Product Review by Jon Hanna (Admin)

AUSSIE LOCKER Following are my notes from installing an Aussie Locker from Torq Masters into my Dana 44 front end. The unit itself is well made and very stout. The instructions are detailed and well thought out. They don’t leave you scratching your head trying to figure them out like many product sheets. The install went very smoothly and would probably have taken half a day if I hadn’t also been taking photos and setting up new gears. I ran into only one issue and that was with my existing parts, not the locker. Hopefully my experience will help you avoid the same problem. In addition the tech support (Bill Cole in particular) was very responsive in helping me track down and solve the problem. Trail Review: A couple of weeks after writing this article I was finally able to get out on the trail and really see what it could do. My test trail was Lower Terminator because it’s fairly technical (rated 3-4 depending on conditions) and I’ve been on it several times before. I was familiar with the obstacles that had given me problems in the past and was curious to see how my new Aussie Locker would handle them.I can tell you right now that I’m not going back to an unlocked rig. I upgraded from a factory limited slip to the Aussie Locker and the difference was amazing. I imagine going from an open differential would be that much more impressive. The extra traction meant I was able to use much less throttle and much more finess. Obstacles that took me several attempts in the past were conquered in a single try. And all of this is still with my rear end unlocked. One item of note is the affect on steering. It’s minimal, but there (at least on my install). I can definitely tell the difference now between driving down a dirt road in 2 and 4 wheel drive. Also, in the rocks the wheel tends to fight you a little more. I don’t consider the affect severe enough to be a negative, but rather just something to get used to and keep in mind. Overall I’m very happy with the Aussie Locker. It’s easy to install, performs great and for about $230 it’s an excellent value.
A few notes before you begin. The Aussie Locker is designed to be installed in an open carrier. If you have a limited slip differential (ie. the factory installed Trac-Lock) you’ll need to switch to an open carrier. See the end of this article for more info. This article assumes you will be reusing your old carrier, ring & pinion gears and bearings. That way everything can go back in the way it came out and you won’t need to setup new gears, which is a much more involved process. Look for a separate tech article in the near future on new gear setup. Because of the length of this article I’ve split it up into a few sections: Differential Disassembly – The basics on pulling your axle shafts and carrier so you can install the Aussie Locker. Examination of the Parts – Checking your existing parts to be sure they’re still in good shape. Checking Case Tolerances – A partial install of the locker in the carrier so you can double check the tolerances. Preparing the Remainder of the Parts – Installing the rest of the locker and getting the carrier assembly ready to go back in. Reassembly – Putting the carrier/locker back in your front end and testing it out.
Parts Overview:
	When you open the box you’ll find (2) cam gears, (2) axle gears, (2) spacers, (4) pins and (4) springs. Also included is the installation manual and Operator’s Guide.
Differential Disassembly:
Here’s what a few deep water crossings will give you. Hopefully your gear oil looks a little clearer than this.	Park on a level surface. Put the transmission in gear (or park) and chock the rear tires. Raise the front axle with a floor jack and secure jack stands under each end. Place a drain pan under the differential and remove the cover bolts, which should start the flud draining. Let it drain while you work on taking out the axle shafts.First remove both tires and then disassemble the locking hubs. If you have disc brakes remove the calipers, hub/rotors, sprindles and backing plates. If you have drum brakes remove the drums, shoes and backing plates. You should now be down to the bare knuckles on both sides and can pull out each axle shaft.
	By now the differential should be completely drained. Finish removing the cover if you haven’t already. Inspect the gear and inside of the housing for any metal shavings or damage.
	Now take a look at the pinion shaft (cross shaft) in relationship to the ring gear. If the ring gear is thin enough you may be able to slide the shaft out past the teeth, which means you don’t have to take the carrier out of the housing. But typically with a Dana 44 the ring gear is too thick and so the carrier has to come out and the ring gear removed. (See photo)
	Before you remove the carrier side bearing caps you need to mark them. They need to be reinstalled in exactly the same way they came out. You can’t turn them over or switch sides. If they haven’t been marked by the factory or a previous owner (see photo for example) then you’ll need to mark them with a punch or dremel.Next loosen the cap bolts, but leave them just a few turns from coming all the way out. Now pry and wiggle the bearing caps away from the carrier, being careful not to damage the races. Leaving the caps loosely attached will allow you to pry the carrier most of the way out, but also keep it from suddenly falling out and dropping on the floor (or your toes).
	Now it’s time to remove the actual carrier. This can seem like the most difficult part of the whole process. Most carriers take a lot of determination and some really choice words to get out. Start by using a large prybar, but be careful not to pry against the ring gear teeth or inner spider gears. You might try a chain or strap wrapped around the carrier. Then you can slip the prybar through the strap and leverage against the axle housing instead of the carrier or gears. One trick is to wedge a rag below the ring gear and then turn the gear (or pinion). This forces the rag to get sucked in where the ring gear and pinion gear teeth mesh and should help leverage the carrier out a little. Then follow up with the prybar.
	Once the carrier is loose finish pulling the side bearing caps and lift the carrier completely out of the housing. Be sure to keep each side carrier bearing race with it’s respective bearing since they’re matched.Move the carrier to a clean work surface. If you plan to re-install your old ring gear then mark it’s position on the carrier. It needs to be reinstalled the same way it came off. Once it’s marked unbolt the ring gear and set it aside.
	Now use a punch to tap out the roll pin holding in the pinion shaft (cross shaft). If you don’t have the right size punch an old drill bit makes a good substitute. Just be sure to use a brass or plastic dead blow hammer and definitely wear eye protection. Drill bits are hardened and a normal steel hammer can shatter them. (Photo shows roll pin already removed)
	Tap the pinion shaft (cross shaft) out of the carrier and the spider gears should fall right out. You can toss all 4 spider gears, but you need to re-use (or buy new) the thrust washers. These are the larger washers behind each side spider gear. (2 total)Now you’re left with the pinion shaft, thrust washers, and the carrier itself.
Examination of the parts:
	These are the parts you’ll use from your existing open carrier; pinion shaft, thrust washers, and the carrier itself. You should also buy a new roll pin to secure the pinion shaft in the carrier.The spider gears (side gears) inside the carrier will be discarded since the Aussie Locker replaces them.
	Check that the pinion shaft isn’t worn. Using a micrometer compare the diameter at the end of the shaft with a spot where the side gears ride. There should be no more than .002″ difference.
	Double check the hardness of the shaft by scratching it with a small file near the center. The file should slip off the surface, not leave a groove. If it leaves a groove then the shaft should be replaced.
	Examine your carrier for chips, cracks or other damage. If you find any you’ll need to get a new carrier. Here you can see one of the four cracks that I found when I removed my carrier. This was a disaster waiting to happen! Luckily I wasn’t going to reuse the carrier anyway since it’s a limited slip carrier and the Aussie Locker requires an open carrier.
	Check your thrust washers for wear and warping. When I first insalled the locker I couldn’t get the tolerances to meet specs (see next section). It turns out my original washers were warped. A quick trip to the Ford dealer got me two new ones. See the photo to the left comparing the new (left) and the old (right).
Checking Case Tolerances:
	In this step you’ll need to partially assemble the locker in the carrier/case to be sure the tolerances are within spec.First, place your carrier in a bench vice. Be sure to use plastic or rubber vice jaw inserts so you don’t damage the carrier. Open the Aussie Locker box and take out the Axle Gears and the Spacers.
	Coat the Axle Gear teeth, center opening and back with medium to heavy axle grease. This will help hold the parts together during assembly.
	Take your existing thrust washers and install one on the back side of each of the two Axle Gears.
	Install one Axle Gear with thrust washer into the carrier.
	Now the other side.
	Put a little grease on the back lip of the spacers and install one on each Axle Gear. The open end of the spacer goes toward the Axle Gear.
	Now carefully install the pinion shaft (cross shaft). Always use a plastic or brass hammer to avoid damaging the shaft. As the shaft starts to engage the spacers be sure they are completely pushed to each side so the shaft can pass between them.
	Tap the shaft completely into position. The ends of the shaft should be flush with the outside surface of the carrier.DO NOT install the roll pin at this time. The pinion shaft is coming back out for the next step.
	Using a screw driver pry one of the spacers away from the pinion shaft. Measure the gap (at the tightest spot) using a feeler guage. Repeat for the other side. The gap should be .006-.020″. This is a critical measurement and will affect how the locker functions. If it’s not within range you need to figure out why and correct it before proceeding.If the gaps are within range you can go on to the next step. Slide the pinion shaft back out using a brass punch. Also remove the Spacers, but leave the Axle Gears and thrust washers in the carrier.

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We’ve all had brake problems at one point or another, sometimes even the caliper is needing to be replaced. I’m going to show you how to rebuild one, to save the cost of a rebuilt unit. This is inexpensive, and pretty easy to do. Once you do one, the next one goes much faster.

For this article, I’m rebuilding the OEM calipers on my 76 Bronco. Tools: Air compressor, with blower nozzle Pick set Scotchbrite (or similar) pad Brake Cleaner Brake Fluid (Dot 3 in my case) Caliper Rebuild Kit (Autozone part # 66781) Big C-Clamp, or caliper compressor tool Safety Glasses Chemical Resistant Gloves

Safety first. Put on your safety glasses at all times when working in the shop, and use your chemical resistant gloves when using the brake cleaner.

Figure 1

The first thing is to remove the caliper from the vehicle, clean it up a little, and lay it out on your work surface (Figure 1)

Figure 2

Next, take your air hose, with blower nozzle, and in very short bursts, work the piston out of the caliper. It will make a loud ‘POP’ sound, and is startling, so be ready, and don’t drop the piston on the floor where it can get nicked. (Figure 2) It may be necessary to put some electrical tape on the nozzle of your blower, to let it make a little better seal on the brake line opening. If the rings are so blown out that the air hose trick won’t work, you can re-attach the caliper to the vehicle, and have a buddy slowly pump the brakes to push the piston out (this will make a very big mess, be ready).

Figure 3

When it comes out, it will look like this (Figure 3)

Figure 4

My seals weren’t really leaking, but I had the axle all apart for rebuild, and there was plenty of funk on the piston anyhow. (Figure 4)

Figure 5.1

Figure 5.2

Use your picks to carefully remove the old O-Ring from the caliper body (Figures 5.1 & 5.2)

Figure 6

I don’t have a parts washer at the Farm, so I use my oil change pan for a cleaning surface. I use the brake cleaner to get the first bit of crud off of the piston and caliper (Figure 6)

Figure 7

Figure 8

Scrub the inside of the caliper and the piston with the Scotchbrite pad, to remove any nicks and burrs, as well as any caked on old brake fluid (Figure 7 shows a clean piston, Figure 8 shows the crud inside the caliper body part way through cleaning) Now that it’s all clean, take the O-ring out of the kit package, coat it liberally with new brake fluid, and put it into the groove that you picked the old one out of in the caliper body.

Figure 9

Slide the dust boot onto the piston, there is a groove for it, and make sure that it seats down nicely. This picture is for illustrative purposes, to show the proper orientation of it, you’ll slide it down in the next step to star the re-assembly process. When you compress the piston back in, just be sure that the skirt of the dust boot settles into this groove (I coat the dust boot with a little brake fluid where it goes onto the piston and caliper to make it slide nicely) (Figure 9)

Figure 10

Coat the o-rings, all sealing surfaces of the dust boot, and the piston itself with liberal amounts of brake fluid. Slide the dust boot down to the bottom of the piston, and work the bottom lip of it into the groove for it in the piston (the ‘flat’ side goes toward the caliper body, the ‘open’ side faces out where the brake pads will mount) (Figure 10)

Figure 11

Next, use your big C-Clamp to gently compress the piston back into the caliper (Figure 11) Be sure it doesn’t get out of line, or try to go in at an angle, take your time, and it’ll go in smoothly. If you so choose, now is a good time to replace the bleeder screw with a new one. Clean up your mess, and voila! you’ve just rebuilt your first brake caliper. It’s now ready to be re-installed on your rig for many more years of reliable service. Tech article by Jason Rodgers (Gummi Bear)

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Tools needed

• A flat surface
• Masking tape
• 4 feet of string
• Chalk (for marking)
• Hydraulic jack with stands (if needed)

Simple five steps

• Park your rig on a flat surface.
• Tape one end of the string to the bottom (6 o’clock) of the rear drive shaft. Using a clock method to determine location, bottom would be 6 o’clock, and the top would be 12 o’clock.
• Mark the rear tire where it touches the ground.
• Now push your rig forward so that the tire make one full rotation
• Look at string on the drive shaft.

The string will wrap around the drive shaft and the amount of wrap it has will tell you roughly what gear ratio you got.Example:
If the string is wrapped around the drive shaft 3 ½ times than you have the 3.50 to 1 gear ratio, which came stock behind a 302 V8.
If you got the string wrapped around 4 ¼ times than it will most likely be 4.11 to 1 gear ratio.
If it is wrapped 4 ½ times than it will be 4.56 to 1.
If it is wrapped 4 ¾ times than it will be 4.88 to 1.

If you don’t have room to move the rig, here is another way to do it. Instead of pushing the rig just jack up on rear tire and rotate it one full turn with vehicle in neutral. Count the number of wraps and times it by 2. The total is what you use to figure the gear ratio. Note this procedure will only work with open diffs.

by Honorio Madriaga

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You want traction? Get locked. Both wheels locked together on the same axle, all four wheels locked to the transfer case = maximum traction. No wheel slip, no spin. Just relentless, crawl-over-boulders-the-size-of-Volkswagens-even-when-one-or-two-tires-are-dangling-two-feet-in-the-air traction. “How”, you ask?

Well, take your pick – you can weld the side gears to the carrier to prevent any axle rotation independent of the entire carrier itself (simple, cheap, and easy..but kinda permanent), bolt in a “lunchbox” locker that simply replaces the side and spider gears in your open or limited-slip carrier (in my experience, “limited-slip” diffs are usually more “slip” than “limited”), you can replace the carrier itself with a “sometimes” locker that is locked most of the time, but allows a little bit of wheel speed differentiation when cornering by ratcheting (and clunking, and banging, and popping that makes it sound like you’ve got a ring gear tooth or two broken off and flying around in the axle housing)…or, you can step up the user-selectable lockers-either air, cable, or electrically actuated.

Which one is right for you? It depends on lots of things-your vehicle, your driving style, the terrain you drive on, your budget, and how much you like lying in the mud underneath your truck at night on the trail replacing U-joints or axleshafts-or waiting for somebody to show up with a winch to drag you off the obstacle you’re stuck on.

If your rig is a daily driver, your significant other drives it now and then, or you just like having complete manual control over your drivetrain, selectable lockers are a great way to go. They aren’t cheap, but they are the ultimate in control. Turned “off”, or unlocked, the axles behave just like open diffs-all four wheels are entirely independent of each other, making parking, sharp corners, and towing a breeze. Turned “on”, or locked, all four wheels turn at the same speed, all the time, no matter what-at the flip of a switch of pull of a lever.

OX Lockers are mechanical lockers that replace the entire carrier in the axlehousings and use a cable-actuated shifter fork located in the cover to slide a locking ring sideways, engaging both axles and connecting them solidly together. The entire construction of the system is aerospace-grade quality – billet steel covers that are stronger than most skidplates, teflon-lined stainless steel cables, and massive, precise, beautifully machined carriers that are industrial works of art.

In this write-up, I’ll document the installation of OX Lockers and 4:56 gears into both a Dana 30 and a Dana 44 axle. They’re very similiar-the main difference being this particular Dana 30 front axle used a crush sleeve to set pinion bearing preload (the amount of torque required to turn the pinion shaft with the pinion nut tourqed to spec), while the Dana 44 used shims behind the inner bearing race in the housing to achieve the same result.

Let me take a moment here and give you something to think about. This is NOT an easy, bolt-on-in -a-couple-hours little upgrade..UH-UH. It’s a major undertaking, and it involves some pretty specialized tools, a lot of patience, and a LOT of time. I’m not trying to talk you out of doing it yourself, but it took my brother and I 4 DAYS to get everything taken care of-and while we’re not professional mechanics, we both have many, many years of experience working on all types of vehicles- from air-cooled VW’s and Porsches to front drive imports, to ’60’s, ’70’s, and ’80’s Detroit iron-not to mention a pretty well-equipped garage (even better eqippped, now). Granted, we wasted quite a bit of time running around town to parts places, machine shops (that were closed), and tool supply houses (I LOVE HARBOR FREIGHT!), and some more trying remove the old bearings without the proper tool (hydraulic press) – but, still..even if everything had gone perfectly it would have taken at least the better part of two days. Think hard about doing it yourself, or paying a Pro to do it..and choose wisely.

Here’s a list of the special tools you’re going to need in order to accomplish the install-along with the usual hand tools, floor jacks, jack stands, air compressor, impact wrench, etc:

• A hydraulic press -or at least have easy access to one. If you don’t, don’t bother even starting -you aren’t going to get very far. No, don’t be thinking a big gear puller or a vise and a BFH is going to work- ’cause it ain’t. Trust me.
• Make sure you have a BFH anyway-you might need it. (If you don’t know what it is, you don’t work on trucks much.)
• A bearing separator -the kind that wedges behind the bearing and allows you to apply force to the entire backside.
• A breaker bar -to torque the pinion nut while setting the pinion bearing preload.
• A die grinder – to open up the old bearing races so they can be used as setup bearings-or you can buy setup bearings and races when you purchase the lockers and gears. (Spend the money-you’ll be glad you did. Really.)
• A big (I mean BIG) prybar -(useful for removing the old carrier from the axlehousing, holding the driveshafts while you remove and torque the yoke nuts, and getting stuck under the creeper wheels constantly while you’re rolling around under your truck.)
• A dial indicator with a magnetic base -to measure the backlash of the gearsets.
• A precision caliper -to measure the bearing shims.
• A 250 ft-lb torque wrench.
• An inch-pound torque wrench -to measure the pinion preload.
• A couple spray cans of brake cleaner -to clean the axle housings (and brakes).
• 3 or 4 quarts of quality gear oil, a tube of Locktite, and some gear marking compound.
• Lots of rags, paper shop towels, and hand cleaner.
• A 3-day weekend -(if you think you’re going get all this done in just a few hours, you’re either an optimist, an idiot, or a mechanic on Walker Evan’s race truck.)

Take my advice here and plan for your rig to be out of service for at LEAST a few days and have other transportation arrangements set up. You’re probably going to need to run to the parts and/or hardware store at least once during the course of this project, and not having to rush things back together so you can get to work the next day really cuts down on the stress level, and keeps you from making mistakes and bad decisions at 2:30 in the morning. I know.

OK, you ready? Got everything lined up? Kiss the kids and wife goodbye for a while, take a deep breath, and jump right in. Park the truck on a clean, level surface. A garage floor is excellent-a sloping dirt driveway is bad. Of course, if you’ve got a hydraulic vehicle lift and a fully-equipped shop, that would be OK, too.

• Jack it up and place stout jackstands under the frame where they won’t be in your way as you’re crawling around underneath the truck for the next few days. (They will, of course-but you can try.)
• Remove wheels and tires and move them out of the way so you won’t be stumbling over them all the time.
• Place a drain pan under the diff housing and remove the cover-give the lube a while to drain, it’s pretty thick. Inspect it for contamination-if it’s foamy, milky, or has grit and dirt in it, it’d be a good idea to replace the axle tube seals during the course of the project. (See? I told you you’d be going to the parts store.) Also, think about lengthening the axle vent hoses.
• On a Dana front axle, remove the hub/rotor assemblies (or drums and backing plates, if so equipped) from the outer knuckles so you can pull the axleshafts out of the housing. On a Dana rear, remove the drum (these can be stubborn), and using the hole in the axle flange for access, unbolt the 4 nuts retaining the axle to the housing. If you’re lucky, it’ll slide right out after a good tug-if not, either bolt the wheel back on the axle and use it for leverage, or use a slide hammer to persuade the axle out of the housing.
• Check the carrier caps for markings so you can bolt them back the same way you take them out-if not marked already, use a punch to mark them clearly.
  

• Unbolt the caps, and using a large prybar and most of your impolite vocabulary, “gently” remove the carrier from the housing-watch it, it’s heavy. Don’t give yourself a hernia. Also, don’t drop the carrier on your toe.
  
• Unbolt the driveshaft from the pinion yoke and secure it up out of the way with a coat hanger or something. Now, grab a long piece of angle iron and drill two holes near one end that match two of the yoke bolt holes. Use two of the u-bolt strap bolts to secure the angle iron to the yoke and still leave room to get at the pinion nut-this will hold the yoke while you zap the nut off with an impact wrench. Alternatively, you can use a LARGE wrench to try hold the yoke-but it’s not easy.
• Tap the pinion shaft out of the housing, making sure to keep track of bearings, shims, seals, slingers, crush sleeves, etc so you can put it back together in the same order. If this is your first time in a differential, I can’t stress this enough!!
• Remove the old bearing races from the housings.
• Clean the housing thoroughly.

Now, you’re about halfway there. Stop and take five. Have a beer. Eat something. Feel better? OK, back to work.

If you bought “cheater” or “setup” bearings when you bought your new gears, good for you-you can skip this step. If not, read on. Use the bearing separator and press to remove the old bearings from the carrier and pinon shaft (those bearings are ON there-after breaking a 5-ton 3-jaw gear puller AND an A/C clutch puller, we gave in and bought a hydraulic press from Harbor Freight-good thing they were open on Sunday morning) . Carefully record the shim pack thickness for each bearing, and DON’T MIX THEM UP. Use a die grinder to remove just enough from the inner diameter of the bearings so they’ll just slip over the journals of the Locker carrier and new pinion shaft -and from the OUTER diameter of the old bearing races so they’ll just slip into the housings. You’ll appreciate this when you’re constantly installing them and removing them as you adjust shim thickness to get the correct backlash and gear pattern setup. Clean the old bearings well after you’re sure they’re a slip fit.

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The first thing you have to do is get some help. You already know that you will have to cut your front axle housing in half and the darned thing weighs more than most mortals can lift by themselves. I have chosen to use a band saw, to do the deed, since it will do a much better job than I could do with a sawzall. I will TIG or MIG weld whatever needs it. If a special tool is called for or a different technique is used other than the ones described in the instructions that came with the WAH kit, I will make a note saying so.

The first thing I did was remove the tie rod and drag link. Then I took the track bar off. Removing the nuts from the radius arms is important at this point because I jacked the bronco up and placed jack stands under the frame directly behind the radius arms to support the weight of the bronco while the transformation takes place. There is no room for a wrench at this point so that is why I did it ahead of time. This places most of the weight of the bronco directly on or slightly in front of the jack stands. Make sure that the vehicle is stable. As a precaution, I put some tension on the front bumper with my high lift jack; to be sure that the jack stands weren’t alone in their task. Next I removed the shocks and the coil springs as well as the front drive shaft and the rubber brake hose that is attached to the frame. Be sure to cap off the steel line coming down to the frame as well as the rubber line. Once these things were completed, the whole front assembly was rolled out from under the bronco and I placed it on jack stands.

At this time, the spring perches and radius arms were removed. The calipers and brake lines were taken off as one assembly and then the lock outs and hubs.

The spindles and caliper brackets were removed as well. I then took the axles out and removed the bolts from the front cover and drained the lube from the differential. Since I plan to take the housing to the car wash and clean it up really well on the inside and out, I decided to remove the carrier and pinion. This is not called for in the instructions, but rather something that I wanted to do.At this point, everything that needs to be removed is done and will be cleaned in a parts washer or washed at the local car wash, awaiting the WAH installation.

Cutting the housing is very easy and the instructions say to mark the tube 4 ½” from the passenger side differential housing and, using a pipe cutter, make a mark all the way around the axle tube.

I chose to use a band saw that is fairly precise and didn’t need to use the pipe cutter. If I had been doing this at home, my options would have been a sawzall or one of those little band saws they sell at Northern tools or Harbor freight.

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Several years ago, I installed a 2 ½” suspension lift on my mostly stock ‘70 Bronco. The lift turned out very well, and I was very pleased with myself. It completely changed the way my Bronco looked, and I was proud to drive it down the street. So proud, in fact, that I could completely ignore the newly created vibration in the suspension. For a while, anyway… For the last year however, that vibration has become more irritating, since by then, I was pretty sure what caused it. In my Bronco, the vibration started around 40 mph. and continued through 65 mph. or so, which is as fast as I ever seem to drive my Bronco.

The reason for the vibration was the increase in the pinion angle from installing the suspension lift. The term “pinion angle” is generally considered to be the difference, expressed in degrees, between the centerline of the pinion gear in the rear differential, and the centerline of the driveshaft. The increase in pinion angle is due to the suspension lift raising the frame and drivetrain, including the transfer case, and not the rear differential. Since the transfer case end of the driveshaft is now several inches higher, the angle between the driveshaft and the pinion gear is increased.

Normal, or stock pinion angle, is somewhere around 1-1 ½ °. As the pinion angle increases past 3-4°, the u-joint will experience increased wear and possible premature failure. As the pinion angle increases past 9-10°, the vibration I experienced will be felt, along with the increased wear on the u-joint.

Here’s a picture showing the rear yoke and driveshaft. You can see with your eyes how much of a difference there is.

So, now that I knew what the problem was, what were my options for fixing it. One option could be to remove the rear differential, cut off the spring perches, rotate the differential to obtain the proper pinion angle, and then re-weld the spring perches back on. But I wasn’t too happy with that option. That seemed like more work than necessary, and, I don’t own a welder.

Another option is to install some tapered shims between the leaf springs and the spring perches. This would wind up rotating the rear differential housing, and it’s a simple bolt-on. This seems like the best choice.

Now that I had decided on installing the shims, I needed to determine what angle shims to install. This would involve measuring the current pinion angle. I did search on Google for “measure pinion angle”, and had a listing of more technical articles that I could read in a lifetime.

There are two methods for measuring the pinion angle. The first method uses an angle measuring gauge (adjustable protractor) to measure the difference between the pinion flange and the drive shaft directly. These gauges are available for under $10 from a hardware store. Place the edge of the gauge vertically against the front of the pinion flange, beside the driveshaft. Extend the measuring arm forward parallel to the bottom of the driveshaft. Extend a straight edge under the driveshaft to the measuring arm of the angle gauge. Hold the straight edge flat against the bottom of the driveshaft and adjust the measuring arm to read the angle. Depending on the gauge you use, you may have to subtract 90° from your reading to get the correct number.

The second method measures the angle, from horizontal, of the driveshaft and pinion shaft separately, then comparing the two. You can use a gravity angle gauge (available at hardware stores) to do the measuring. I happened to already have a machinists level, which seemed to work just fine.

My first step was to measure the angle of the driveshaft. Just lay the angle finder or, in my case, the level, along the length of the driveshaft. Adjust the angle until the bubble is centered, then note the angle. For me, the angle was 18 ½° from horizontal.

Next, measure the pinion gear centerline angle. Since you can’t really get to the pinion gear shaft, the acceptable thing to do is to measure the angle of something at 90° from the pinion shaft, and add (or subtract) 90° from that reading. I chose to measure across the face of the yoke, so I removed the two u-joint u-bolts and moved the driveshaft out of the way. Then placed the level across the face of the yoke, and took my measurement. This turned out to be 8°. So, the difference between the driveshaft angle and the pinion shaft angle is 10 ½°. Looks like I need some correction!

When determining what degree shims to buy, remember that installing shims rotates the differential, which will raise the yoke relative to the transfer case. This changes the driveshaft angle, which ultimately reduces the pinion angle. I wanted to wind up with about 2° of pinion angle when I was done. With my current 10 ½° pinion angle, I would have been inclined to order 8° shims. But, after thinking about the yoke moving up, lessening the driveshaft angle, I decided to order 6° shims.

In doing some research on installing rear axle shims, I constantly came across recommendations to NOT use aluminum shims, especially cast aluminum. It seems they have a tendency to deform over time, and, on occasion, crack and fall out. This leaves the rear differential loose on the springs. I ran across a company in California, 4Crawler Offroad, that custom makes several items for off-road vehicles, including steel axle shims. I can’t say enough good things about 4Crawler Offroad and their web site. Not only do they offer quality products for sale, but, as an example, in the section on shims, provides and explanation of the shims and what they do, how to measure for shims, how to install shims, FAQ, etc. If you can’t tell, this company impressed me. Find them at http://www.4crawler.com/4×4/ForSale/Shims.shtml.

The shims I ordered were a stock size, 4 ¼” by 2 ½” by 6°. I placed the order through the web site and had the shims in just a couple days. Here’s a picture of the received shims.

Now that I’ve got the shims, I need to install them. First step is to jack up the Bronco and support it by the frame, then remove the wheels to aid access to the axle u-bolts. Here’s a picture of how I manage to get a little extra height out of my 4 ton jack stands.

Support one side of the differential with a floor jack. Although the pictures don’t show it, my jack is under the brake drum. Remove one end of the shock so it doesn’t limit the droop of the differential when you remove the u-bolts. I’m still running the stock rear shock mounts, and it was easier to remove the top of the shock. Some type of penetrating oil is always a good idea on these types of projects.

Remove the u-bolts and spring retainer. Position a c-clamp on each end of the lower leaf and tighten, to hold the spring pack together when removing the leaf spring bolt.

Lower this end of the differential, and use whatever type of persuasion is necessary, until the leaf spring bolt comes loose from the spring perch. Remove the leaf spring bolt. Here’s a picture of the removed leaf spring bolt, for anyone who hasn’t seen one before. Note the round head to fit the hole in the spring perch.

My 6° shims are about ¼” thick where the spring bolt goes through. I got lucky and had an extra ¼” of thread left on my spring bolt. If you don’t have enough bolt thread left, you will have to buy new, longer spring bolts. Measure the original bolt carefully, as the replacement spring bolts come in different size heads, as well as lengths. Insert the spring bolt through the correct side of the shim, slide back through the spring pack, and tighten up the nut. These shims are made with a relief on one side so the spring bolt head has a surface that’s parallel to the spring. This way the spring bolt head won’t get cocked to one side as it’s tightened.

Jack up the differential, making sure the spring bolt head gets fully inserted into the spring perch. Reassembly is pretty much the opposite of disassembly. Finish up one side, then on to the other side. Total time to install the shims, from jacking up the Bronco to cleaning and putting away my tools was only 3 hours, including time to take pictures. Here’s a picture of the installed shim.

I got everything back together and took a final measurement of the pinion angle. I was happy to find that I wound up with a 2° pinion angle. Of course I had to take it for a ride and was amazed to find how smooth it drove. All the vibrations I’d been living with for the past several years was gone. This project was a big success!!!

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