Updated warning on greasing the rear drive shaft (1 Viewer)

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As many of you know, overgreasing the zirk fitting that feeds the rear shaft spline can lead to the shaft being essentially "hydrolocked" and doing damage to the center diff or rear diff due to enormous force they are not designed to take longitudinally.

The other day, I greased the shafts and again had trouble getting any grease in the rear shaft. Today I was under the vehicle to grease the birfields and noted that no grease had come out the splines in the intervening days. Strange.

So, I pulled the shaft off for the first time ever and had a look. I've always wondered what I'd find. Poor machining in the grease gallery behind the zirk? Dried grease blocking the splines? What?

I cleaned out both halves (male/female) which took an hour and a half and a lot of degreaser. Finished up with brake cleaner. I could see no evidence of ANYTHING amiss. The only thing I did not expect to find was a dust seal on the female end that had an interesting contact area made of fiber. It looks like the non hooking side of velcro and was very tight. I suspect this is the culprit as it provides a surprisingly tight fit once saturated with grease. The fibers may provide an incredible amount of force preventing grease from getting through. So I'm going with this.

On my shaft, I switched to red Mobil 1 grease 5 years ago. So, perhaps 10 consecutive greasings. Wanna know how much of this had made its way through the splines to this seal? Zero! It was all trapped in the end and the splines and this strange seal were full of completely black grease that may have been original. Incredible.

I'll update over the next few weeks to let you know if the purple grease I put in it is able to get past the seal as I'd expect a design like this to allow. Everything was perfectly clean and I hand packed the halves before reassembling, so if the design is going to work properly, I should know soon..

In the mean time, use extreme caution on this as I was struck by how effectively the seal prevents fresh grease from getting where it needs to be, which means the shaft is capable of exerting damaging pressure for a very, very long time after you grease it.

DougM
 
Doug,
Thanks for the post.

Question for ya. I'm swapping out my rear driveshaft (candycaned during last wheeling trip) for an older one I have that was re-tubed. Any idea if they take all the grease out when it's re-tubed? I assume they would. So I'm trying to figure out how much grease I should put in there before I toss it back on.

I think I'm not going to get the current one re-tubed, and just toss it on before wheeling trips. Less to worry about that way. :D
 
I replaced the short ends (the male i think, its the one with the u-joint on it) with a used one.
I put it on my driveshaft and it lets grease out.
I don't know if its from being clean or its from one or the other has more wear on it.
The front driveshaft lets grease out too. I cleaned that one.

I wounder if its best to release the pressure after greasing by pushing in the zirk? Or would this just let out the grease I just put in?

I hope that an over greased driveshaft is not what killed my t-case. I think I had a bad bearing that heated up which heated up the VC to the point it locked up.
I asked a trany shop and he said that it shouldn't but what does he know about VC centerdiffs?
The worst part is I have a new bearing for the rear output shaft but didn't replace it :(
$2000 later I don't have an "unwanted self locking center diff".
 
kurt ,What did you get for $2,000? A new transfercase? I'm a lil concerned that my vibration woes may be the input bearing on my transfer case. Several months agao after greasing my driveshafts I was told by Christo and c-dan that I may have overfilled them and this could act as a hydraulic ram and trash my input bearing on the transfer case. Christo suggested I remove the zerk and drive it on a bumpy road a bit and let it flex to push any extra grease out. Well I of course did this but never noticed any grease that may have come out or flew onto surrounding areas.So what did that 2,000 get ya?

Thnx, Vince
 
Junk,

Funny you should ask how much. I have been thinking about this all evening (between dinner with the inlaws, playing with the kids, and running the sprinklers). And I think I've got too much in there. Before assembly, I greased the splines and left excess on the female side so the male side would distribute it on down the splines I could not reach. Once it was on the truck, I then pumped some in until the shaft moved as I normally would. I know there was air in there as I did not pack it full, yet I heard no crackling sound of air coming through grease under pressure.

But think about this. When I emptied the shaft of old grease, I did so by removing the zirk fitting and compressing it fully. Solid grease came out - no trapped air. So that was my intent by pumping some in after it was back on - to remove the trapped air from reassembly. However, if I did succeed in doing this, I'm essentially hydrolocking the shaft at the length it is while parked, which is the way it has been for years. Why? Well from my experience the seal is so tight it will not allow grease to come out - certainly from a quickly applied force like hitting a bump. And the opposite is true as well, meaning when the truck needs to elongate the shaft there is not going to be much/any movement either.

This made me wonder how ANY splined shaft actually allows movement if there's solid grease in there. So, I'm going to email a few driveshaft specialists about it but I'm interested in the thoughts and observations of the group. In the meantime, I'm going to remove the zirk fitting, drop the trailer on it and deflate the air springs to allow the shaft to force out a lot of grease. Then I'll take the weight off and the shaft will suck air in via the zirk fitting hole and I'll put the fitting back in place. Then I've got a compressible compartment of air in there and the splines are definitely greased - best of both worlds. Air is easily compressed and will transmit less force as the shaft length changes.

My questions center around what happens over time as repeated greasings (even "correct" few pumps) eventually replace all the air with grease? My feeling is you've then got an uncompressible shaft again, right?

So Junk. In sum, I'd recommend you grease the splines, both male and female and leave some excess in the female part that will be distributed along the part you cannot easily reach (fairly deep). Then install it without the zirk fitting in place and you'll have an air cavity that's compressible. Then install the zirk fitting and you're good to go.

DougM
 
Symptoms of overgreased rear shaft?

What are the symptoms of an overgreased rear drive shaft?? I had a 96 4Runner with a rear shaft that seemed to compress while breaking towards a full stop and then release with a noticeable thump. Once I thought I'd been rear ended! I'm experiencing a similar but softer thump (randomly) on my stock 97 LX at take off (soft acceleration). The solution for the 4Runner seemed to be to pump the shaft full of grease until it started to extend........this solved the problem.......not so for the 80?
 
Its not that difficult. there are two ways.

Take shaft apart, grease splines by hand, reassemble shaft.

Pump grease in grease zerk, take zerk off, compress shaft to remove excess.

If you are pumping so much grease in the shaft that it expands while mounted, that is waay too much.
 
My local driveshaft guy gave me some advice on my 60 driveshafts. He told me that after he retubed it (he didn't clean it out) that I should clean it out with parts cleaner and use a bottle brush to completely scrub the inside. Then I should let it dry out overnight. Then apply antiseize to the splines and put it together. Then I should install it and grease it until grease slightly came out of the end. Then remove the zirc and jack it up. It was a lot of work but travelled a lot better after doing all of this. I bet there was 3" of compacted mud/grease in the bottom. I wasn't getting full extension of the shaft.
 
Eric,

The only part about that good advice that won't work is the part about grease "slightly coming out the end". On my shaft, and presumably other 80's as well, no grease can get out it's so tight. I seriously doubt I'm going to ever use the grease fitting on the rear splines again as clearly mine is so tight there is no movement of fresh grease through the splines so all I'm doing is hydrolocking the thing. Now I've got a void of air trapped in there and the truck seems to ride notably better. Of course I've said that before after greasing the shaft, which I now know is malarky since the original (and still fine) grease has never been displaced out of the splines. Can you say placebo?

DougM
 
I can't say I've spent a lot of time under the 94. I greased it when I bought it. The 91 does have grease that comes out of the splines. Maybe it doen't have this gasket you speak of?
 
I have a nice grease line where my grease exits the end of the tube opposite the zirk. After every greasing I get a nice burning odor from what hits the muffler. Don't know why you guys are not seeing the same thing. As for the hydro lock issue, I thought there was a plug located at one end to prevent that from being an issue. I've always pumped it until there was a little expansion at the yoke and then let the flexing push the little excess out through the splines.
 
$2000 is for a NEW TOYOTA T-case.

Christo says he has replaced the out put bearings on some t-cases. I would like to know why and how he knew to change them.

I just looked at my old output bearings and they look and feal ok.
Wouldn't the bearings look blue if they were getting real hot?
I didn't try removing my rear driveshaft to see if that would stop the overheating t-case.

I have a grease spot on the muffler and on the motor.
Look and see if there is grease on the male shaft. I can see it when the vehicle is on the driveway. You may need to jack up one end to see the grease.
If you don't see fresh grease (if you have been greasing it) then you need to take it apart and clean it.
 
Rick,

There is no provision for a "blow off valve" though I also heard that. It's solid and the splines are extremely tight. I suspect a worn shaft that perhaps was not lubed at some point would have more space for the grease to get through. The grease seal was amazingly tight - requiring a push to slide down the shaft. Nice for keeping stuff out and clearly it had done its job. Mine's got some nice purple grease coming out now, but I don't know how much of that was because of the excess grease right at/on the seal from inserting the splines through it or if it's now operating correctly.

Either way, here's a little vignette I forgot to post about the removal/install of the shaft. When I got it installed as described above and pumped more in until the shaft barely began to move - as usual and as has been recommended here by me and others. Then I got in it to take it for a drive as I always do in case someone else were to take it out and hit a big bump right away, figuring I'll drive it around a bit and let the excess grease work through. Couldn't get it out of Park. Had to use notably more pressure to get it out of park. So I'd put enough pressure on the drivetrain longitudinally to cause shifter alignment issues. Took it for a slow crawl around the neighborhood - perhaps 2 miles of drivning at walking speeds. Came back into the garage and there was still an issue getting it in/out of park. That's when I decided to pull the zirk and let any pressure come out. Alternatively, you can simply use a screwdriver to push the little spring loaded ball on the zirk and let grease out. I started this way and was surprised at the pressure of the exiting grease. It's wise to remember that a simple hand grease gun can generate incredible amounts of PSI.

So, clearly cleaning the splines (though as mentioned I didn't find the expected dried crusty stuff blocking them) did zero to help grease come through them. They're just incredibly tightly machined and my feeling is that I'll pull the shaft apart every couple years and simply clean and hand grease them from now on.

DougM
 
Personally I think some of the issue is with the grease being used. I did Eric's front end a few weekends ago. He got some M1 synthetic stuff. Man is that stuff thick! After packing the wheell bearings and installing the front hubs, the hubs were very hard to turn with no pressure from the 54mm nuts compared to what I've experienced using a simple high temp wheel bearing grease hubs fully installed.

All the added benefits of synthetic products are a waiste if they can't get in there to do the basic job of lubricating.
 
Rick - you might have a point there. I tried using Redline synth grease in my grease gun a few times and it just wouldn't not pump (too thick). I put in regular dino grease and it works fine. Real frustrating.
 
I concur, as I have posted in the past, that the best way to grease the driveshaft splines is to remove the shaft and put the grease right on the splines. I don't see any way the pumping grease in the driveshaft will be effective unless you pretty much fill it solid. I guess the theory must be that when the shaft is spinning centrifugal forces force it to spread out both radially and longitudinally.

If you are going to remove the shaft, please note that the nuts that fasten the rear flange are serrated lock nuts. So you want to turn the bolt head, not the nuts. If you turn the nuts you will wear down the serrations, and thus lose the self locking capability.
 
grease seems to come out normally out of the shaft end in my 97...
E
 
fllintknapper

e9999 said:
grease seems to come out normally out of the shaft end in my 97...
E

Mine too ('97)....not alot, but enough to sling grease on my muffler. Both shafts have a good tight fit at the splines and they do move just a bit when you grease them.
 
My rear shaft will spit the grease out of the zerk when I fill it, but the front does not. The rig was poorly lubed when I bought it (July this year) so I've perhaps been a little too focused on lubing (as if I could make up for past neglect) and have been, incorrectly as I now know, pumping until I just get a little movement in the shaft. As mentioned previously, I've noticed a bit of a thump when accelerating from a stop, though it is delayed a second or two past when I hit the gas and only seems to occur when the rig is warm. Sounds like I better pull the zerk off the drive shaft and check it. After doing the Rubicon three weeks ago I also developed a leak in the xfer case tail stock. I've been checking the fluid ever other day while I'm waiting for parts to come and had assumed the "bump" might be due to this. Any thoughts?
 

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