YUKON SUPER JOINT - U-Joint INSTALL HOW-TO

By Lou Dawson

Our Willys flatfender, known as Rumble Bee, needed stouter front axle shafts and U-joints, so we installed alloy shafts and Yukon Super Joints.

Our yellow flatfender is wedged in the Billings Canyon, Colorado gatekeeper obstacle -- jammed so tight you can imagine it grew there. It's our first trail of the season, I'm a tad heavy on the go-pedal when I should be using our shiny new winch. Snap. Was that a U-joint I just heard grenading?

The repair isn't too bad, involving a trip down to the local NAPA store for a new U-joint, and a bit of grunt to pull the tweaked axle-shaft yoke out of the steering knuckle. But do I really want to do this again? Carnage is fun, but it's more fun when it doesn't melt your credit card (we needed a new axle shaft as well as U-joint).

Yep, time for an upgrade: Alloy axle shafts that my low geared V-6 can't twist into pretzels, and Yukon Super Joint U-joints, the incredibly beefy units that eliminate pesky needle bearings, use full circle snap rings, and could generally be considered "unbreakable" for a lighter weight application such as Rumble Bee.

Yukon Super Joint and alloy axle.

Like any longtime Jeeper I've changed out my share of U-joints, but Chris Overacker of CODE 4x4 warned me that the Super Joint was a bit tricky, and that as a first timer I should install them under his watch. He was right.

Follow along as we do the upgrade. If you need Super Joints for yourself, contact CODE 4x4 to take advantage of their expertise and tooling (hint, doing this job with a press is WAY better than bashing your bearing caps with a hammer -- especially Super Joints, as they go in tight!).

Prep those bores!

1. Preparation. Check for burrs in the axle shaft bores that hold the U-joint bearing caps. Smooth with a fine round file and emery cloth. If you're re-using shafts, inspect for proper dimensions as the yoke ears can be bent when you're pressing out the U-joint caps (or when you get caught in the boulders and break something). Exact yoke dimensions are in the directions that come with the Super Joint, or just put snap rings and caps on a U-joint, then hold it against the outside of the ears and eyeball for proper dimension that will allow the snap rings to fit between the ears of the yoke. If your yoke ears are bent, carefully correct using a vise or press. Surgically clean the bearing surfaces of the Super Joint, as without space between needle bearings there is no room for dirt particles. Sort all the small parts (springs, grease pistons, etc.) into some containers such as jar lids.

Organize everything before you start.

Install O-rings on grease pistons as shown here.

2. Pre-assembly. Install the big O-rings in the groove inside the bearing caps, and ease the little O-rings over the brass grease pistons so they fit in the obvious groove. Take care not to loose the smaller O-rings as you work them over the pistons -- drop one and it'll bounce away never to be seen again.

3. Prelube. Use the special grease that comes with the Super Joint. Smear a thin layer around the inside of all the bearing caps.

4. Install cross in yoke. If you're using full-circle snap rings, place them on the cross before you install in the yoke (standard snap rings can be installed later). Inserting the cross in the yoke is tricky but you eventually get the hang of it.

Inserting cross in yoke, upper arrow points to groove that allows the cross to move into position, lower arrow points to end with chamfer for same purpose. Snap rings are missing for demonstration purpose.

Notice there is a half-groove on one side of the cross, and an angled chamfer out on the end on the opposite side. Insert the cross in the yoke so the groove is oriented away from the axle -- if you do it correctly, it'll be obvious that the groove and chamfer are designed to allow the oversized cross to completely enter the yoke. With snap rings on the cross you may need a small amount of persuasion with a plastic mallet, but it should obviously move as if designed to do so.

Starting a bearing cap. A press works best. Note snap ring.	Don't forget the grease spring and piston, shown with arrow.

5. Install caps. Grease a spring and piston, insert both into bore on the end of the cross. We preferred to do these one-at-a-time as we installed the caps, but DON'T FORGET these small parts, since pressing the cross and cap back out of the yoke to correct a mistake is a rather involved process (CODE has all the tricks for un-installing Super Joints, contact them to have this job done professionally).

CODE 4x4 has the perfect press for this type of work.

Get the cap started by placing axle shaft in vise, then tapping the cap in a short distance with a large brass punch. Orient the cross in such a way as the grease piston can't fall out of the bore while you're working. Once the cap is started, move to the press and finish the job.

Take care not to over-insert the cap -- stop when you first see the snap ring groove and try installing the snap ring; continue to press carefully if you need more clearance. If you don't have a press you can pound the cap in -- but do so with care.

The full circle snap rings may be tricky to install. Use good quality large-size snap ring pliers, and try rotating the snap ring so a narrower part of the ring allows it to clear obstruction possibly caused by the side of the land machined on the inside of the yoke. Repeat process for all caps. It helps to have an assistant while installing the second part of the axle shaft.

Working the snap ring into place.

6. Set snap rings. Check the seating of the snap rings by manipulating with a small screwdriver. Firmly strike the ends of the yoke with a hammer, which causes the bearing caps to move to their final position, thus allowing the snap rings to fully seat. Double check.

7. Install zerk grease fittings. If your Super Joints take threaded zerks that protrude above the surface of the cap, install these AFTER installing axle shafts in housing, as the hole in your steering knuckle may not have enough clearance for the zerks. Some version of the Super Joint may be sold with press-fit zerks that flush mount, in that case install on the bench.

Another view of install, note snap-ring ready to go, and groove on outside of U-joint that allows insertion into axle yoke.

8. Lubricate. Place special grease (comes with Super Joint) in the needle tipped grease gun that comes with the Super Joints. Pump several times to purge air, then pump grease into all 4 zerks on top of the bearing caps. DO NOT pump till grease comes out of the bottom of the cap (as you would with normal U-joints), instead, simply pump until you feel an increase in the effort it takes to squeeze the gun handle. The idea here is that you've loaded enough grease in the Super Joint bore to compress the spring and grease piston, thus creating e a reservoir of pressurized grease inside the cap. Greasing with too much force will blow the O-ring seal inside the cap, and you'll end up without the pressurized reservoir necessary for the proper function of the Super Joint. Yukon recommends greasing 4 times a year for average vehicle use.

The completed units are a thing of beauty -- and strength!

(Author Lou Dawson is our CODE4x4 webmaster and a well known Colorado outdoor writer who's first drive was his dad's flatfender Jeep. Article copyright Louis Dawson, WildSnow.com )