Why black final drive oil?

[nwguy]

I changed all fluids in my 99 Bassa as part of its restoration. All fluids were inky black and way overdue for changing. Then I found a leak in the rubber boot on the drive shaft. I drained and refilled the final drive as part of replacing the boot and found the fluid to be inky black again after riding only a few hundred miles. Thinking that the gearbox and engine oil might also be black I changed all 3 fluids one more time. Gearbox fluid like new. Engine oil still pretty clean. Final drive fluid, inky black again. This after very few miles.

Is this normal? Why would my final drive oil get so dirty so fast? I'm using Lucas brand 80-90 weight gear oil in both my final drive and gearbox.

[Wayne Orwig]

Did a previous owner/service use moly additive? That additive used to be required, and it is very black. It settles out in the bottom of the drive and would turn the new fluid pretty dark.

It is fine to leave it alone. Before your next change, ride the bike to stir it up first maybe.

[nmroadrunner]

Ride it and change it again one more time or two...see if that doesn't clear up

[nwguy]

I always ride at least 20 minutes before changing any of these 3 fluids. Yeah, it's only 250ml and easy to change. I will do it at least one more time before calling it good. I don't know much about the previous owner's maintenance history.

[PeteS]

As Wayne says is likely Moly additive. Guzzi has been recommending it in the final drive for decades.  Can’t hurt and will likely help.

https://www.ebay.com/itm/263965643289


Pete

[TN Mark]

Many years ago Moto International sold a moly additive called Power Punch. It was very thick and very black. Many, many Guzzi owners used Lower Lunch. Yes, it never really gets fully drained out and will turn fresh gear oil black in no time.

[Perazzimx14]

I guess the question is with modern synthetic gear oils that are readily available in a variety viscosities is moly additive really a necessity or just one of those thing we think we need to do?

Do other manufacturers with shaft drive call for moly to be added to the final drive?

[Kev m]

Many years ago Moto International sold a moly additive called Power Lunch. It was very thick and very black. Many, many Guzzi owners used Lower Lunch. Yes, it never really gets fully drained out and will turn fresh gear oil black in no time.

Wasn't it Power Punch?

[Wayne Orwig]

Wasn't it Power Punch?

Yep. I suspect I still have a lot of it on the shelf.

[TN Mark]

Yes, Power Punch.

And no, it’s no longer needed according to the manufacturers instructions. Some people add stuff more out of habit I guess.

I’ll bet I have a bottle that’s over 20 years old by now.

[n3303j]

I've replaced 3 roller bearings in final drive units that ran moly additive. Each one "skidded" and chewed up a race.



Couldn't pay me to dump that stuff in a gearbox.

[TN Mark]

I've replaced 3 roller bearings in final drive units that ran moly additive. Each one "skidded" and chewed up a race.



Couldn't pay me to dump that stuff in a gearbox.

This real world evidence is the best and only reason you need NOT to use a Moly additive like Power Punch.

[nwguy]

Wow, glad I asked. Thanks all.

[Wayne Orwig]

I've replaced 3 roller bearings in final drive units that ran moly additive. Each one "skidded" and chewed up a race.



Couldn't pay me to dump that stuff in a gearbox.

The needle bearing, right?

I had to replace one like that also. That was back when I used moly. I used to even add a small touch to the gearbox to help improve shifting. I'm not sure it helped.

About the only thing I use it in now is a touch in the fork tubes. It makes them 'stick' a bit less.