Pinion cup

[Ricky-D]

I am not sure why Honda put those holes in the pinion cup. They certainly cost them money to do such and I don't expect they would just throw money away for no reason.

I do not think the holes are for lubrication. There is no positive way lubrication can get to that pinion joint.

I think the holes are for draining purposes.

Honda goes to full measure to seal that whole pinion cup assembly and it seems that a few are not taking into consideration that there is another oil seal that is not pictured in the latest post on his thread but is very important to the total sealing effect.

There is an oil seal between the drive shaft and the pinion cup that completes the seal of that end of the pumpkin. So you see there is a seal installed in the pinion gear retainer nut that seals the outside of the pinion cup and then the seal on the drive shaft seals it to the pinion cup on the inside.

I feel Honda does this because the weak link in the whole assembly is the swingarm boot.

Looking at that rusted pinion cup is telling me that the boot was letting water (rain) pass and run down the drive shaft and into the pinion cup. Honda put the seal there to stop the water but the seal failed. Since the whole assembly is static it is hard to understand the failing of the seal, could possibly be an assembly problem.

The holes are most likely a drain, which to me seems stupid to let water enter the internals of the pumpkin,  whereas Honda also goes to pretty a fairly complex attempt to keep water out of the complete pumpkin.

Like I said: It's all dependent upon the proper installation of the swingarm boot!

Another point I would like to make is that I have never come across where a greased union is also lubricated from an oil source. To me that doesn't make sense since oil would be a natural solvent for grease and would tend to remove the grease from the pinion cup interior.   And in anticipation of the few that will take exception to this premise I am not even considering the concept of pre-assembly greasing of parts that are in finality oil lubricated!

***

[lee]

There is an oil seal between the drive shaft and the pinion cup that completes the seal of that end of the pumpkin. So you see there is a seal installed in the pinion gear retainer nut that seals the outside of the pinion cup and then the seal on the drive shaft seals it to the pinion cup on the inside.

First sentence:  If it weren't for this seal oil from the pumpkin would go into the swing arm.
Second sentence: (seal in retainer nut) this seal DOES NOT cover the oil pick up hole that
continues into the inside of the cup.

[shortleg]

  The two holes are for lubrication from the rear[from pumpkin]
That is where you get your lub from for your pinion cup.
 The reason that they fail is these two holes become plugged with heaveier lubes
that are stuffed into the cup.
          Shortleg[Dave]

[MikeT]

When my pinion cup failed I found that the "oil seal inside the thingy" had moved back and covered the holes allowing nothing in or out.

[Valkahuna]

Let's use some common sense here: Why would anyone design anything with drain holes to let water into a sealed unit filled with oil? 

The truest things said here is that the holes cost money, so they serve a purpose. Couple that with the statement above and you've got your answer.

And if that is not enough, the drawing of the assembled unit does a cursed good job locating all of the components in question.

[Robert]

As a point of information I have sealed up as much as possible the tube where the drive shaft goes so nothing gets in there. I thought that may be a problem too but no

[John U.]

Lee are you sure about the direction of rotation of the drive shaft? I played with the rear with different greases and oil levels in the pinion cup and what I found was the oil from the rear didn't do such a good job of getting to the cup but the grease in the cup did a real good job of getting in the rear oil. I also wonder has anyone used moly in the rear end oil?

I use moly in my rear end oil. I add dry moly to it until it's a pleasingly dark color (very scientific method). I also add it to Green Grease (for the splines and cup) until it's not green any more.

The splines are never dry when I change tires, and they look like new so I guess I'll stick with it. Plus the fact that I have a box of moly powder to use up.