How to replace the gear oil in your final drive


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How to replace the gear oil in your final drive

Postby WingAdmin » Thu Apr 02, 2009 6:08 am



The rear drive translates the rotational motion of the driveshaft, which rotates along the longitudinal axis of the motorcycle, to the rotational motion of the rear wheel - essentially, it turns the rotation 90 degrees. It does this using a pinion gear, much like the pinion gear used in the differential of a car:

Image

The gear oil in your rear drive is essential to the smooth operation and long life of your rear drive unit. Without it, the pinion gear would wear out quickly. Because the oil is subjected to extreme shearing forces, special hypoid gear oil must be used:

Image

75W-90 hypoid gear oil is the correct gear oil to use in the rear drive. The shearing forces of the pinion gears break down the gear oil, so it should be changed regularly, and at least once a year.

1. Ride the motorcycle several miles to warm the rear drive, which thins the gear oil and makes it easier to drain.

2. With a suitable catch pan below, remove the rear drive drain plug and allow the gear oil to drain completely.

* Note * - If you've never done this before, it's prudent to remove the FILL plug first, before removing the drain plug. That way, you won't end up draining your gear oil, only to find out (too late!) that you can't open the fill plug for some reason!

Image

3. After all the gear oil has drained, replace the drain plug, and remove the fill plug.

Image

4. Fill the rear drive casing with fresh gear oil.

Image

5. The rear drive is full when the gear oil begins to run back out the fill port.

Image

6. Replace the fill plug. You're done!

Image



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Re: How to replace the gear oil in your rear drive

Postby colemadad » Wed Feb 03, 2010 4:30 pm

I've always wondered - my 900C had the same thing - what is the nut/fitting on the top of the housing (not show in any of these pics)? Thanks.

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Re: How to replace the gear oil in your rear drive

Postby WingAdmin » Wed Feb 03, 2010 5:27 pm

I think you're talking about this:

Image

That is a vent. As it heats up in there (and it does get warm), the air needs a place to escape, so it doesn't blow out the seals. Similarly, air needs to get back in once it cools off.

If you manage to fill it with too much gear oil, it will blow oil out of this vent as well.

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Re: How to replace the gear oil in your rear drive

Postby colemadad » Wed Feb 03, 2010 6:07 pm

That's it. Thanks - another of life's little mysteries unraveled.

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Re: How to replace the gear oil in your rear drive

Postby bamadave » Sat Apr 10, 2010 9:16 am

Just put in new Mobil-1 75w90 Syn lubricate oil.
While the bike was on the center stand, when the steady flow stopped, I leaned it to the right-side and got some more. I was glad it had a brownest color so I feel like it has been changed with PO's.
28 year old bike and you do not know the maintenence history I was hoping it would not be "coal black".
Thanks for this subject thread post. It helped me do something simple to my bike to help save $ that could make a difference in the longetivity of the pinion gear/rear drive.

thanks,

Bamadave :D

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Re: How to replace the gear oil in your rear drive

Postby WingAdmin » Sat Apr 10, 2010 9:23 am

bamadave wrote:Just put in new Mobil-1 75w90 Syn lubricate oil.
While the bike was on the center stand, when the steady flow stopped, I leaned it to the right-side and got some more. I was glad it had a brownest color so I feel like it has been changed with PO's.
28 year old bike and you do not know the maintenence history I was hoping it would not be "coal black".
Thanks for this subject thread post. It helped me do something simple to my bike to help save $ that could make a difference in the longetivity of the pinion gear/rear drive.


I did something similar - when it had stopped flowing out the drain hole on its own, I squirted some fresh oil in the fill port, to help finish "flushing out" the old oil.

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Re: How to replace the gear oil in your rear drive

Postby lake_harley » Thu Apr 22, 2010 2:56 pm

I just changed the final drive oil in mine and thought it sure would have been nice if Honda had put the drain plug at the lowest point, but it isn't. I decided after the change to ride about 5 miles and then repeated the change. I was amazed at how little oil it actually holds. I didn't pay attention to the amount through the "sight glass" on the bottle, but the two changes couldn't have been more than a pint total, just draining the unit with the bike on the center stand, without tipping it to the right. The color of the oil on the second change was noticeably much cleaner than the first so the amount that remains below the drain plug must be quite small.

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Re: How to replace the gear oil in your rear drive

Postby bamadave » Wed May 19, 2010 3:46 pm

lake_harley wrote:I just changed the final drive oil in mine and thought it sure would have been nice if Honda had put the drain plug at the lowest point, but it isn't. I decided after the change to ride about 5 miles and then repeated the change. I was amazed at how little oil it actually holds. I didn't pay attention to the amount through the "sight glass" on the bottle, but the two changes couldn't have been more than a pint total, just draining the unit with the bike on the center stand, without tipping it to the right. The color of the oil on the second change was noticeably much cleaner than the first so the amount that remains below the drain plug must be quite small.


I agree.

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Re: How to replace the gear oil in your rear drive

Postby WingAdmin » Wed May 19, 2010 3:55 pm

The last time I changed mine, I actually had the rear wheel off, so I opened up the rear drive and tipped it over to drain. Much easier than tipping over the entire bike!

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Re: How to replace the gear oil in your rear drive

Postby warezaholic » Wed Aug 04, 2010 9:36 pm

I have used a simple process; To do an efficient job removing (any fluids from any awkward angle without needing to tilt the bike) the rear gear oil may be drained using a vacume pump, two hoses, and a small jar). One hose Inside the gear box leading into a jar (with two holes the jar lid just the size to fit the hole sizes to seal the hoses to maintain a vacuem, with no air leaks) where one goes deeper in the jar from the gear box and a second, shorter hose leading from the jar to the actual pump. No oil should reach the vacuum pump by keeping that hose nearer the lid, and by making the drain hose reaching nearer the bottom of the jar, and the vacuum hose is inserted only far enough to pull the air from the jar...

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Re: How to replace the gear oil in your rear drive

Postby comanche » Fri Apr 01, 2011 6:52 pm

Thanks for posting that. I have a GL 1800 with a Champion trike kit. When I changed rear tires I saw a lot of oil on the right tire. Had a two month long battle with Champion and my installer also got into the frey. Bottom line is Champion sent me a new breather (vent) and told us drain the oil and explicity do not put more than 32 ounces of oil in the rear.

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Re: How to replace the gear oil in your rear drive

Postby dwight007fchr » Fri May 20, 2011 3:56 pm

Changing the gear oil was on my list of many things to do to my "new" 83 GL1100 Interstate. I ran into a major "situation" when the No. 17 metric box-end wrench slipped off the excessively tight/frozen fill plug. Either it was put on way too tight, or has not been removed in so many years that maybe the threads oxidized. This soft aluminum will strip real easy. I then had to remove the side luggage support frames (another major pain) so I could get to the stripped bolt with a file to attempt to make a new size bolt. I filed and cleaned her up real good, but cant seem to find any No. 16 Metric wrenches (do they make 16s?). The 11/16 standard is too sloppy and would just shear again. Made one last attempt with a vice grip on the shoulder of the bolt, but nothing.....this bolt seems to be welded in place. So, I have drained the little amount of old gear fluid out (maybe half a cup), and am just going to use the vent plug at the top to fill her up. Although, I hope the thick goo will go into this small hole without bubbling up and overflowing due to lack of vent air during the filling. (She was bubbling up and overfilling when I was flushing out with thin oil). I will have to get the factory specs as to how much fluid it takes, and not use the fill plug as a guide. Just checked......5plus ounces or about 150cc gear fluid. Will use the Valveline 75w90 Synpower suggested by Wingman.

Any other suggestions on removal of the filler plug?

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Re: How to replace the gear oil in your rear drive

Postby dwight007fchr » Sun May 22, 2011 9:48 pm

Here is a picture of the trick I used to pour the heavy gear oil into the air vent on the top:

I did this because the fill cap was impossible to remove. The gear oil is so thick that it would just bubble up and spill all over if I were to try using a plain funnel. This syringe will wedge in real tight, and that enabled me to pour in 50cc at a time, and either use a small piece of wire to help the bubbles to come out so the oil would go in, or I could go do some other bike repairs as the oil took its good time to empty from the syringe. Three fills of the 50cc syringe did the trick. Maybe next time I will be able to get the real filler cap off.

My 83 GL1100 has a grease fitting for the drive shaft connection with the rear differential. It appeared to have not been serviced in some time, so I plan to give her a good measure of the appropriate grease (I read the post as to what type to use, but cant recall the name), but wonder if there is a place for the grease to go if I should pack it too tight......does it squeeze out some port? The next time I remove the tire, I will do a full-blown service to that joint.
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Using a medical syringe to pour the thick oil into the air vent top
Using a medical syringe to pour the thick oil into the air vent top

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Re: How to replace the gear oil in your rear drive

Postby WingAdmin » Sun May 22, 2011 10:27 pm

If you have a torch, you might try heating up the drain plug a bit to see if you can get it to come loose (when it's time to change the oil next).

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Re: How to replace the gear oil in your rear drive

Postby andybean » Fri May 27, 2011 3:18 pm

Hey Everyone,

I'm new around here, both to Goldwings and to this forum. Thanks for all the info you've given so far - super helpful!

Last Sunday I bought an 81 Goldwing Interstate w/ just over 40k miles.

After riding it around for a few days, I started to notice some black goo oozing out of the vent on top. At first this worried me, but after reading on this forum and others it sounded like this isn't too uncommon.

So today I tried to change the gear oil following the instructions here, but once I got the drain plug off there were only 3-4 drops of fluid to come out. It's super thick stuff, and it just doesn't seem to be draining. I even tried adding a bit more oil on top of it to kind of flush it out, as some of you have mentioned, but no luck - nothing substantial is coming out of the drain.

Does anyone have any suggestions for me? Is it normal that this stuff would be that thick? It almost feels like grease, but a bit thinner.
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The leak
The leak

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Re: How to replace the gear oil in your rear drive

Postby WingAdmin » Fri May 27, 2011 4:28 pm

andybean wrote:Hey Everyone,

I'm new around here, both to Goldwings and to this forum. Thanks for all the info you've given so far - super helpful!

Last Sunday I bought an 81 Goldwing Interstate w/ just over 40k miles.

After riding it around for a few days, I started to notice some black goo oozing out of the vent on top. At first this worried me, but after reading on this forum and others it sounded like this isn't too uncommon.

So today I tried to change the gear oil following the instructions here, but once I got the drain plug off there were only 3-4 drops of fluid to come out. It's super thick stuff, and it just doesn't seem to be draining. I even tried adding a bit more oil on top of it to kind of flush it out, as some of you have mentioned, but no luck - nothing substantial is coming out of the drain.

Does anyone have any suggestions for me? Is it normal that this stuff would be that thick? It almost feels like grease, but a bit thinner.


That's absolutely not what should be in there. The gear oil that should be in there is thick, similar to engine oil, but it pours easily. Something has gone wrong on your bike - either the wrong gear oil was put in, or something else has happened.

I'd suggest flushing out the entire rear drive with a solvent of some sort (something friendly to seals). My personal preference is brake cleaner, it liquifies the goo instantly, carries it out, and evaporates quickly. You're probably going to need to take the drive off the bike, which is OK - you can lubricate the splines at the same time. Go to the auto store and buy a good ten big cans of brake cleaner, and start hosing it in there through the fill port, vent port, anywhere you can get it. Keep doing it until what comes out isn't black and gooey anymore. Let it dry, reinstall and fill it with the proper amount of the proper gear oil.

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Re: How to replace the gear oil in your rear drive

Postby dwight007fchr » Fri May 27, 2011 8:47 pm

AndyBean, Wingman, etc...........Amazing to see this black good ooozing out.....like a volcanoe about to erupt.

Let me present another opinion here. I just drained and filled mine last week, and did the post above about using the vent hole as a filler spot. I also bought some good moly grease to grease the grease fitting to the front of the vent cap that is oozing this black stuff. As I was pumping grease into the grease fitting, I was wondering where the excess grease would come out if I were to pump too much into it........and I never quite figured that one out. However, after seeing this picture of the black "grease-like" material ooozing out, it makes me wonder if mabye someone pumped a huge amount of grease into this grease fitting, and it leaked past a seal and got directly into the rear drive chamber.

I bet that if you pulled this rascal apart that there would be a seal that has collapsed under the pressure of a gorilla-sized mechanic pumping way too much grease into that fitting.

What do you think Wingman?
dc

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Re: How to replace the gear oil in your rear drive

Postby andybean » Fri May 27, 2011 10:07 pm

Great suggestions DC and Wingman. DC, I've actually had another guy suggest that same theory as well.

Either way it looks like the next step is to take it apart, so I'll get going on that tomorrow. The step by step Wingman posted here (http://goldwingdocs.com/forum/viewtopic.php?f=11&t=73) looks SUPER helpful, so thanks for that!

Thanks you guys. I'll let you know how it goes. Thanks for taking the time to help a newbie out.

Glad to be here,

Andy

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Re: How to replace the gear oil in your rear drive

Postby dwight007fchr » Fri May 27, 2011 10:16 pm

Andy.......Yea, Im a newbie too....only a few months......and Wingman and all the others have helped immensely in the restoration of my 83 GL1100. Let me know what you find out.......as I was wondering where the grease relief was for the excess grease that goes into that grease fitting.

But I guess it was good to have grease back there lubing the differential instead of it being totally dry. Lets hope you dont get the same ooozing action out your Wing's carbs, the exhaust pipes, the radiator, etc........horrible thought!

Will have to call you Jed.......".....and up from tha ground come a bubblin crude, oil that is, black gold, Texas Tea, Goldwing ooze."

dc "Jethro"

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Re: How to replace the gear oil in your rear drive

Postby Pigasus » Wed Aug 10, 2011 7:50 pm

dwight007fchr wrote:Any other suggestions on removal of the filler plug?

I realize you've already got a workaround for this time, but maybe this will be of some value when you're ready to do your maintenance again...

It's not a real common size, but yes, there are 16mm hex tools available for your customized plug. ;) Based on what you've written, I'd find a 6-point 16mm 1/2 drive socket and apply some impact to the filler plug by striking a hammer against the rachet handle while simultaneously trying to turn it out. (An impact wrench might overdo it on those aluminum threads). It's amazing what just a small amount of impact will do for loosening frozen hardware sometimes, and the 6-point socket will be better than a 12-point in that it will hold your hex cap more securely. If that failed, then heat would be my next step. *shrugs*

And I'd definitely apply some anti-seize when I reassembled it!!! :mrgreen:
--Pig

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Re: How to replace the gear oil in your rear drive

Postby dwight007fchr » Wed Aug 10, 2011 9:44 pm

Pigasus......Thanks for your suggestion......That was what I was hoping to try.....get a 16mm socket and file her down to fit perfectly. As you said, the 6 sided would be better.....good point. Then, some tapping may assist in the effort. Definately will put some anti-seize paste on those alminyum threads if I get her off.

In the mean time, at least I have fresh gear lube in her now......glad Honda had the air vent in the top!

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Re: How to replace the gear oil in your rear drive

Postby dkmk81 » Thu Nov 17, 2011 3:44 pm

Hi,

New member here. '82 GL1100.
In reading this "how to" regarding changing the gear oil, it brought
to mind something I learned while working on a British sports car and I
thought I would pass it along. Someone told me, no matter what machine
you are working on, never open the drain plug before you are certain you
can crack open the fill plug. Whatever oil is in there might be old, but it is better
than draining all the oil and not be able to refill and use the machine. Of course you still want to get the
fill plug out and change the oil as soon as you can. I this case, at least it is possible to get
oil in through the vent, but that's not always the case.
Great site, I've learned much already, thanks.

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Re: How to replace the gear oil in your rear drive

Postby WingAdmin » Thu Nov 17, 2011 4:39 pm

dkmk81 wrote:New member here. '82 GL1100.
In reading this "how to" regarding changing the gear oil, it brought
to mind something I learned while working on a British sports car and I
thought I would pass it along. Someone told me, no matter what machine
you are working on, never open the drain plug before you are certain you
can crack open the fill plug. Whatever oil is in there might be old, but it is better
than draining all the oil and not be able to refill and use the machine. Of course you still want to get the
fill plug out and change the oil as soon as you can. I this case, at least it is possible to get
oil in through the vent, but that's not always the case.
Great site, I've learned much already, thanks.


That's an excellent point. I did exactly this when I was a kid, changing the rear differential fluid in my car. I drained it out, only to discover that the fill plug was so seized in place that no tool I had would budge it - and now my only form of transportation was sitting dead in the driveway. It was a long walk to and from the store to buy a big "johnson bar" and some penetrating oil.

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Re: How to replace the gear oil in your rear drive

Postby WingAdmin » Sat Jan 14, 2012 1:41 pm

Randakk has posted a great tip on his site. Apparently, if the rear drive of any year Goldwing (or in fact, any shaft drive motorcycle) has a leak, using Lucas Hub Oil either full strength or 50/50 with gear oil (which is what I would personally be more inclined to do) will work to stop the leak.

Lucas Hub Oil
Lucas Hub Oil


The rear drives are serviceable, but getting them apart to get TO the seals, and then following the very complex procedures to get them back together correctly is beyond a lot of DIY mechanics. This is a simple and quick solution to leaky rear drives.

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Re: How to replace the gear oil in your final drive

Postby hockeystuff54 » Tue Aug 21, 2012 7:10 pm

my guess would be the heavy oil was added to mask another problem such as leaky seal,its similar to adding whole banannas to a car rear end to mask bad gears ,that would be my guess,as that oile was that thick when added to the final drive,its surely not whats supposed to be in there




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