This is where you combine the assembled differential with the gear case and hypoid gears. Plus, you also add the necessary bearings, seals, and shims.
You can purchase individual pieces or a complete kit that includes everything that you need.
Step-1: Inspect Component Kit
Use the large shims on the left to make pinion mounting distance adjustments. The bearings just below them are the differential case bearings. The bearings at the upper right are the pinion straddle mount, head, and tail bearings with the solid shims and retainer next to that. The rest of the pieces are miscellaneous seals, pinion nut, gear marking compound, and thread sealant.
This Tech Tip is From the Full Book, FORD DIFFERENTIALS: HOW TO REBUILD THE 8.8 AND 9 INCH. For a comprehensive guide on this entire subject you can visit this link:
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Step-2: Lay Out Parts (Important!)
Make sure that everything is accounted for and that everything is clean and prepped for fi nal assembly. Notice that I have already pressed in the pinion bearing races in the pinion cartridge.
Step-3: Install Differential Bearings (Professional Mechanic Tip)
Press the differential bearing onto the differential case. It is a press fit, so you can use a hydraulic press (shown) or an arbor press. Make sure that you install the bearing in the correct orientation. The smaller diameter should point toward the outside of the differential. Be careful to only press on the bearing inner race. I like to use an actual inner race where the cage and rollers have been removed. This is where it is nice to save old, damaged bearing races, as they make perfect press tools.
Step-4: Start Ring Gear Installation
The hypoid ring gear has a slight press fi t and is held in place with ten bolts.
Step-5: Apply Thread Locker to Ring Gear Bolts
Use solvent and brush to thoroughly clean the threads of the bolts and ring gear holes. You want to ensure that all oil and debris have been removed. Apply thread sealant (Loctite) to the first few threads of the ring gear bolts. 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.)
Step-6: Place Differential Case over Ring Gear
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.
Step-7: Install Ring Gear
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.
Step-8: Install 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.
Step-9: Set Differential in Spline Tool
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.
Step-10: Secure Differential in Vise (Professional Mechanic Tip, Special Tool)
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.
Step-11: Torque Ring Gear Bolts (Torque Fasteners)
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.
Step-12: Install Pinion Gear
Unlike the 8.8-inch pinion, the 9-inch style utilizes a removable pinion cartridge. 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.
Step-12: Install Pinion Gear (Continued)
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 .012-inch shim. 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.
Step-13: Set Pinion Tail Bearing into Pinion Cartridge
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.
Step-14: Install Pinion Cartridge
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.
Step-15: Press In Pinion Tail Bearing
While you still have a load on the assembly, rotate the cartridge and feel for the correct torque-to-turn. If you don’t have experience doing this, you just need to install the flange and nut, then you can measure the torque-to-turn while holding the pinion cartridge in a vise.
Step-16: Test Torque of Pinion Assembly (Precision Measurement)
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.
Step-17: Install Pinion Seal
Now that the correct pinion bearing preload has been reached and verifyed by torque-to-turn measurements, it’s time to install the pinion seal. Before driving the seal into place, make sure that it is not tipped.
Step-17 (Continued): Install Pinion Seal (Special Tool)
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.
Before installing the pinion flange, apply a small amount of grease to the seal surface of the pinion yoke, so the seal is never dry and doesn’t burn up prior to adequate lube getting to it. This is just for the initial assembly.
Step-18: Seat Yoke onto Pinion Shaft
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.
Step-19: Install Pinion Nut
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 220 ft-lbs of torque.
Step-20: Install O-Ring
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.
Step-21: Install Pinion Bearing
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.
Step-22: Set Bearing Retainer in Place
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).
Step-23: Apply Assembly Grease
Apply some assembly grease on the pinion cartridge O-ring surface. This makes sure that the O-ring doesn’t get damaged during installation of the cartridge.
Step-24: Install Pinion Cartridge (Important!)
Start with a nominal pinion shim of about .014 inch. 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.
Step-24: Install Cartridge (Continued)
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.
Step-25: Install Differential Unit
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.
Step-26: Set Adjuster Nuts
Set the adjuster nuts in place. Take extra care to make sure that the threads are lined up correctly.
Step-27: Tighten Adjuster Nuts
Lightly tighten the adjuster nuts. This is just to get things started. You really can’t go much beyond finger tight as the top of the bearing cap is not in place yet. (Here you see my homemade tool, but similar production tools are also available.)
Step-28: Install Bearing Caps
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. Don’t forget to check that you set the correct caps as marked previously for left and right. Torque to 80 ft-lbs.
Step-29: Set Ring Gear Backlash (Precision Measurement)
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 .010 to .016 inch for OEM gears and .007 to .010 inch for aftermarket gears. For used gears, aim for .010. (If in doubt, contact your gear vendor.) The adjuster nuts are really helpful to move the ring gear back and forth. Unlike the 8.8-inch axle that requires unique shims every time, just loosen one side and tighten the opposite side to move the gear.
Step-30: Apply Gear-Marking Compound (Critical Inspection)
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.
Step-31: Install Adjuster Keepers
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.
Step-32: Torque Down Retainer Clips
Lightly tap the retainer clips to make sure that the tang is in place. Torque the retainer clip screws to 20 ft-lbs. Remove the pinion cartridge bolts one last time to apply thread sealant. Only remove and apply to one bolt at a time because you don’t want the pinion to come loose. Torque the pinion cartridge bolts to 35 ft-lbs.
Axle Housing Assembly
You’re at the point in the process where the differential has been completely assembled. Also, the third member has been completely assembled with the hypoid gears, bearings, and differential. Now you can proceed to the axle housing assembly process. Once you get the housing prepped, you can install the third member.
Third-Member Installation Step by Step
Step-1: Double-Check Axle Lengths (if custom)
If you want to use a custom-width axle, the shop that fabricates the unit needs to take some final measurements to make sure all dimensions are correct. The homemade fixture is set in place to replicate the differential pin retainer block (left). A magnet has been epoxied to the inside of the case, which is a great idea to keep any debris from circulating through the axle. Then a set of fixtures is installed on the wheel-end side of the housing, along with the axle shafts. Once everything is in place a slight clearance from the end of the axle shafts and the fixture should be present (right). Of course, the overall axle width, shock and spring brackets, and any other bracketry are all checked dimensionally and compared to the custom build sheet. If you are rebuilding an axle and you’ve already verified the dimensions, none of this is required.
Step-2: Apply RTV
Apply a bead of black RTV on the axle housing and make sure to circle the studs. Then set the paper gasket in place and follow with an additional bead of RTV.
Step-3: Install Third Member
Carefully lower the third member in place. It weighs 85 pounds, so it requires some strength to handle and install. If you’re not comfortable installing it yourself, have a helper give you a hand. The studs are a great to help align the unit but you still want to set it in place slowly and carefully.
Step-4: Install Washers (Torque Fasteners)
From the factory, copper washers were placed underneath the nuts for the third member. Most of the time, the original copper washers are long gone but you do want a soft material under these nuts (left). In the aftermarket, aluminum washers are an easy and common replacement. The third member is just a rough casting and not machined or spot faced under these fasteners. The soft washer conforms to the raw casting variations. You can also use nylonstyle lock nuts, just to be safe (right). Torque these ten nuts in a crisscross pattern in stages. First snug them all in place, then torque to 20 ft-lbs, and finally to 40 ft-lbs.
Of course, one telltale sign that you have a 9-inch axle is that the bottom third-member nuts cannot be accessed with a socket. For these you have to use an open-style wrench and your judgment on the correct feel of the final torque.
Step-5: Replace Wheel Studs
If you have new axle shafts, the studs are not typically installed. Even if you are going to use old axle shafts, replacing the studs with fresh ones is a good idea. This is a unique press that was made just to push the studs in place. You can achieve the same arrangement with a socket on the bottom side of the axle shaft and using a hammer to seat the stud. Just be careful and make sure that the stud is driven in straight. Some aftermarket axle shafts have threaded-in studs, which makes this step very easy.
Step-6: Inspect Axle Shaft
The finished axle shaft with the studs in place should look like this. Note the hole on the top of the flange. This is the access hole for the axle shaft retainer nuts.
Step-7: Install Wheel Bearing Parts
For a typical, sealed, large bearing wheel end retention you install the bearing retaining plate on the axle shaft first with the disc brake spacing lip pointing up. Then install the sealed ball bearing and the lock ring (if applicable). You need to press the lock ring and bearing all the way down to the positive stop on the axle shaft. This requires a fair amount of press force.
Step-8: Install Bearing and Lock Ring
Place the components in a hydraulic press and press them together (left). Use a spacer under the lock ring and on top of the axle shaft for support and to press against. Once fully seated, the shaft should look like this (right). The retainer plate is trapped on the shaft now but free to fl oat around until it is bolted to the axle housing.
Step-9: Install Seal into Axle Housing
In small or large bearing wheel-end applications, when a sealed ball bearing is being utilized, install the seal into the axle housing end (left). These seals keep the gear oil in the axle tube and contaminants out, but the bearing seals do not necessarily keep hot gear oil from passing the seal. If you are using the sealed ball style of wheel bearing, don’t forget this step and make sure that the seal is installed straight and fully seated (right).
Step-10: Apply Grease on Seal
Place a coat of lithium-based grease on the seal as well as on the inside of the housing ends (left). This helps lubricate the seal during initial running and helps the axle slide in place. For good measure, also apply grease to the seal running surface on the axle shaft (right).
Step-11: Install T-Shaped Bolts
Four T-shaped bolts go into the axle flange (left). Because they are T-shaped, they do not rotate when you tighten the nuts on the other side. These bolts hold the brake backing plate and axle retainer plate in place (right).
Step-12: Install Brake Backing Plate (Important!)
Install the brake backing plate and thread in the bolts loosely hold it in place (left). This hardware is for a typical aftermarket disc brake arrangement with a combined parking brake inside the rotor. These brake shoes are cable actuated, and that’s why you don’t see a hydraulic wheel cylinder. Apply some grease on the seal surface of the axle shaft (to aid in installation) then carefully install the axle shaft (right). Be very careful to support the axle and not drag the spline over the seal surface.
Step-13: Align Axle Shaft with Differential Splines (Professional Mechanic Tip, Torque Fasteners)
The axle shaft splines may be a little tricky to get aligned in the differential side. Take your time and tip the shaft until the splines line up. You may have to lightly tap the axle shaft to fully seat the splines. Then reach through the access hole in the axle flange to line up the retainer plate with the bolts (left). This is tricky as bolts can fall back out. Once you have them lined up, install the four nuts (middle). Tighten the 3/8-inch torque prevailing nuts to 35 ft-lbs (right). Repeat this procedure for the opposite side.
Step-14: Install Wheel End Bearings
The assembly process for a tapered-roller, bigbearing wheel end is similar to that of a ballbearing style, but there are a couple of differences. The tapered-roller, big-bearing style is not sealed but shares the oil with the axle. Do not install a seal in the axle housing or the bearing will be starved of oil. The bearing comes pre-assembled (left) with a pre-lubed bearing and seal as one unit plus the axle-retaining ring. These take the place of a ball bearing. There is still a retention plate and in some cases, a brake specific spacer ring is required on the axle shaft. So when you install these on the axle shaft, they go in the following order: retaining plate, spacer ring, seal/bearing (with seal toward the spacer ring), and retaining ring. The right photo shows the bearing/seal assembly taken apart. The seal outside diameter is a slip-fit in the axle housing end and when you tighten the T-bolts in place, it draws the whole assembly into a preloaded condition. This preload causes the outer diameter of the seal to expand and seal into the housing. This is a very robust wheel end bearing, but it’s tricky to disassemble. You can re-use the seal, but be very careful when getting the already expanded outside diameter in the housing. If you need to replace the seal, it is best to replace the entire bearing unit.
Step-15: Install Brake Rotor
Finally, set the brake rotor and caliper in place (left). An aftermarket disc setup is shown here, but the steps are very similar for a drum-style arrangement. I recommend applying thread sealant to the caliper bolts before they are installed (right).
Written by Joe Palazzolo and Republished with Permission of CarTech Inc