Can I get some insight on my rearend?

[John97]

I put a new driveshaft in my bike 3100 miles ago. I recently started getting dirt collecting around the differential vent. Searching seems to suggest it’s overfilled. I have changed the fluid multiple times over the last 60k+ miles since I do it roughly every 6k or so when I replace the rear tire. I follow the Clymers book…bike vertical, filling to the lower edge of the fill hole but this is the first time for seeing evidence of oil vapor or whatever through the vent. Each time I use Lucasoil 80-90.

Seeing a couple dirty looking drips I figured since I was there I’d drain and refill the fluid. Upon doing so I see the oil in my clean drain pan has a silverish sheen to it that I don’t recall seeing before and it looks quite dirty although I’ve never drained it at 3100 miles before either. I see no shavings or grit or abnormal wear on the gear teeth. I used Moly paste and grease where each was required per this forum, installed a new pinion seal and three orings. There was a little mud looking substance in the center of the drain plug, I’ve seen it before. When I wipe it out it smears between my fingertips.

Does the venting mean anything? Did I overfill it this time after filling it correctly several times prior?

Is the sheen in the oil indicative of another problem or something to keep an eye on?

https://imgur.com/a/gtAEAcS

[Chrisj CMA]

If you change the fluid during tire change. Just drain and fill the final drive while it’s off the bike. With it laying flat on the workbench or floor, just add 150cc of oil.

[mello dude]

Terrible title man... there's  a joke in there.....

[John97]

Well I would hope so, much thought and effort went into that title.

Nobody has any thoughts as to the sheen I saw when I drained it? Maybe it disappears with additional mileage? Like I said 3000 miles is half if not less of when I usually change the fluid perhaps that’s why I’ve never seen it before. I dunno.

[Hook#3287]

I learned on a different web site that if you move the rear tire or wheel before swapping the pumpkin oil to the correct level, a lot of oil is coating the gears above the fill hole and your in fact overfilling.

The correct process is to drain completely, maybe over night, before filling.

It's good advice to change the oil when doing a tire swap, but sometimes the stars just don't line up.

The oil sheen is a puzzle.  Are you sure the pan wasn't contaminated somehow?

[Challenger]

I guess I've never checked to see how full the diff is after changing the oil. Never had any seepage at the breather. I always just measure 5.1 Oz and pour it in. It's usually on the bench when I do it so not easy to check untill on the bike. I do use synthetic oil and have seen a slight sheen you describe a few times, but at 153000 it still seems to be runing fine.

[98valk]

Lucas gear oil has received many many bad reviews over the yrs, esp., about it foaming, meaning air gets entrapped in the oil. air doesn't lubricate.

here is how to find a great gear oil to use.
http://www.valkyrieforum.com/bbs/index.php/topic,110541.0.html
    
How to select a good gear oil based on VI index.
« on: March 30, 2020, 11:41:52 AM »
   Reply with quoteQuote Modify messageModify Remove messageRemove
https://www.machinerylubrication.com/Read/28956/lubricant-viscosity-index

High or Low Viscosity Index needed?

If conditions are not constant (variable loads, variable speeds, variable ambient temperatures, etc.), then there is a need for not only the optimum viscosity but also a high viscosity index to stabilize the optimum viscosity. The more variable the conditions, the greater the need for high VI oils.

Also, keep in mind that for a great many machines there has been no past experimental or theoretical effort to identify the optimum viscosity. Viscosity selection is more of a wild guess. This too calls for a high VI lubricant.

A lubricant may merit having a high VI for one or more of the following reasons:

    The optimum viscosity is not known
    Varying loads and speeds exist
    Varying ambient temperatures exist
    To boost energy efficiency
    To boost oil service life (lower average temperature)
    To boost machine service life (fewer repairs and downtime)

I add this to the gear oil I use
https://www.tsmoly.com/additives-moly-gear-concentrate-p-163.html

they use to have a smaller container when I bought it over 20 yrs ago. call Vincent to see if he can get u a smaller container. He is a great guy, I've talked to and emailed him many times over the yrs esp about the spline grease.

maybe the best spline grease to use.
https://www.tsmoly.com/grease-spline-grease-p-367.html