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Discussion Starter #1 (Edited)
I just picked up an '02 VN750, introduced my-self in the newbie section several days or so ago. Thank you so much for the kind words.

I'm preparing to lube the spline and was wondering why the Moly 60? Wouldn't a high temp bearing or gear grease work as well? Would Chevron Ultra-Duty EP NLGI2 grease work? Just asking, I'm curious that's all.

In addition I had at one time an '89 VN750 that I bought new and sold 5 1/2 years later with 46,500 miles on the clock. Due to ignorance on my part never lubed the spline, never had a problem with it. Just lucky I guess.

Thanks for the info gang. And again, thanks for all the great write ups on the repairs and maintenance required to keep what I feel is a terrific bike on the road.

Rusty
 

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Moly is used because it stays on the gear teeth even when the carrier grease has been shot out to the sides of the casing
 

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In addition I had at one time an '89 VN750 that I bought new and sold 5 1/2 years later with 46,500 miles on the clock. Due to ignorance on my part never lubed the spline, never had a problem with it. Just lucky I guess.
Wow. Kinda passed off a ticking bomb there. Even moly lubed splines can tear up after 46,500 miles.

My only hope is you sold the bike to the chap here that made his own airfilter....;)
 

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Moly is used because it stays on the gear teeth even when the carrier grease has been shot out to the sides of the casing
Swagman is right about the moly continuing to lubricate even when the carrier grease is gone.
The explanation given to me is that molybdenum molecules conditions the metal by actually penetrating the outer layer of metal molecules.

I`m going to take some flack for this, but I have a tube of CV joint grease that I am going to use for my spline lube soon. I`m sure it has moly in it, but don`t know what percentage. (I have found a couple of commercial greases (including John Deere) that contain moly, but only 3%, not 60% like the Honda Moly Paste.)
I will need a new rear tire in a few thousand miles, so it will be a chance then to check on the splines and CV joint lube again, well before the recommended 10 k miles spline lube.
 

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HAWK
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Any grease will work its just that cheeper grease wears out faster so You have to do more often. If there was a fitting so you can just pump in more no problem. Good thing is it only take a table spoon or so. A tube of Honda Molly will last you along time.
Redo every rear tire change just to be safe.
 

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Any grease will work its just that cheeper grease wears out faster so You have to do more often. If there was a fitting so you can just pump in more no problem. Good thing is it only take a table spoon or so. A tube of Honda Molly will last you along time.
Redo every rear tire change just to be safe.

OL Hoss said
I`m going to take some flack for this, but I have a tube of CV joint grease that I am going to use for my spline lube soon. I`m sure it has moly in it, but don`t know what percentage.
I will help you out Gordon,I lubed mine with waterproof High pressure bearing grease every time I changed the rear tire on mine and always had to clean old grease out of the splines,I think Chad is right,it is how often you lube them ,if you did a good job and got everything coated good as often as you should.

Mine looked like new the first time and the last time I did the job,And ask those who have ridden with me, my bikes get launched hard and if they were gonna strip my big butt and heavy right hand would do 'em in.Wib714 will vouch for me he has seen me hittin' it hard on the 1500,and it isn't treated any easier than any other bike I have owned.
 

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Properly lubed splines should easily outlast the engine, they should outlast 2 engines. For splines to last 46,000 miles without grease is almost unheard of on the Vulcan 750, but not that uncommon on many other bikes. You must of been one of the few lucky ones that got their splines lubed at the factory. I waited until 12,000 miles on my bought new '93 to lube the splines, and found them dry, with some damage, though no rust. They had started to chew themselves up (IMO, they should be made of MUCH harder metal) I packed them with grease every 10,000 miles after that, and they survived past 80,000 miles. Keeping them lubed seemed to pretty much stop the wear/damage, they didn't look much worse the last time I lubed them than they did the first.

I have used that 3% wheel bearing grease, and it worked just fine. But, I always relubed them every 10,000 miles without fail. The moly paste should last a lot longer. I am still doing mine at 10,000 miles, even with Guard Dog 570 73% moly paste, but that's most likely overkill. I am actually planning on waiting until my rear tire wears out to do it again, which will be around 18,000 miles. I packed everything with GD 570 last time, used about $20 worth of it.

Though it is usually the rear splines that fail, I still believe the front splines (in the U joint and on the output shaft) should be lubed too. This is the hardest part, as you have very little working room. Some say these are not as important as the rear ones, but I believe anywhere they is movement there should be lubricant.

IMO, from experience with an old '85 Goldwing with nearly 100,000 miles on it, that still had perfect splines, I believe part of the problem, if not most of it, with the Vulcan 750 splines, lies with the design of the splines themselves. The GW had much larger shafts, with much beefier splines. They were a lot deeper and wider, both the high points and low points. Each spline was much thicker than on the Vulcan. The GW splines looked a lot like the input shaft on a car transmission, while the Vulcan splines are a lot flimsier looking. The GW splines also fit together fairly tightly, with noticeably less play than the ones on the Vulcan.
 

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OL Hoss said


I will help you out Gordon,I lubed mine with waterproof High pressure bearing grease every time I changed the rear tire on mine and always had to clean old grease out of the splines,I think Chad is right,it is how often you lube them ,if you did a good job and got everything coated good as often as you should.

Mine looked like new the first time and the last time I did the job,And ask those who have ridden with me, my bikes get launched hard and if they were gonna strip my big butt and heavy right hand would do 'em in.Wib714 will vouch for me he has seen me hittin' it hard on the 1500,and it isn't treated any easier than any other bike I have owned.
I'll vouch for you, seen him stand it up a little on wet pavement! figure that one out?
 

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Though it is usually the rear splines that fail, I still believe the front splines (in the U joint and on the output shaft) should be lubed too. This is the hardest part, as you have very little working room. Some say these are not as important as the rear ones, but I believe anywhere they is movement there should be lubricant.
Jerry, I don`t have anywhere near the wrenching experience you have, and practically no hands experience on motorcycles. I agree with you that anywhere there is movement there should be lubricant. Any type of drive shaft splines in my opinion should have little or no rotational free play or "slop". I believe the vn splines in new condition meet this criterion.

The rear spline connection between the drive shaft and the final drive are designed to slide back and forth, or "pump" in and out to compensate for up and down movement of the suspension and swingarm. This creates heat and wear potential, making proper and regular service and lubrication of that connection critical. However the expansion spring inside the space on the drive shaft/final drive coupling would tend to keep the drive shaft pushed tight against middle drive on the back of the engine. In my mind this equates to a minimum of fore and aft movement on the front drive shaft splines, and far less potential for wear than the rear splines on the same shaft.

I would check them the first time I serviced the bike, but would be comfortable greasing them with a white spray grease through a small red straw if I couldn`t get in with a popsicle stick or similar, to get Moly60 or Guard Dog 73% on them.

When I do my spline lube, it will be interesting to me to see the difference between the vn splines and automotive drive splines that I am somewhat familiar with.
 

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I am going to agree with Jerry on this one ,the splines on the 750 are a bit spindly compared to a lot of other rides,and the front splines do need a good coat of grease on them to ,it is not a big deal on the 750 to lube the front splines while you are at it.There is some movement there although you are correct in saying,Ol Hoss, there isn't as much as in the back.
 

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I would certainly expect the splines on a Goldwing to be much beefier than those on a VN750. The GW is a much bigger bike. The VN750 is one of the smallest shaft drive bikes so I would also expect that the splines to "look" more flimsy than many other bikes and I certainly don't think comparable at all to automotive splines (other than comparing design concepts out of interest.) I think the design is fine and as has been already said, if properly lubed will long outlast the life of the bike.

How much sliding action does the spline have? I was curious so the last time I lubed my splines I tried to measure the movement of the drive shaft (spline coupling) with regard to the swingarm. With the shocks removed I clamped a flat bar across the flange at the rear of the swingarm. Using a small ruler I tried to measure any movement between the shaft coupling and the surface if the flange as I swung the swingarm through it's full range of motion. I could not detect any movement. I could not even feel any movement. I believe that any movement had to be much less than 1/32".

I too had expected there to be significant movement or pumping action at the rear spline as the rear wheel moved up and down, but this is not the case. The center-line of the front U-joint is aligned with the swingarm pivot point to eliminate the drive shaft spline sliding motion. Of course the design must account for some movement caused by thermal expansion and normal wear as well as design and manufacturing tolerances.

A more significant source of wear would occur if the shaft coupling and and the spline on the final drive were not perfectly aligned (on the same center line.) Every shaft revolution would result in a very slight movement between the coupling and the spline - like a mini-u-joint. This could be caused by the final drive not being properly bolted to the swingarm flange for example. Take care when re-assembling the final drive that there in no foreign material under the flange and that the bolts are properly torqued.
 

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I would certainly expect the splines on a Goldwing to be much beefier than those on a VN750. The GW is a much bigger bike. The VN750 is one of the smallest shaft drive bikes so I would also expect that the splines to "look" more flimsy than many other bikes and I certainly don't think comparable at all to automotive splines (other than comparing design concepts out of interest.) I think the design is fine and as has been already said, if properly lubed will long outlast the life of the bike.

How much sliding action does the spline have? I was curious so the last time I lubed my splines I tried to measure the movement of the drive shaft (spline coupling) with regard to the swingarm. With the shocks removed I clamped a flat bar across the flange at the rear of the swingarm. Using a small ruler I tried to measure any movement between the shaft coupling and the surface if the flange as I swung the swingarm through it's full range of motion. I could not detect any movement. I could not even feel any movement. I believe that any movement had to be much less than 1/32".

I too had expected there to be significant movement or pumping action at the rear spline as the rear wheel moved up and down, but this is not the case. The center-line of the front U-joint is aligned with the swingarm pivot point to eliminate the drive shaft spline sliding motion. Of course the design must account for some movement caused by thermal expansion and normal wear as well as design and manufacturing tolerances.

A more significant source of wear would occur if the shaft coupling and and the spline on the final drive were not perfectly aligned (on the same center line.) Every shaft revolution would result in a very slight movement between the coupling and the spline - like a mini-u-joint. This could be caused by the final drive not being properly bolted to the swingarm flange for example. Take care when re-assembling the final drive that there in no foreign material under the flange and that the bolts are properly torqued.
Thanks for sharing the results of your research Paul. Nothing educates so much as first hand experience. I would have expected more fore and aft movement of the driveshaft coupling to the pinion shaft on the final drive.

About 30 years ago I drove a single rear axle GMC truck at work with a capacity of about 7 ton as I recall. I don`t remember the series model number, but it was a gas pot not a diesel. It had a 2 or 3 piece driveshaft with extra U-joints and "pillow bearings" bolted to the frame to support the driveshaft at these flexible joints.

Each joint also had spline coupling about 4" long IIRC. These splines had a grease zerk to allow frequent servicing. I know these spline couplings moved back and forth because I hit the brakes hard one time and the long rear driveshaft pulled right out of the female coupling, and tried to polevault the back end into the air when the forward end hit the ground. Turned out the truck had a loose or broken U-bolt holding the axle to the frame on one side.

Not sure how much movement fore and aft they had when working properly, but there must have been some because I would see some lubricant pumped out the back of the coupling during the pre-trip inspection the next day after being greased.
 

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Gordon, Must have been quite an exciting experience when your truck drive shaft dropped. That got me thinking about the geometry of the suspension vs the driveshaft. (I found this an interesting mental exercise.) If we assume the truck frame, rear suspension to the axle and the drive shaft form a right triangle with the drive shaft as the hypotenuse. Using an estimated length of 8 ft for the frame (from above the u-joint to just above the axle) and 2 ft for the rear suspension (from the frame to the axle) the drive shaft will be approximately 99 inches long. Using basic geometry, If the rear springs are compressed by 2 inches the length for the drive shaft changes by about 1/2 inch. While the numbers may not be totally accurate, the geometry shows that indeed there will be significant sliding movement of the driveshaft spline and coupling as the truck bounces down the road.

The VN750 shaft u-joint and swingarm have the same pivot point. As the rear suspension compresses, they move through an arc. The distance between the end of the drive shaft coupling and the flange of the swingarm remain at a constant distance and in theory there should be no sliding movement between the spline and the coupling.
 

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Properly lubed splines should easily outlast the engine, they should outlast 2 engines.....I packed them with grease every 10,000 miles after that, and they survived past 80,000 miles.
I purchased my '03 VN750 with 39K on the odometer in the summer of 2016; current odometer reading is 42K. I've read a lot here on the spline lube procedure and its importance. It's something I've "meant" to get done, but simply haven't.

One question I've had all along is how often the spline should be lubed. VN750Rider/Jerry's comment me really wondering now. If a properly lubed spline should "easily outlast the engine, they should outlast 2 engines" then why grease them "every 10,000 miles after that"? Not being a smart-ass, but just trying to educate myself.

Should it be done every [x] miles...every rear tire change...etc??? Thanks guys!

Don't forget to pause to remember and reflect on our freedoms this Memorial Day. All gave some. Some gave all.
 

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A properly greased spline should outlast the motor, the key phrase is "properly greased"
Even using high moly content grease (recommended) the sheer pressure and heat the splines endure will eventually burn, melt and wear that lube out. So checking them every 10,000 miles is a good idea. (LESS if you are not using the moly grease we recommend here... regular bearing grease might not last that long)
 

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Thought this would be in the maint. schedule, but I don't see it. The download owner's manual is incomplete.

Cleaned and greased with every rear tire change should be good.

Thought I saw every 8000 miles somewhere, but not finding that now.
 

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Is it possible to estimate the state of the shaft by putting the bike on the center stand, putting it in gear, and measuring how much play is in the rear wheel?

My bike just rolled over 19k and I don't know if it's ever been lubed. I was planning on waiting to the end of season to do this. At the rate I'm adding miles, I might hit 25k by then.
 

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Is it possible to estimate the state of the shaft by putting the bike on the center stand, putting it in gear, and measuring how much play is in the rear wheel?

My bike just rolled over 19k and I don't know if it's ever been lubed. I was planning on waiting to the end of season to do this. At the rate I'm adding miles, I might hit 25k by then.
I've tried that, but it's probably only good to see if the splines are completely stripped and slipping.
 

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My '03 was completely dry and rusty when I pulled the shaft the first time last year. Luckily it was a low mileage bike, and I got to it before any serious damage was done. I wouldn't wait to lube the splines. It's pretty easy to do.

GDI
 
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