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Old 09-21-2008, 08:10 PM
ClarkGriswald's Avatar
ClarkGriswald ClarkGriswald is offline
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Join Date: Aug 2008
Location: Bloomingdale, MI
Posts: 256
How to Change/Lube Driveshaft U-Joint

Hello, in rehabbing my old bike I found myself wondering about the universal joint in the driveshaft. It's peace of mind to know what shape everything is in.


First thing I did was to open up the rubber boot between the middle drive and the swingarm, and used a piece of wood in the spokes of the rear tire (bike on centerstand) to hold it still while I removed the 4 bolts holding the U-joint to the middle drive flange. They are on there pretty tight so prepare to grunt.

With that out of the way you can remove the rear wheel, final drive assembly, rear shocks and swingarm.

The driveshaft will pull right out as has been covered in many threads (needs a healthy pull with some pliers with couple layers of paper towel or a rag in the jaws.. or a slide hammer if ya have one)..

Now you have the u-joint in your hands, and this is where the adventure begins............... (Your vision blurs..... you hear the sound of tiny bells ringing somewhere in the distance. Suddenly you realize your in another world!! ) Ok seriously now....

The pictures tell the story so I'll just add some tips and things Ive picked up over the years.

Here she is...


Not the biggest one in the world and it is also not lube-able in the normal sense. The cross on this one does not have passages for grease to pass thru the 4 ends, rather the hole you see only goes in so far. A grease zerk like you often see on automotive u-joints wouldn't help here because they are all closed. You would have to have grease fittings in all four caps and they would no doubt have to be the type that use a "needle tip" of a grease gun or a chainsaw tip greaser because I doubt a normal zerk would ever make it sticking out of a cap (no clearance). One more thing, on this setup, the yoke that hooks to the middle drive has an angled side to it. This makes it more difficult because a normal socket will not fit on there and line up easily.. More on that later.

The job can be done with a vice or even a strong C clamp. In my case I have a balljoint press kit for 4 wheel drive axles, it is basically a big C clamp. On cars/trucks I clamp this thing into a vice and use an air impact to run the screw in and out although only in small amounts because its not so much the pressure that free's up a stuck ujoint, it's a little pressure and just the right tapping/rap with a hammer combined with some penetrant. Or you can and probably will bend the yolk ear, be gentle.

Usually on cars I can just use the big clamp cause the hole is big enough and so is the male end, I don't need adapters. In this case the u-joint is much smaller and I had to use sockets to do the same thing, this is also how you would do it in a vise. I decided to go with my big clamp because I could sit at a desk and do it at night in my house.

Ok, on with it.

Here you see the u-joint with the 'C' clips removed and the clamp. When everything is right, you should be able to move the C clips around in a circle with a screwdriver, and with a little more force get 'em up and out of the groove, ya might need to use a screwdriver and a hammer to get 'em moving. The clips on this u-joint are pretty tough looking in my experience, most automotive ones Ive seen are pretty lame and break really easy. (plus most are rusty and rotten because they are not protected by a rubber boot). Also note that I have marked the yolks with a blue paint pen, this will let me keep them lined up the same way when it goes back together, I will replace the paint lines with some scratches with a file later.



Now time to take it apart. Hopefully you have sprayed it a few times with penetrating fluid by now, it helps. I will admit right now this can be a pain if you're not so good with your hands. If you have a helper this could be much easier, one person can run the vice or clamp and the other could help hold it all in place until you get tension on it..

As you can see here I am using sockets, one that is smaller than the bearing cap of the Ujoint and one that is larger that will recieve the opposite cap. Just use your best judgement because there are many sizes of u-joints but in our application they are smaller so you won't need any real big ones. The black metal piece you see is part of my ball joint kit, its just a flat part that keeps the socket from falling thru the hole, it's made for bigger stuff.




Be carefull now, too much pressure will only bend the yoke itself and then you have problems. Only apply enough pressure to make it tight, then use a hammer and tap around the "strap" or the hole that the bearing cap is in. Usually you will see and hear it pop loose and move.. if ya miss it and it falls apart in your hands thats ok don't get mad.. put it together again and keep pushing and tapping until you get all the way over and one cap falls out (into the big socket or at least is loose).



Here you see the first cap pushed out and the cross is over to the left.. now to go back the other way.. to be carefull/gentle with it you should engage the other cap back into its hole (in reverse) so try to fit it in there then tap it with a plastic hammer or a piece of wood.. get it started .. now find a smaller socket that fits on the end of the bare cross so that you can push the whole thing back the other direction and get the other cap out.



Thats it! Now the first half is free.



These u-joints have an internal seal as you can see.. it almost looks like RTV (I think it probably is). It is best to keep the bearing caps separated and remember which leg they came from (I never do but don't do what I do haha).
Ok, onward and upward.

Here's where this one gets a bit trickier. The side that hooks up to the middle drive has a tapered or angled edge. A regular socket will not fit on here very well and makes it a fumbley mess.. I took a piece of 1 inch galvanized pipe and cut off a chunk.. I think it was about a 9 or 10 degree angle but I ended up fine tuning it on a belt sander. You can see in this next picture, it looks just like a socket but with an angled end this is where again it would help to have a helper to hold it all together while someone runs the vice/clamp.



Now do the same thing again.. push one side out, and then use that smaller socket to push the cross and go back the other way. Now you have the feeling of halfway point. (drink appropriate beverage now).



Now its time to clean it all up. Solvent, carb cleaner or whatevever to clean up the cross, but be careful with the caps. They have seals and you don't wanna mess that up..

If you have a new u-joint then you can skip this part, maybe if you want take the time put a coat of some spray paint on it to protect it for the years. If your just rehabing an old one and nothing has broken yet then you can remove the needles from the caps with a pokey if you want. Clean 'em off and put 'em back in with some new grease to hold 'em in place..

Warning!! Many times I have messed up and dropped a bearing cap and spread the needles all over the place. This probably won't happen to these because of the rubber boot protecting the area.. These will not rust up like on car driveshafts that are exposed to the weather. However I have at least twice been on my hands and knees at the bottom of a grease pit under a vehicle searching hopelessly with a light for those needles.. No joke both times I managed to find everyone, and a few others from old jobsl hahaha..

Its important on any u-joint to make sure that the needles are held in with a little grease and in position. In the case of me re-using this one, after I cleaned em up a little I put some grease in each cap and "shove" it onto a leg of the cross a few times to sort of pump the grease up in there.. then I turn them and push them on and let the excess come out so its easier later (its like a shoe stuck in the mud). Then I will add just a little more so there is some to squeeze out when you finally put it together.



By the way, it had black paint on it already.. All I did was clean it up and repaint it.. (Its sort of my trademark to have a yellow yoke or cross on a shaft somewhere, just for fun but a secondary purpose could be that if you ever had to identify your bike to a cop or whatever, you have a "hidden" thing that only you could know about. Just shine a flashlight into the boot and see that silver and yellow, thats MY bike).
Ive been looking for a place for one of those hidden marks and that seemed like a pretty good one.. ok..

Normally I would reassemble the same way I took it apart. But in the case of those angled ears on the yoke that hooks to the middle drive, I decided to just do both simultaneously.

Warning!!!! This is where you want to make sure the needles are all against the inner walls of the caps.. it is common for them to fall into the cap as your trying to assemble it and get pinched or trapped in there and it is a pain and you might ruin it all .. make sure you put grease in there and run your pinky finger around in there and make sure they are lined up right, and then check all 4 caps on the cross before you start assembling so you know they will fit on.

Ok so you see I pushed the caps on by hand and am attempting to keep the cross centered between the two caps as I begin to squeeze it back together. Inevitably one side moves more than the other so move a little at a time and make sure the cross stays centered so the needles have something to ride on and not fall into the bottom of the caps. A little anti-sieze compound helps here in the "straps" or the cap hole (whatever). Sometimes you have to push/pull pretty hard on the cross to get it to move back and forth because the grease has it hydraulically locked.. make sure it moves back and forth and move in small steps.. keep turning it.. I hate doing it this way.. I prefer to push one side on and past where it would seat.. but not all the way out like when you remove them.. then you have enough of the leg of the cross sticking out the other side to get the next cap started and know its lining up well.



Here you see that I have one side in its place and have put the C clip back in. Then I turned it around and had to use my angled adapter again to push the other side in until the groove for the clip just clears the inner edge of the yolk.

The reason I used the adapter is because you are pushing against the body of the yoke this way and not the other cap. Often times they become too tight when you assemble them. Only after you tap around with a hammer will they adjust and loosen up.. OK then...



Warning!! A word about C clips.
If all is well you should be able to spin the clips around with a screwdriver. And with a little more force, they start popping out of the groove. Try to position them on the "upper" part of the yoke, in other words have the open part of the clip down toward the bottom of the yoke so that the whole clip is on the nice flat that is the upper part of the yoke.

Ok by now you should get the groove of things.. When I painted my parts, I replaced my blue paint pen marks with a few scratches that I made with a file. So line up the yokes the way they originally were and put the second half on. You can do em at the same time like the last one or since the sides of this one are flat you can just push one at a time and ALWAYS keep the cross moving back and forth between the caps and turning a little. Imagine in your mind, all those needles in those caps and you want them to stay on the sides like the tilt-o-whirl.

Here I am doing both at the same time again, as you can see one side is reaching home first so as soon as it gets there slip the C clip in place.. then switch to the other side.. If it's real tight and you're having trouble.. remember the same thing when you took them apart.. a little tension and then tapping with a hammer makes it move. I often will hold the whole thing in my hand or against a bench and hit it with a hammer on either side, on the ends of the caps and around the "straps".. a little of this tapping will reposition things and free up a "tight" ujoint. Then its nice and free moving in your hand; this means it will be the same way when its flying around in a circle at high speed.



Now if any of your paintjob survives all this, you can put a little tape in the middle around the cross and shoot the yokes one more time to freshen things up.. If you even care, I just do it for fun.

Here is how mine ended up. Also in this pic is the adapter I made, I belive I used about a 9 or 10 degree angle but I cut the 1 inch pipe with a hacksaw so ended up adjusting the angle on a belt sander till it lined up right.



Just a note. On a normal bearing, it is constantly spinning and wearing a smooth pattern. Eventually it wears out and becomes loose. On a Ujoint, it never makes a complete circle or anything near it.. Even though it may work well and seem smooth to your hands.. a new one or some new grease combined with repositioning it can refresh it and make it work much better/smoother.

As protected as these ujoints are in there boots, they will truly last a long long time. But it doesnt mean they couldn't benefit from a little loving if you're so inclined. If you need to replace a bad one, I hope this post will help.

Best of luck,
ClarkGriswald
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