- Sep 20, 2006
Autoblog Project Garage: Axle swap, Part II
With the axle disassembled in the previous installment of this project, it is now time to start putting things back together with fresh parts as needed.
One surprise that we encountered during the tear-down of the axle was a significant amount of debris; namely, there was a lot of dirt inside the axle. Yet, the internals were in good shape, so we do not believe that the axle was operated with contamination. Our guess is that either it came from a flood car (not exactly a stretch, considering last year's events), or was submerged at some point during the salvage process.
Components small enough to fit in a 5-gallon dip tank, such as the differential carrier, were cleaned by soaking in solvents. Other parts were sprayed with brake cleaner (which tends to be the default choice for general parts cleaning due to its effectiveness and cost).
To clean out the inside of the axle, we ran several solvent-soaked rags through each axle tube, and thoroughly cleaned out the center section of the housing with particular care paid to the pinion bearing lubrication channels.
We highly recommend the use of solvent-proof gloves when working with such chemicals, and of course don't forget to wear eye protection.
The old differential carrier bearings were removed with a two-jaw puller, and new bearings were installed via the use of a press.
When pressing on a bearing, make sure that it is seated fully - often, the bearing needs to be driven so that it is below flush with the mating component. In this case, we used the outer race from an old wheel bearing to fully seat the carrier bearing.
The rotors that came with the axle were still thick enough to be usable, so we had them turned on a brake lathe at the local NAPA. They started rusting almost immediately, of course.
To clean up the appearance of the axle housing, we started by using a wire brush to remove any loose rust (there was no paint to remove, as it appears to have received none at the factory). Then, Rust-Oleum's Rust Reformer was utilized to convert the remaining surface rust to a "paintable surface" with an appearance somewhat like black oxide. We have no idea how this stuff works, so any insight would be appreciated. We then laid down some primer and Rust-Oleum gloss black paint.
Get back to us in a year or two to see if this finish holds up to Michigan winters. We have our doubts.
A puller was fabricated to remove the old axle bushings...
...and new bushings were installed into the housing.
The tool consists of a yoke that we welded from some scraps of steel, and a punch that was turned on a lathe to a diameter about 0.060" smaller than the bushing. We found that the ID of the factory bushings is 12mm (not 1/2" like the aftermarket polyurethane bushing that we used to create the tool), and so we had to use 7/16" threaded rod (metric threaded rod not being readily available in our area). That material is marginal at best for the torque and axial loads generated during this process.
The next step was to install a new pinion seal (actually, that wasn't the next step - keep reading).
Since these axles are known for leaking around the outside of the seal, we've learned to install these seals with a light film of anaerobic sealer around the perimeter of the seal.
New axle bearings are installed into the ends of the housing using a brass punch. A soft steel punch can also be used, but be careful not to dent the outer race on this type of bearing.
We also used a punch on the axle seals, but a much better choice is a properly-sized seal installer since these seals are very easy to damage. We highly recommend that our readers use the right tool for this task.
We had that general feeling of "gee, it seems like we're forgetting something" when installing the first pinion seal, and of course that's because the front pinion bearing needed to be installed before the seal goes into place. That's a great reason why one should stop at the first sign of fatigue or distraction. We were fortunate enough that this mistake only cost $5 and a few minutes of time.
This time around, we squirted a bit of gear lube into the front bearing and dropped into place before pounding in a fresh seal.
A bit of gear lube was applied to the lip of the seal, and the freshly painted pinion yoke was then set into place.
The crush sleeve establishes the space between the front and rear pinion bearings, and needs to be collapsed to the correct height to set the bearing preload. A new crush sleeve (on the right, shown next to the collapsed part that came from the old assembly) is selected...
...and then set into place on the pinion. In case you're wondering, we didn't change out the pinion bearings, as they looked just fine.
The pinion is installed into the housing, some gear lube is applied to the threads, and a new pinion nut is started and snugged down with hand tools.
An impact wrench is then used to generate the 300+ ft. lbs. of torque required to start collapsing the crush sleeve. Not shown here is the large adjustable wrench we used to hold the yoke in place during this process.
Go ahead and try to use a cheater bar to tighten the pinion nut, but we've never had luck with anything less than a healthy impact wrench.
Once the sleeve starts to collapse, it's important to start watching the socket and check the bearing preload as the pinion nut is tightened. We check the preload every 1/16th turn once the play in the assembly is taken up.
The manual specifies a torque of 12 inch-pounds for the bearing preload. For those without a torque wrench that reads that low, it's basically just slightly tighter than zero lash. Don't overtighten the nut, as too much preload will wipe out the bearings due to lack of lubrication.
It is extremely important to use a new crush sleeve and pinion nut whenever the pinion is removed, as it will be difficult (if not impossible) to get the bearing preload set correctly with enough torque applied to the nut to keep it from loosening. If the nut is tightened too far, the pinion will need to be removed and re-installed with a new sleeve and nut.
New bearing races are installed onto the carrier. Never mix-and-match bearing and race sets.
The carrier is then set into place, and the shims installed back into the side from which they came. A bit of force may be needed to drive them back into place, but don't get too aggressive or the cast-iron shim may shatter.
Install the bearing caps (once again ensuring that they go back into their original location) and tighten them to the correct spec.At this point, it's a good idea to check the gear lash to make sure that it's still within spec (better yet is to measure it before disassembly, record the value, and hit it upon reassembly). In this case, we know that we can get away with changing out the carrier bearings without appreciably changing the lash, but this doesn't mean that everyone can get away with doing the same thing.
In our next installment, we'll finish up the assembly, and eventually we'll get around to actually performing the swap.