Re: Greasy opinions
MicaBlue03 said:
So the torque issue that started this thread is the easy part--it's the greasing technique that's really worth discussing!
TechWrench, I too would suspect that when greasing the spiders the grease would come out of the "easiest" seal first and never out of the rest. But while grease is a fluid, it's thick enough that it doesn't usually work that way. Only the most loose or worn farm equipment that I've greased acted that way. Sometimes it takes an extra pump or two, but grease distributes itself surprisingly well, even in summer.
I don't think there's a problem with forcing some grease out of the seals of the cups at the end of the spiders. The seals are oriented to allow that, and it does serve to drive any contaminants out. I just think it isn't usually necessary unless you've got a dust or water concern.
The slip joint is tougher to be sure about. Grease gets dirty but isn't actually "consumed" in these joints, so if you lube them with any frequency and with any significant amount of grease, they will eventually get full. I don't see any mention of vent ports or avoiding overfilling in the repair manuals, so I suspect that a big bump (and the subsequent compression of the spline joint) will occasionally cause grease to be driven out of the joint. I've watched and haven't seen this yet on my vehicle, but I can't see how it could be any other way. I worry about the resulting end loads on the differentials and transfer case, but not very much; I've simply never heard of this being an actual problem.
In the end, we may be making too much of a small matter, and both of us will be doing nearly the same things. If the joints aren't regularly subjected to dust, water, etc. then a broad range of occasional greasing strategies should be sufficient. If you've got salt or other corrosive stuff on your roads in the winter, then driving a little old grease out of the spider cups periodically may be a good idea.
BTW, I reviewed the repair manuals today and was unable to find any mention of dismantling the shafts as a part of lubricating them. They simply say to wipe off the joints before pumping in some grease. Dismantling the joint is described only as part of a replacement or overhaul of the shafts.
Lastly, given the fact that I was unable to buy the two different types of grease they call out and just used Mobil 1 synthetic instead, I'd be interested in any opinions or experiences with the separate grease types. After talking to local dealers it's clear to me that they use just 1 type of grease and it's probably not synthetic, and I'm not even sure they do that very often.
We could debate the process and value of lubricating u-joints for ever and there would always be differing opinions. My personal feelings, for what is worth, is that some lubrication is better than none, but too much serves no value. But given the way u-joints function, there is actually very little movement between the end caps and the center cross ends. I doubt that on most normal height vehicles, there is more that 10-15 degrees of rotation. I have replaced hundreds of u-joints over the years, and I believe that most would have failed eventually, no matter how they were lubricated. If you consider it should only take most technicians half an hour to change both u-joints in a shaft once it is on the bench, is is really cost effective to spend too much time on excessive lubrication of a component that will still eventually fail?
" BTW, I reviewed the repair manuals today and was unable to find any mention of dismantling the shafts as a part of lubricating them. They simply say to wipe off the joints before pumping in some grease. Dismantling the joint is described only as part of a replacement or overhaul of the shafts."
I may not have been clear in my earlier post, but I was refering to the slip joint in the shaft, not the u-joints. I can't imagine anyone attempting to dismantle the u-joints to clean and lubricate them and reinstall them again.
"The slip joint is tougher to be sure about. Grease gets dirty but isn't actually "consumed" in these joints, so if you lube them with any frequency and with any significant amount of grease, they will eventually get full. I don't see any mention of vent ports or avoiding overfilling in the repair manuals, so I suspect that a big bump (and the subsequent compression of the spline joint) will occasionally cause grease to be driven out of the joint. I've watched and haven't seen this yet on my vehicle, but I can't see how it could be any other way. I worry about the resulting end loads on the differentials and transfer case, but not very much; I've simply never heard of this being an actual problem."
I will have to do a search here and on the other site, but I am positive that at least some individuals have experienced severe banging in the suspension when they completely filled the slip joint with grease. If I remember correctly, one individual was chastized by the dealership when the mechanics had to remove the driveshaft and empty the excess grease from the joint so it wouldn't bang any more. I also recall one individual reporting that the dealership actually drilled a vent hole in the female end of the slip joint to relieve that symptom. IMHO, I think that was a poor decision on the part of that mechanic. Moisture could easily be drawn into the joint through the 'vent' and cause wear and failure later down the road.
I guess it boils down to this. I am a firm believer in normal preventive maintenance on any machine, but I believe that over doing it will not provide the 'imortatility' that some people think it will. A very wise mechanic I once knew taught me early in my career to always remember; No matter how well made it may be, EVERYTHING put together by man sooner or later falls apart.

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