Gear Swap, Axle Gears, Driveshaft Gears, and Swapping Gears Guide

You've read it before, even in this magazine: Axle gear swaps are best left to a professional. This is wise advice, and for a lot of people, it's true. But if you're a hopeless 4x4 addict and a hard-core gearhead, the thought has no doubt crossed your mind to attempt a gear swap yourself. How hard can it be...it's just two gears, right?

Wrong. There's a heck of a lot more to it than a couple of gears, and getting it right is a heck of a lot harder than it looks. Even so, the thought of performing a gear swap at home had been kicking around in our heads for a few years and recently we grew the cajones to try it. We took an '88 Toyota truck that was hopelessly bogged down with stock gears and 33s, did some research, and then called Randy's Ring & Pinion Service. The crew at Randy's is very friendly toward the do-it-yourselfer, and each gearset comes with a booklet based on their years of experience that is vital for a first-timer. Read it, memorize it, and treat it as the gospel for gears.

What follows is a chronicle of our experience with loads of tips, tricks, and shortcuts for the do-it-yourself gear-swapper. We had never done a gear swap before and we did it at home, so you'll see a beginner's first-hand experience and not the typical look-over-the-professional's-shoulder type of thing. Also keep in mind the two axles used in this article are very similar to other types, and most of the tips seen here apply to any axle.

So were we successful? We've put almost 1,000 miles on the truck at the time of this writing with absolutely no trouble and, astonishingly, no gear noise. Maybe we got lucky or maybe we got it right. You be the judge.

1 We ordered 4.88 gears from Randy's Ring & Pinion service along with complete installation kits. In addition to the hard parts, the installation kits include a selection of shims, gear-marking compound, and everything else required for installation. Since we were going through all the trouble of changing gears, we decided to add some traction at the same time with a Detroit Locker for the rear and a Truetrac limited-slip for the front.
1 We ordered 4.88 gears from Randy's Ring & Pinion service along with complete installatio
2 It's just plain stupid to invest money in gears and installation kits and then try to install them without the necessary tools. Fortunately, Randy's has a selection of tools at reasonable prices. The minimum of what you will need is a set of calipers, a dial indicator to check backlash (both shown), a foot-pound torque wrench, and an inch-pound torque wrench. You will also need a shop press. We didn't have one, so we purchased an inexpensive 12-ton unit from Harbor Freight.
2 It's just plain stupid to invest money in gears and installation kits and then try to in
3 We're not going to spend a lot of time showing the steps required to get the necessary housing components out of the vehicle (such as the third member for the rear) because, frankly, if you can't figure that out, you don't need to be messing with a gear swap. On the rear it's a good idea to replace the outer axle bearings (not included with the installation kits) on high-mileage trucks. The front requires removing the differential housing completely, which can be done without removing the CV shafts with some finesse and a prybar.
3 We're not going to spend a lot of time showing the steps required to get the necessary h

4 A Toyota live axle has a drop-out centersection, or third member, that contains the entire ring-and-pinion assembly. This design is very similar to a Ford 9-inch and makes gear swapping easy because the whole operation can be done on a bench. They also use threaded side-bearing adjusters (arrow), which eliminate the need for separate carrier shims. The first step is to remove the lock tabs for the adjusters as shown.
4 A Toyota live axle has a drop-out centersection, or third member, that contains the enti
5 After marking the carrier bearing caps so you will be able to install them in the same position as they were removed, remove the bearing cap bolts and pull the adjusters, caps, bearing races, and carrier out together. Marking the caps is important because they are side-specific and machined to a precise tolerance; mix them up and you risk messing up the centersection.
5 After marking the carrier bearing caps so you will be able to install them in the same p
6 Next, it's time to remove the pinion nut. In order to do this, you need something to hold the companion flange so the pinion won't spin. We drilled a piece of angle iron (arrow) to match the holes in the companion flange and simply locked it against the workbench. This homemade tool is also essential for installation. The pinion nut takes a 36mm socket, and it will take some effort to loosen it because the nut was staked after installation.
6 Next, it's time to remove the pinion nut. In order to do this, you need something to hol

7 There's a bit of a press fit on the pinion bearings, so it may take a few whacks with a plastic hammer to remove the pinion from the housing. If it proves stubborn, an air hammer and a punch bit can usually make the pinion see things your way. If that doesn't work, it's likely that a bearing froze and friction-welded itself to the pinion, in which case it's time to break out the torch and find someone who is really good at using it.
7 There's a bit of a press fit on the pinion bearings, so it may take a few whacks with a
8 Unless you plan to reuse the bearings (which is stupid unless the truck has very few miles on it), the next step is to drive the pinion bearing races out of the housing. A long punch and a hammer are all you need, and there are access slots in the housing behind the races to make this a simple operation. Be careful not to gall any machined surfaces inside the housing. Now that the housing is completely empty, wash it thoroughly.
8 Unless you plan to reuse the bearings (which is stupid unless the truck has very few mil
9 If you are reusing the factory carrier, the next step is to free it from the offending ring gear. Even if you are using a new carrier, as we were, you'll need the ring gear bolts. Toyotas use lock plates on the ring gear bolts, so they will have to be flattened with a punch prior to removing the bolts. Install the new components using the bolts, torque them to 57 lb-ft in a star pattern, and restake the lock plates. Using Loctite isn't necessary because of the lock plates, but it doesn't hurt either.
9 If you are reusing the factory carrier, the next step is to free it from the offending r

10 Next, press the new bearings on the carrier. We've seen guys hammer bearings on with success, but it's hard to guarantee they will seat properly. It's a really good idea to have a selection of short lengths of tubing on hand to aid pressing the bearings on without damaging them. In a pinch, you can wallow out the inside of the old bearings with a die grinder (to relieve the press-fit) and use them to guide the new bearings in place. This isn't rocket science--just press the bearing on until the shop press starts to bind. Any more and you risk shooting stuff across the garage.10 Next, press the new bearings on the carrier. We've seen guys hammer bearings on with success, but it's hard to guarantee they will seat properly. It's a really good idea to have a selection of short lengths of tubing on hand to aid pressing the bearings on without damaging them. In a pinch, you can wallow out the inside of the old bearings with a die grinder (to relieve the press-fit) and use them to guide the new bearings in place. This isn't rocket science--just press the bearing on until the shop press starts to bind. Any more and you risk shooting stuff across the garage.
10 Next, press the new bearings on the carrier. We've seen guys hammer bearings on with su
11 Most experts say that using shims with the same thickness as original will set the new gears up correctly about 60 percent of the time. At the very least, the old setup will get you in the ballpark. The pinion is shimmed under the main bearing on Toyotas, which has a stout press-fit. Since we were fresh out of a bearing puller and we were determined not to guess at the shims' thickness, we broke out the cutoff wheel and cut the bearing off the pinion. The trick is to cut as deep a groove in the bearing as possible without hitting the pinion, then knock the fire out of it with a chisel to split the bearing and relieve the press fit. It worked...sorta. More on this later.
11 Most experts say that using shims with the same thickness as original will set the new
12 Measure the original pinion shims with the dial calipers--this is the exact thickness you will want to start with on the new gears. If you are starting with an empty housing and the shims from the original gears are unavailable, consult an expert on a good place to start, as every type of rearend is different and some are more sensitive than others.
12 Measure the original pinion shims with the dial calipers--this is the exact thickness y

13 Place the shims behind the head of the pinion, then press on the new bearing with the narrow end of the taper facing away from the pinion head. As we mentioned earlier, this is a stout press-fit, so coat the pinion with a liberal amount of WD-40 prior to pressing the bearing in place.
13 Place the shims behind the head of the pinion, then press on the new bearing with the n
14 Next comes driving the new bearing races into the housing. A set of bearing drivers makes this really easy, but has anyone priced a nice set lately? The poor man's alternative is a $12 brass drift and a hammer, which does an adequate job of seating the races without damaging them. However, because you can't put even pressure on the race as you drive it into place, you need to make triple-sure the races are fully seated. Here's a good gauge to follow: If you can get a fingernail behind the race, it isn't in there far enough.
14 Next comes driving the new bearing races into the housing. A set of bearing drivers mak
15 Pinion depth is what you should worry about first, and without a pinion depth tool the only way to find out if it's right is to perform a trial fit and check the pattern. Per Randy's recommendations, you should install the pinion without the crush collar and seal (we accidentally installed the new seal--oops) but with the companion flange and old nut, then tighten the nut until the pinion drag matches the final spec (8 in-lb in this case). This will give you an accurate setting without ruining the crush collar, which is one-time-use only. If you're lucky enough to get it right the first time you'll still have to take everything back apart, but the idea here is to hope for the best and prepare for the worst.
15 Pinion depth is what you should worry about first, and without a pinion depth tool the

16 With the pinion in place, install the carrier assembly, races, adjusters, and bearing caps in the housing. Make sure that the bearing caps are installed correctly (follow the marks made during disassembly) and that the adjusters aren't cross-threaded (it's not as easy as you'd think). The side bearing adjusters can be, well, adjusted with a punch, but it's easier to spring for a spanner tool (arrow). Run the adjuster closest to the pinion all the way in to seat the bearings, then back it off and slowly thread in the adjuster on the ring gear side to bring the ring gear close to the pinion.
16 With the pinion in place, install the carrier assembly, races, adjusters, and bearing c
17 Now you need to set backlash. This is the amount of slack or play between the ring and the pinion gears measured in thousandths of an inch. This is where a dial indicator comes in. Mount the magnetic base on the housing, then set the dial so that it engages a tooth on the ring. Lock the pinion in place (we wrapped a rag around the companion flange several times and held it tightly) and rock the ring gear back and forth to take a measurement. There is usually a small acceptable range (0.005-0.007 inch in this case) for backlash, but it's important to get it right for an accurate pattern.
17 Now you need to set backlash. This is the amount of slack or play between the ring and
18 All this work culminates in one crucial moment: reading the pattern. It involves painting five or six teeth on the ring and then running them back and forth across the pinion under tension. The pinion contact wipes away some of the paint so that you can "see" the tooth contact. Fortunately Randy's booklet offers several dozen illustrations of acceptable and unacceptable patterns for the unenlightened with recommendations on what to adjust if the patterns don't look good. In our case, the pattern indicated that the pinion was too far away, so everything had to come back apart.
18 All this work culminates in one crucial moment: reading the pattern. It involves painti

19 Remember when we mentioned the pinion is shimmed behind a pressed-on bearing and we cut the bearing off the old pinion because we didn't have a puller? We gambled that the gears would set up right the first time and lost. A trip to the tool store and $40 netted this slick two-jaw bearing puller so we could change shims.
19 Remember when we mentioned the pinion is shimmed behind a pressed-on bearing and we cut
20 Finally, three tries and quite a bit of frustration later, we obtained an acceptable pattern. A good pattern should have contact in the middle of the coast and drive sides of the ring gear teeth. Although difficult to see here, ours was a little high on the teeth but perfectly centered from heel to toe. We decided to let it fly and fortunately everything worked out. This is where patience really comes into play--you must be willing to take everything apart as many times as necessary to get the pattern right.
20 Finally, three tries and quite a bit of frustration later, we obtained an acceptable pa
21 After disassembling the centersection and installing the crush collar on the pinion, we attached our homemade companion flange holder and carefully tightened the pinion nut. This is tricky because if you go too far, you have to start over with a new crush collar. Once the slack is taken out of the pinion bearings, the drag on the pinion increases very quickly. The goal on this setup is only 8-12 in-lb of drag, so tighten just a little at a time. Fortunately Toyota crush collars crush fairly easily; be ready to break out the 3/4-inch drive sockets and cheater bars to crush the collars in GM axles.
21 After disassembling the centersection and installing the crush collar on the pinion, we

22 The very last step is to stake the pinion nut, which involves deforming it into a recess on the end of the pinion. An expert we consulted prior to the installation cautioned that Toyota pinion nuts are notorious for backing off and highly recommended using Loctite as well, so we followed his advice.
22 The very last step is to stake the pinion nut, which involves deforming it into a reces
23 Since the technical setup is identical, we'll hit the highlights of what is different on a Toyota IFS frontend. After wrestling the differential out of the vehicle, we discovered the axleshafts don't just slide out like the rearend. Plus, the service manual was calling for a special tool. With visions of making yet another trip to the parts store to rent a slide hammer, we popped off the diff cover to see if there was any way around needing another tool. Sure enough, we were able to pop the axleshafts out by carefully using a prybar against the cross shaft and the axle ends.
23 Since the technical setup is identical, we'll hit the highlights of what is different o
24 Unlike the rear, the frontend does not use threaded adjusters. Instead, it uses shims placed on the outside of the carrier bearings similar to a GM 10- or 12-bolt axle. Therefore, the carrier has a press-fit in the housing. A case spreader is handy to relieve the tight fit, but two prybars above and below the axle centerline in this manner can be used to pull the carrier out. Be sure to mark the shims to match the original setup with the new gears.
24 Unlike the rear, the frontend does not use threaded adjusters. Instead, it uses shims p

25 Assembly of all the new components for the front is identical to the rearend. Once the pinion is installed, the carrier goes back in the housing with the shims on the outside of the side bearings. It's a tight fit, and we had a heck of a time getting the carrier back in on the bench. Then it dawned on us to let gravity help and we set the housing vertically on the floor. Once in position as shown, it took some light persuading from a plastic dead-blow hammer to seat the carrier in the housing without damaging it.
25 Assembly of all the new components for the front is identical to the rearend. Once the
26 Other than what was noted, the setup for the front differential was the same as the rear. Believe it or not, the gears for the front set up properly the first time! This is where keeping track of the original shims and using quality components really pay off. The multitude of helpful hints from Randy's booklet didn't hurt either.
26 Other than what was noted, the setup for the front differential was the same as the rea

Are You Worthy?
We're all for diving into a project in order to learn something (we sure did in this case). However, we should issue a word of caution before you dive neck-deep into a fairly technical project such as this one. First, you need to take a close look at your toolbox and experience. You need a better-than-average complement of handtools, and having air tools makes things faster and easier. More importantly, we'd strongly recommend having some previous experience with big projects, such as rebuilding an engine or a transfer case, as well as some experience with axle work. It's also a big help to observe or assist in a gear installation with someone who has some experience prior to tackling your own project. Above all, you need to be confident in your capabilities. Although doing the labor on a gear installation saves a bunch of money, remember that you'll be out a wad of cash in parts if you get it wrong. Lastly, we can't stress enough the helpfulness of the booklet Randy's provides with all Yukon gearsets. We wouldn't have succeeded without it.