Where the pattern falls on the gear heel to toe is not important; that is a function of the housing itself. Here is a bad pattern; the pinion is too close to the ring gear. Note the hard edge on the coast side; it looks like a shark fin. This would be very noisy and generate a lot of heat. The solution is a thinner pinion shim. Rotate the carrier and not the pinion to check the contact patch.
Use one hand to hold the pinion yoke, creating a load, and rotate the carrier four or five times in both directions. The pinion must have a load in it for the pattern to be accurate. If holding it by hand is not feasible, wrap a shop towel around the yoke and pull it tight.
This shows the contact patch between the pinion gear and ring gear. Then read the pattern. Instead, you should focus on the position between the top land and root. Where the pattern lies heel to toe is dependent on the cut of the gears themselves and the left to right position of the ring gear carrier, as well as the housing itself.
Trying to perfectly center the pattern is an exercise in futility. If the pattern is reasonably centered, it is sufficient. The pattern should be checked at least twice during the installation procedure. First, an initial check should be done, and then the final check after the rebuild has been completed to make sure nothing has changed. When the pinion depth is correct, the pattern shows smooth oval markings on both the coast and drive sides of the gear. If the pinion is too close to the ring gear, the top of the gear pattern will be smooth and rounded, while the base of the pattern will be close to the root of the gear, cutting off in a sharp line.
Certain patterns may show on one side as a teardrop or oval, with the other side cut off, even saw tooth—shaped. If the pinion gear is too far away from the ring gear centerline, the pattern rides high on the teeth, showing a smooth rounded base with a sharp line on the top.
Sometimes, there is one clean contact patch on drive or coast side, but the other side is cut off at the top.
Checking the pattern on used gear sets requires a different procedure. Ignore the drive side of the pattern; instead, concentrate on the coast pattern only. This is because the drive side already has wear from use, and the markings look like new patterns.
To start, the pinion bearing needs to be pressed off the pinion. Try to save the old bearing. Keep the original shim as well. If it is in good shape not bent , it can be reused; otherwise you need to measure it with calipers and match it up with a new one from your installation kit. If you have a hydraulic press, you can remove the bearing yourself using a bearing separator or a bearing clamshell. If the bearing came off the pinion in one piece, it can be reused for checking the pinion depth. Because you want to be able to remove the bearing to change the shims, the inner diameter of the bearing needs to be enlarged.
You can do this with a die grinder and either a flap wheel or carbide cutting tool. Holding the bearing tightly in one hand please wear gloves for this process , remove material evenly from the center of the bearing until it slides easily onto the new pinion gear. If you are changing the gears, the pinion depth needs to be set. GM and bolt units use shims behind the inner pinion bearing the large bearing inside the case. The factory provides the pinion depth specs.
You just need to do the final dial-in. You can reuse the original shim or select a new shim that matches the factory specs. If there is a large difference between them, you can simply go with a shim that splits the difference. This occurs quite often, as the factory spec and the actual gears and housing do not always work together. After the pinion depth has been set, use a hydraulic press to install the new bearing onto the pinion gear.
Make sure the bearing is fully seated. If you have not already installed new bearing races for the inner and outer pinion bearings, now is the time. Do not proceed with the original races in the housing. Clean the pinion gear with brake cleaner or parts wash to remove any protective grease. Slide the new pinion gear into the housing, install the outer pinion bearing and then the pinion yoke, followed by the pinion washer, and finally the original nut if available.
Do not install a crush sleeve at this time. Sometimes the outer pinion bearing is very tight on the yoke, and has to be pushed onto the shaft with the pinion yoke. This is a variance in the parts. Slowly thread the pinion nut onto the pinion, pulling the pinion bearings into their races. Once the bearings are fully seated and the pinion does not move in or out, apply a little more tension on the nut for a minimal amount of bearing preload.
Remember, there is no crush sleeve between the bearings, so too much load could damage the bearings. The crush sleeve installs as shown, only after the pinion is in the housing. It rests between the inner bearing and the outer bearing inside the case. This image is for reference only, the sleeve is only installed after the pinion is in the case.
The new front bearing frequently fits quite tightly to the pinion bearing. You can use the yoke to help seat it if necessary. Once the bearing has been seated, install the new seal using a soft hammer or a seal driver. Passenger car bolt seals are no longer available new, but the truck seal fits and works. Make sure that the seal is lubed with gear oil; otherwise it could tear.
The yoke goes on next and then you place the thick yoke washer on the pinion. Not much thread is visible; this is normal, as the pinion may not slide easily onto the new pinion gear. Apply high-strength thread locker to the pinion threads before placing the new pinion. Hold the yoke by hand then crank on the nut until the bearings contact the races.
Once they contact, work slowly until there is a slight drag on the yoke. It takes to ft-lbs to crush the sleeve. But once it crushes, it has to be right. Too much preload means starting over with a new sleeve. Here the yoke is locked down on the bench. If you have to use a breaker bar, you can install an axle and either lock it down with a wrench or have a helper hold it in order to crush the sleeve.
Next, the carrier and the gear should be cleaned with brake cleaner or parts wash to remove any protective grease. If you have not replaced the bearings on the carrier, now is the time to do it. The ring gear should drop right onto the carrier, and; with just a little effort, seat onto the gear flange. Secure two bolts to the ring gear and thread them in by hand.
Apply a small amount of thread locker to the rest of the bolts and thread them into the gear. Remove the two bolts used to secure the gear in position and apply threadlocker.
Reinstall the bolts. If you have an assistant, have him or her hold the carrier. If not, you can use a bench vise. The ring gear bolts must be torqued in a criss-cross star pattern to ensure that the gear is properly seated and torqued. During disassembly, you removed and labeled the carrier preload shims.
Retrieve them and prepare them for installation. If you are reusing the original carrier, it should work as is. Once the preload is close by feel, check it with an inch-pound torque wrench. You need a wrench that measures 0 to 20 in-lbs in 1-inch increments. It works. The measurement here is 6 in-lbs, which is within spec for used bearings, but new bearings need to be 14 to Once the preload is set, you can use a punch to tap the pinion nut to help keep it from backing off.
Install the carrier into the housing and hold it in position with one hand and use the other hand to slide the preload shims into the housing between the carrier bearings and the case. If you are using a new carrier, you may have to adjust the shim package. As long as the carrier is not loose side to side, the originals should be sufficient for this process.
Replace the carrier end caps and torque them to spec, which is 60 ft-lbs for all GM and bolt units. In the unlikely event that the pattern is dead-on this time around, pat yourself on the back. This does not happen often. More likely, you will need a series of trial-and-error test fittings. Once you have a baseline pattern, you can adjust it. You want to make large changes that intentionally move the pinion to the other extreme so you can see which direction you need to move if you are too close, push the pinion deeper, or vice versa.
Once the pattern is in the ballpark, you can make small adjustments to fine-tune it. A large adjustment is. If you start out making small adjustments, the process takes much longer. As you reach the correct pattern, the smaller adjustments center the pattern between the top and root of the gear teeth. Once you reach the correct pinion depth, remove the pinion gear from the housing and install the new inner bearing to the pinion gear with the correct shims. This can be done with a basic hydraulic press and a piece of heavy-wall pipe or a bearing clamshell.
Remember, do not install the new bearing until you are sure that the pinion depth is correct. Next in the process of setup is setting the initial backlash for the ring gear.
This is the amount of forward and backward headspace between the ring gear and pinion. Backlash is measured with the pinion gear installed in the housing, with minimal preload. You need a dial indicator with a magnetic base to check the backlash. Backlash is adjusted by moving the carrier left or right with shims between the carrier bearings and the axle assembly housing. Most gear sets follow these basic parameters: Moving. The sweet spot for GM and bolt backlash is between. If the backlash is too tight, the gears generate a lot of heat and burn up.
If the backlash is too loose, the gears are clunky and noisy. Almost all factory carriers are shimmed with a solid spacer that has been machined specifically for that housing. If you retain the carrier, it may work great, but it usually needs adjustment.
A shim kit that includes a pair of master spacers and a series of shims of varying thicknesses does the trick. The master spacers lock together in the center and hold the shims in the pack, making installation easier. The shim pack also provides the carrier bearing preload, but that is the last step. For now, you want the shim pack to be snug, but not tight. Use calipers to measure the original spacer and select shims from the kit to match. Try this first and add or remove shims from there.
Install the carrier into the housing, and then slide the shim packs between the bearing races and the housing. Bolt the end caps in place and torque to spec, 60 ft-lbs per bolt. Secure the pinion yoke from moving; this is a key component to checking backlash. Rotate the carrier until it contacts the pinion gear, and then zero the gauge on the indicator. The indicator dial can be zeroed anywhere on the dial.
Once the zero point is determined, rotate the carrier in the opposite direction until it contacts the pinion gear again. Read the dial. If the measurement is between. If not, the shim pack must be adjusted until the correct backlash range is reached. Once you find the correct shim load, check the backlash in at least three places on the ring gear to be certain it is correct. Record the shim sizes for each side, just in case you need to rebuild the shim pack. Proper setup of the dial indicator is crucial for getting accurate measurements.
In the case of reading backlash, you need one with a magnetic base. This allows you to position the indicator anywhere there is a ferrous magnetic surface. A typical kit will contain the indicator, the magnetic base, a couple of adjustable arms, and a case. As long as the unit is accurate to. The magnetic base must be stable and locked to the housing.
If it moves at all, the measurements will not be accurate. In addition, you need to properly tighten the clamps. Dial indicators are very useful for all kinds of automotive measurement work, but they are critical for setting up a differential. Of course, the gauge needs to be properly zeroed.
Push the needle in a bit and then zero the scale to that point. This allows you to get an accurate reading at the true zero point.
Make sure you double-check your readings. The large indicator scale has hash marks in. A smaller second gauge indicates tenths of an inch, up to 1 inch. The act of tightening the knob can take the gauge out of position. The magnet on the base is strong, but it slides easily with moderate pressure.
To properly position the indicator on the housing to take readings, follow these steps. A magnetic base is the first part of the indicator. Your kit must include one for ease of securing it to the housing. You can mount the dial indicator on any part of the center section that is clear of your work area.
You can slide it up and down as necessary. The mount on the back of the indicator attaches to the second arm. Install this loosely until the final adjustment is complete. The base also has a V shape on the bottom for round surfaces.
An adjustable angle fitting on the second arm helps get the indicator in the best position. This is a good position for taking the backlash reading. The base is solid and not wobbly and the indicator is inline with the ring gear. You want to read the gear with the indicator inline with the rotation of the gear.
The needle of the gauge should sit on the edge of the tooth without slipping off. Once the indicator is positioned, it has to be zeroed.
Each hash-mark is. Once the pinion depth and backlash have been set, check the gear pattern again. If all is well, you can move on to adjusting carrier bearing preload and pinion bearing preload, as well as installing crush sleeves.
Apply a coating of fresh gear oil to the bearings before proceeding with the final installation. The carrier bearings must have some load on them for the unit to operate correctly. All GM and bolt housings use an outside shim design for the carrier bearings.
After the backlash has been set, add equal shims to both sides until the preload is as tight as possible without damaging the shims. Carrier bearings rarely fail because of too much preload; in fact, it is difficult to load too many shims in this design without using tools. The shims should be tight, and it may help to pack the shims with the carrier halfway out of the housing and roll the assembly into position all at once.
This is the most critical component of the final assembly, and the GM design uses a crush sleeve, which is the trickiest of them all. The pinion preload is achieved by tightening the pinion nut until the bearings contact the races and then continue loading the bearings until they have reached a range of rotational torque that is measured in in-lbs.
Although this works for the experienced builder, the novice should rely on the proper tools to get the job done right. Too much preload kills bearings; not enough makes for a noisy ride. This is a special metal sleeve that crushes with to ft-lbs of torque.
This is an important step because you do not want a ring gear bolt to come loose inside the axle. For added insurance, you can even add a small amount of sealant to the ring gear bolt holes. This goes for all Loctite joints. Place some red thread sealant in the ring gear bolt holes. The ring gear is not oriented or clocked in any special way to the differential case. Make sure that the holes are lined up. By hand, pull the ring gear into position and install a couple of bolts.
Begin by starting two bolts that are opposite each other to hold the gear in place. The bolts have washers under the heads. These smaller-headed bolts with washers are used in Traction-Lok applications only.
Open differentials and most other aftermarket differentials use larger-headed ring gear bolts. Continue partially threading in the remaining bolts. By starting all of the bolts loosely, it helps to make sure that the ring gear is guided correctly onto the differential case.
Snug all of the bolts. There is no need to get them tight as the differential case is not securely anchored on the bench and just twists all over. In order to hold the differential case in place while you torque the ring gear bolts, use the homemade spline tool in a bench vise. Clamp the tool in the bench vise and set the differential in place. Make sure that the spline is engaged in the differential side gear. You can make a homemade T-shaped tool by taking some old pieces of axle shaft splines and welding them to a bar.
I will insert this into the other side gear. Now you can hold the side gear in place while you torque the ring gear bolts. While this may seem like overkill, it is an effective technique rather than trying to clamp the differential case in the vise. Clamping the case in a vise is not recommended and usually leaves gouges and stress risers, which could lead to cracking and failure.
Torque the ring gear bolts while keeping the differential from rotating. Torque them in stages to a final torque of 65 ft-lbs. You can also use a staggered star pattern to evenly draw up the gear. Take your time and do this in steps so you do not pull on the gear unevenly and risk any misalignment and potential warping or gear runout. Unlike the 8. This cast pinion cartridge allows you the freedom to adjust pinion mounting depth independent of bearing preload.
So the pinion head bearing installs without a shim underneath it. The pinion head bearing is a press fi t. Using a hydraulic press, press the bearing all the way down until it contacts the machined ledge on the pinion back face. As with the differential bearings, make sure to only press on the inner race of the bearings and not the cage. Once the bearing has been fully seated, install the solid shim left. You can upgrade to a solid shim instead of the collapsible spacer for a stiffer bearing arrangement.
There are advantages and disadvantages to the solid spacer approach. The main disadvantage is that you may have to change the shim a few times to achieve the correct preload. But once you have it, there is a solid connection between the bearings. Once the spacer is in place, start out with a. On the right, the shim is hanging on the spline but it needs to go all the way down the pinion shaft and line up with the solid spacer. Do not add any assembly lube at this time. The new Timken bearings feature a rust preventative and lubricant.
This lubricant is required for accurate torque-to-turn measurements, so you do not want to remove this lubricant or add any oil or grease. Install the pinion cartridge with its bearings in place on the pinion. This is just a matter of carefully setting the partially assembled casting on the pinion shaft with the inner surface facing toward the pinion head.
The entire pinion shaft with cartridge looks like this. While you still have a load on the assembly, rotate the cartridge and feel for the correct torque-to-turn.
For new bearings, target a torque-to-turn in the range of 13 to 15 in-lbs. For used bearings, the amount is about 7 in-lbs. If the torque-to-turn measurement is lower than the specifications, reduce the overall shim stack height. On the other hand, if the torque-to-turn is too high, add more shims to increase the overall shim height. Before driving the seal into place, make sure that it is not tipped. Use an appropriate-size seal driver and exercise care to make sure that the seal stays aligned correctly above left.
Once in place the seal lip should not have any gaps all the way around. The blue line above right is the seal lip between the driver tool and the cartridge. This is just for the initial assembly. Use a shop press to fully seat the yoke. A slight helix or twist is on the pinion splines to take up any backlash. This makes the yoke a press fit on the pinion. Note the solid spacer shim on the press plate; it was extra from the installation kit. The last part to be installed is the pinion nut.
Thread locker and sealant orange comes pre-applied on the nut threads and the bottom flange surface. These materials help prevent oil from slowly seeping under the nut. This is another reason to use a new nut each time.
If you have the solid spacer arrangement shown and it is already shimmed correctly, just tighten the nut with an impact gun. Shoot for about ft-lbs of torque. This O-ring goes in the groove on the cast cartridge. It is partially installed here; you want to chase the O-ring into the groove all the way around. Make sure that it is fully seated and not twisted. Install the pinion straddle mount bearing.
This roller bearing fits into the main gear case. Install it through the pinion cartridge hole. Gently set it in place and then fully seat it with the appropriate-diameter press tool and a few taps with a hammer on the outer race.
The metal tabbed retainer keeps this bearing in its pocket. Set it in place and use a driver tool to seat the tabs left. Take your time and make sure that the wider of the tabs are locked into the groove in the third-member casting right. Apply some assembly grease on the pinion cartridge O-ring surface.
Start with a nominal pinion shim of about. To verify the shim is correct, the ring and pinion set needs to be installed and torqued in place.
Then perform a pattern check. Torque down all the parts and do another pattern check. Make certain that the cartridge is oriented correctly.
Temporarily install the bolts. These bolts may need to be removed later to adjust the pinion cartridge shim. Even if the shim is correct, you still remove these bolts later to apply thread locker.
If the shim is not correct, then the bolts and cartridge need to be carefully removed and the shim replaced. The final torque specification for these bolts is 35 ft-lbs. Flip the gear case and set the races in place between the threaded portion of the gear case. Install the differential case with its bearings and races in place.
Set the adjuster nuts in place. Take extra care to make sure that the threads are lined up correctly. Lightly tighten the adjuster nuts.
This is just to get things started. Here you see my homemade tool, but similar production tools are also available. Apply some thread sealant to the bearing cap bolts left and install them right. Be very careful to make sure that the cap lines up with the adjuster nut threads and tighten the bolts in place.
Torque to 80 ft-lbs. Use a dial indicator with a magnetic base. Line up the dial indicator with the outside diameter of the gear tooth and zero the gauge. Look for. For used gears, aim for. If in doubt, contact your gear vendor.
The adjuster nuts are really helpful to move the ring gear back and forth. Apply gear-marking compound to a few of the gear teeth and check the pattern. Pattern-setting details are discussed in Chapter 7. If the pattern needs to be adjusted, remove the differential, adjust the pinion cartridge shim, and reset the ring gear backlash.
Then check the pattern again. This can be tedious but is crucial to a quiet and durable axle. To achieve this pattern, I had to change the pinion cartridge shim three different times, but this is typical. This required me to remove the pinion cartridge bolts and cartridge assembly from the gear case in order to exchange the shim for a different thickness.
I put white gear-marking compound on about seven teeth and regular, old, brown assembly lube grease on about three teeth because the brown makes a more identifiable footprint onto the white compound.
I rotated the pinion and provided drag on the ring gear with my other hand to achieve the contact pattern. Secure the adjuster nuts. Typically the retainer clips and adjuster nut do not line up. Always tighten the adjuster nut into the bearing cap. The bearings should be preloaded and not in clearance.
Apply thread sealant to the retainer clip screws, make sure the the steel clip is lined up, and then install the screws.
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