We are often asked about the frequency or type
of grease to use when servicing a drive shaft. The answer has always
been; "we believe a frequent and thorough greasing is more important
than the type of grease you use". This is primarily because, one of
the main results of a proper is a "flushing out" of any
contaminates. It seems that a little grease and dirt make an
excellent grinding compound. While greasing, if you pump in grease
until you see clean grease come out past ALL the seals, you will
insure that most of the contaminants will be washed away.
We've taken a look at the lubrication recommendations from some
Spicer universal joints (greasable and non-greasable) on my shelf
and they read as follows:
- "Spicer Re-Lube Light/Medium Duty..."
- "Lithium base greases meeting NLGI Grade
1 or Grade 2 are preferred..."
- "Spicer Pre-Lube Light/Medium Duty..."
- "Do not add lubrication Do not mix
bearing caps on journals..."
- "Miss-matching of cups on cross will
result in improper quantities of lubrication in cups causing
premature joint failure..."
- "Addition of lubricant may damage bearing
cup seals leading to premature joint failure..."
The NGLI is the National Grease Lubricating
Institute (it's probably a pretty boring place). It is the umbrella
organization that sets the standards for the properties of different
greases, oils and other lubricants. Again, although we are not
authorities on the subject, we do know that the grade will typically
refer to the viscosity of the lubrication, with a grade 1 being less
viscous than a grade 2. The lithium is the base to which the
lubrication is added. In this case, lithium is basically a soap
base. There are other bases to which the lubrication can be added,
Molybdenum Disulfide for example, which is typically referred to as;
a "moly" grease.
Beyond that there are a few general parameters that we would suggest
in selecting the grease. Temperature rating should be at least 300
degrees. This may sound awfully high but it wouldn't be uncommon for
the drive shaft to reach an operating temperature of near 250
degrees and it's important that the lubrication doesn't separate
from the base and boil off.
There is also a load rating to consider. Theoretically at least, if
you can prevent metal to metal contact, you will prevent wear.
Greases and oils will have what is known as a "Timken Load Rating".
We are not qualified to explain all the technical information of a
Timken Load Rating, it is basically the rating of the lubricant to
withstand certain amounts of pressure before smearing so thin as to
allow surface to surface contact. The Timken Load Rating should be
sufficient for the intended use. Most grease will probably be
adequate with the exception of thin motor assembly grease.
The viscosity should be in the range that will allow for a good flow
past all the wearing components while servicing. Again, this is for
the "flushing out" of the contaminates while servicing. Very high
viscosity in the grease may actually be detrimental as higher
viscosity grease tends to create more heat than would a more freely
flowing grease. Remember to that ultimately, heat is one of the real
If you run in a lot of water or mud, it may also be good to use a
grease that has water resistant characteristics.