Re: Oil gun for trunnions
Posted: Wed Feb 28, 2018 3:35 pm
Isn't grease basically thickened oil?
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MarkDa wrote:Isn't grease basically thickened oil?
JonB wrote:Bit more to it than that, I think. I'm no expert, but I believe it has soap based agents to help it maintain "greasiness" and this stuff dries out (or maybe the oil content does) over a period of years leaving a waxy, cake-like cruft that looks like dried earwax - which I had to scrape off my trunns, and which indicated to me they hadn't been lubricated in, well, years.
Not to kick it all off again, but my reading says that thick grease can be displaced from the trunnion causing voids which (subsequently) collect water. As Rohan says, the trunnion top seal is basically ineffective here, and I'd say that is true whether you lubricate with grease or oil. Yet since oil is runny, it will be pulled down into the trunnion by gravity and stay there, whereas displaced grease will not. Flip side is that grease will help the top seal do its job, but oil won't. Pros and cons.
That said, I think that the choice of grease or oil is less important than the regularity of service. In other words, if you pump the trunns full of [insert lubricant of choice here] really often, and displace any water or dirt that got in there since you last did it, you should be OK. If you accept that, the only decision you need to make is "how often", and I'd say monthly during the summer and fortnightly in winter, assuming average mileage. And definitely just before laying the car up in winter, if that is your normal usage pattern.
JonB wrote:Now that's a very good point, Rohan.
What do you say to my last post? Is it possible the pressure caused by screwing the king pin in and out of the trunnion through steering can displace the grease at the top of the trunnion?
I'm beginning to think grease is a better approach!