing to more precisely line up the tip and the tooth face. This is where your erector set experience comes into play. There is an adjustment knob behind the dial that allows the dial assembly and plunger to swivel to better match the actuation of the tip with the angle of the gear tooth when the ring gear is moved. The goal is to make as much of a straight line measurement as you can. Tighten everything down to limit flex and be sure the tip is resting on the tooth face… any play or preload in this area will produce false readings. Also, be sure the plunger is not rubbing against the adjacent tooth which may also result in a faulty measurement. Shop Yukon dial indicators and measuring tools here. Measuring You can measure with the existing readout or zero-out the tool by loosening the bezel clamp and rotating the bezel. When measuring backlash on a ring gear be sure you’re only turning the gear and not the pinion which may influence the readout. Clamping or otherwise isolating the pinion is a good idea. When measuring a ring gear, the gear is rotated in both directions to produce freeplay. The amount of the movement is measured as straight-line travel by the tip and plunger. Even the runout of a ring gear can be evaluated by measuring the amount of movement the gear produces back and forth between the thrust bushings. Reading The Dial Most dial indicators have a one-inch stroke, meaning the plunger will only move one inch within the tool. The dial indicator’s range is denoted in the dial. The dial also has units of measure or accuracy indicated, typically in drivetrain operations a 1/1000 of an inch is the preferred unit. The main or outer dial is joined by the smaller revolution counter dial which indicates how many times the needle has gone around the outer dial. So, if the main needle travels around the outer dial twice the revolution dial will read 2. Or 0.200 inches. If the larger needle progresses past zero to 30 on the big dial, the total reading is 0.230 or 230 thousandths of an inch. Total Movement The amount of positive movement and negative movement indicated reveals the total movement. So, the measurement is made from the static beginning with the plunger engaged then it moves inward and outward and the number of units measured in each direction are added together. For instance, if the needle moves from plus five thousandths of an inch to minus 90 thousandths of an inch, the total needle movement is 15 thousandths of an inch. Additionally, if the needle moves 10 thousandths of an inch to the negative side and then five thousandths of an inch to the positive side the total movement is again 15 thousandths of an inch. Once you successfully set up the dial indicator measuring other gear sets will be super easy as long as they have the same pinion arrangement i.e. high pinion or low pinion, as the basic setup of the tool’s armature has been established and you’ll only need to fine tune the tip-to-tooth relationship. Dial indicators deserve a place of honor in your tool case. They expand our capacity, allowing us to do more jobs. They add quality to our work, by enhancing the accuracy of our actions. The end result is a job better done that will last for years to come, a win-win in anyone’s book. Shop Yukon Differential Tools
Subscribe To Our Newsletter
Sign up & unlock 5% off. Get news on insider deals, product releases, and expert advice.
