I had the infamous clunk a few seconds after starting to roll from a stop.
First I tried greasing with some generic grease, just a few pumps into the driveshaft spline slip joints (but not overgreasing) plus routine u-joint greasing. Still clunked.
Then I took the rear spline apart because the clunk seemed to be from the rear. There was nothing apparently wrong, some grease inside. But the grease in the spline area seemed somewhat thin, perhaps a result of separation in service.
So I cleaned the spline slip joint internals and put it back together, and greased it again with generic grease, directly on the splines prior to assembly and also a few pumps into the zirk. This seemed to reduce the clunk somewhat, but after a couple weeks it started coming back.
So finally, I overgreased the spline/slip joints with moly grease thru the zirks, until grease was visibly spooging out past the lip seal. This cured the clunk. Have not heard the clunk for a few years now, have not regreased.
Thoughts:
1. The Toyota factory service manual (for LX) says to grease until grease is seen escaping past seals. This may mean it is actually a proper service technique that causes no harm (if manual is correct). Page PR-7:
"HINT: After installation, pump MP grease into each fitting with a grease gun until the grease begins to flow around the oil seal."
(I think "MP" means "multipurpose". This is evidently where Toyota missed it, regarding the need to use moly in this application.)
2. The splines are evidently prone to "stiction": When vehicle is stopped, idling in D and held by brakes, the static angular (torsion) driveshaft load sets the splines semi-stuck together in a nominal axial (driveshaft length) position (due to neutral height of rear end). As soon as vehicle starts to accelerate, rolling from stopped position, the spline contact force increases due to angular (torsion) forces in the driveshaft, at the same time sliding forces between splines increase as the rear driveshaft is compressed by the rear end being forced down as vehicle starts to accelerate. If there is inadequate lubrication in the splines to prevent stiction, they will momentarly stick (static friction) then break free and slide (dynamic friction). This causes the clunk. The solution is to get enough lubrication between spline sliding surfaces to prevent stiction. ("Enough" also means "correct" lubrication - MOLY.)
3. Greasing with only a few pumps does not really force much (if any) grease into the spline area. It may only put a few dollops of grease into the cavity at the end of the internal shaft, with very little (or no) grease being forced into the splines. Therefore greasing must be overgreasing, until grease spooges out past the seal. This will completely fill the cavity and force some grease into the spline area, and also, additional grease will slowly work its way into the splines over time in service helping to keep the splines greased.
Regarding concerns about axial (thrust) force increasing due to overgreasing, and possible resulting damage to bearings in tranny/tcase/differential: (a) The slip joints already exert significant thrust force in service because they are sealed so well that they act like air springs due to air trapped in slip joint cavity, so overgreasing does not create thrust forces where none exist without overgreasing, and (b) the tranny/tcase and differential input bearings will already include thrust bearing provision in their design, because this is a common design factor. As noted I've been running overgreased for a few years now with absolutely no resulting problems.
4. Moly grease MUST be used to alleviate the clunk problem. (Caution: Moly is toxic, don't eat the grease.)
Tinkerer's .02 worth. (Nearly a dissertation but a simple problem really.)
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