4RUNR

Where does the old grease go? Doesn't seem like it goes anywhere.

I tried greasing the slip yoke again after 5000 miles and it seems to be full. Any amount of grease I put in has to come out, or the slip yoke won't fully compress.

Is there a diagram of the internals somewhere on the net to figure out what's going on inside?

4RUNR

I'd settle on an explanation what's inside that thing too.

4Crawler

iTrader: (3)

Nothing inside really. Just a male and female spline in there and room for the male spline to compress. When I grease mine, I try to apply about the same amount of grease that the u-joints take. Too much grease is probably worse than too little. Why? If you keep pumping grease in, you'll fill the empty space with grease. When the shaft tries to compress beyond it's normal position and it could bottom out in the grease (hydraulic) and possibly damage the t-case output bearing. There is usually a weep hole at the end of the shaft to let excess grease escape, but bottom out the suspension hard and that may not be enough to relieve the pressure.

What I do periodically is to pull the slip yoke apart and brush some good grease on the splines to ensure it is getting evenly lubed (make sure to mark the the alignment for later reassembly). It is not really a high speed joint like a bearing, so it just need a little grease to keep it sliding freely.

CynicX

as 4crawler said its just splines like on a axle shaft...

the thing I dont understand is I thought you pulled the yoke apart to lube it? How do you do it without pulling it apart? Thanks

4RUNR

CynicX, you are way out there, dude

What I'm curious about is how the grease is channeled through that thing. There is definitely no pressure relieve hole in mine, as I've mentioned that it stops compressing once any more grease is added.

Adam F

Just pull the drive shaft apart at the splines, and smear some new grease on the male splined section of the shaft.

4Crawler

iTrader: (3)

There is usually a grease fitting (zerk) on the end of the female section of the spline. You can see the one on my rear shaft, about a foot up from the rear differential:



Often, it'll get scraped off in the rocks. The grease pumped in there mainly goes to one side of the spline and you could easily pump in a whole tube of grease and never see any come out the splined end.

As noted, there is nothing inside, just imagine a hypodermic syringe, except with splines instead of a rubber seal on the plunger. There should be a small plug or weep hole inside the yoke of the u-joint on the end closest to the slip yoke. If none is there, you might consider drilling a small hole. I have seen shafts with both a metal cap with a weep hole and others with a rubber cap that fills the hole and others with a big gaping hole in the end.

CynicX

ohh lol...i am way out there...

I did my jeep and s10. Just unbolt the driveshaft and slide the slip yoke out. Clean it off and brush or wipe on new grease.

For some reason I thought you meant you wanted to know what was in there but youve been lubing it through some other method.

Edit: Oops I went out and looked at my Taco and its not like my Jeep...SY is in the back and there is a zerk....heheh looks like I have something to do tomorrow....heheh

That should take care of a little of the axle wrap issues I'm having

4RUNR

Precisely, I've been using the zerk fitting, which is on the male end on the 3rd gen, and I’m getting a feeling that it is not compressing right and putting pressure on my differential.

Now 2 questions arise: if I take off one of the ends of the drive shaft, the slip yoke will separate without any special tools or superhuman strength? And second, what tool is used to remove the bolts, as there is not enough space to put a socket on either side, which consequently means no conventional torque wrench.

4RUNR

4Crawler, by the way, it looks like you can actually see splines on yours, where as you can see it's very different on the 3rd gen. Was you claim that it will come apart hypothetical or experience?

4Crawler

iTrader: (3)

No splines visible on mine above, that is an aftermarket shaft, all Spicer and Neapco parts. It has a small smooth section on which the end seal rides then a larger section that is splined, that stays inside the tube. At the most, you may have to pop a seal off the end of the female section of the slip yoke. Looks like yours is a different design, not familiar with that exact setup, but all mine (stock 1st gen and aftermarket) all just pull apart.

Here is one of my spare shafts, has what looks to be a stock u-joint yoke with an ond grease fitting on it:



And yes it does pull apart. The old fitting now goes nowhere and there is a new fitting up on the female end of the splines.

What you might try is unscrewing the zerk and then compress the shaft and force the grease out that hole. To unbolt, get a pair of long handled 14mm wrenches and have at it. I don't use a torque wrench on mine (won't fit), and just squeeze the two wrenches as hard as I can in between my two hands for tightening.

4RUNR

That's my plan of actions for the future. I'm highly surprised though that it seems to bind in certain position if I rotate the shaft, and no more grease is coming out if I hold the zerk open with a needle and have someone jump on the back. Something is going on inside.

JBSTRD

What happens when you put grease in the zerk is that it fills the hollow tubing of the slip yoke and makes contact with the end of the splines. The pressure then forces the grease into the crevases of the splines, in turn greasing the splines. What happened to me is that I went to grease that zerk and it all came out in the back of the yoke where there is usually a cap. I found out that I had greased it too much and it had popped the cap off that holds the grease in. So, now I just drop the driveline and grease the splines and the sleeve manually.

Jason

4RUNR

Well, all that effort of taking it off did not improve the situation.

The slip yoke assembly came apart smoothly and without any difficulty. There were no seals of any kind. Inside was greased very well, with a good reserve of grease everywhere. Grease was not dirty and still viscous.

I took out all the grease by dissolving it then wiping it squeaky clean; then applied a light coating of new grease. Assembling it back was no trouble either. The slip yoke travels the whole length very smoothly, but the assembly is AIR TIGHT! When I compressed the yoke the zerk fitting starts whistling, as that is the only path for the air molecules to escape, and here in lays the problem me thinks.

Before and after this “cleaning”, if the back end is bounced using hands there is a very pronounced clunk coming from the area of the U-joint near the differential. The fact that the slip yoke is virtually air tight leads me to believe that it simply can’t compress fast enough and is putting pressure on the U-jonts and the differential.

Now, the pressure safety cap is unmoved, which I guess means it is still far from causing damage, BUT, is this clunk normal?

aowRS

Very interesting post. I've wondered the same when pumping grease into mine.

How about unscrewing the actual zerk fitting (temporarilly) and then bouncing the truck to see if this allows enough of a pressure change.

Andreas

CynicX

so if you can over fill it how much should you pump in?

4RUNR

aowRS, that's a brilliant idea to prove my theory! And I just tried it.

a.) I stuck a thumbtack in the zerk to hold it open, and the clunk was still there.
b.) I took off the zerk completely, and there is clearly air swooshing sound and no more clunk!

So now there is no doubt that the pocket of air inside does not allow it to compress, fast enough, and there is definitely no factory breather hole in sight.

CynicX

thats odd it would make a "clunk" sound....are you u-joints alright?

I'm thinking that maybe a loose joint is clunking when there is so much pressure on it compressing the grease. Pushing the air in and out though doesnt cause that kind of pressure.

seems weird since there isnt anything different about your slip yoke then anyone elses but yet there is a clunk when compressed.


I know you can get a clunk coming to a stop from axle wrap. But it shouldnt do it unless you press the brake while the slip yoke is extended or compressed. And it being dry it might "stick" then clunk when you left off the brake....

4RUNR

To be more specific the clunk is coming either from the U-joint near the transfer case or whatever that thing is called that comes out of the transfer case. With the zerk removed the slip yoke moves much more freely too, so there is definitely a benefit to having it vented, don't know why it wasn't from the factory.

There is nothing wrong with the way it drives or sounds while driving with the zerk in. If I didn't try bouncing it while parked there is no "problem".

aowRS

It would be great if a magical breather assembly existed that allowed you to grease the slip joint with a regular zerk, then remove it and replace with a breather for daily use. Unfortunately that would immediately clog from the the inside with grease....

Let's keep this thread active - I have wondered about this long enough.

Andreas