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Final Drive Install Flawed


Roger C

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What's the secret or method for mating the pinion gear spline shaft to the tranny output shaft? I've tried twice today and not sure the 2nd attempt was good. I have the tranny shaft propped up and in the middle of the housing, but not sure the gear spline completely mated. I'm working blind on this so, my friend Michaelr11 is coming to the rescue tomorrow.

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Roger,

 

I did the shaft on my R11S like this, but it has a big boot at the forward U-joint and I could see what it was doing. I don't think you can. But, when you get the U-joint female spline lined up with the male tranny shaft, wiggle it until it mates up and slides home, then bump it with a mallet to engage the snap ring, you'll have a little play in and out and it feels good. This all sounds kinky and reads like a trashy novel but that's how mine worked.

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Hi Roger C - are you trying to mate the short shaft (already attached to the FD) to the long drive shaft, or are you trying to mate the driveshaft itself to the output from the transmission?

 

I think you're trying to put these together - yes?

 

B0003605.png

 

On the RT there is a circlip keeping the driveshaft and transmission output shaft together, and one keeping the short shaft attached to the FD (both pop on/off with a rap from a mallet (as Lowndes says) - there is no such circlip where the shafts meet, so if the shafts slide together enough for you to put the pivot bolts back in (holding the FD to the swingarm), you're good!

 

Putting a rag under the driveshaft, with a tail hanging out the back end of the swingarm so you can pull the rag out, helps, or if you have a friend they can hold the shaft up with a screwdriver/drift inserted through the pivot bolt hole. When I'm doing it by myself with the rag, once I feel the shafts are in contact, I use my left hand to rotate the final drive gears (by turning the brake disc if attached) slightly so they line up and slide together.

 

Don't forget to keep the u-joints phased (as they appear in the pic above).

 

...and if you're trying to work on the other end of the shaft, just ignore me :)

 

 

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Yes, I'm trying to install the final drive by mating the pinion gear splined shaft to the tranny output shaft. Problem one is How do I know what position the U joint for the tranny shaft is. Secondly, How do I keep the pinion shaft splines stationary to mate to the tranny shaft? It keeps wanting to fall to one side. I have the tranny shaft positioned in the center of the housing by propping it on a chunk of foam rubber instead of using a rag. Trying to hold the final drive up and position the pinion knuckle is a real pain for one person. So, working by yourself, how do you hold the final drive up, position the pinion splines, turn the rotor to align the splines and cram the RH pin in place? Also, what's the downside if the knuckles are not parallel?

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Good Morning Roger :)

 

All answers are how I have done this (I only had the FD off our '96RT maybe three times over the years, but we've been traveling with our K1200LT with the same setup for the last year and I don't even want to tell you how many times I've had that FD off :dopeslap: :dopeslap: :dopeslap: )

 

To discern the position of the tranny shaft U joint, you basically look up from the FD end of the swingarm - it's a bit hard to see, but a bright flashlight will help. If the bike is on the floor (as opposed to a lift), you pretty much have to be prone on the floor); I put the bike in neutral so I can rotate the shaft by hand, then pop it into first to keep it there.

 

To slide the whole thing in there, the best way I've seen is to build a jig that holds the whole unit at the proper height from the floor/table top and just slides in. I don't have one of those, so when possible I rest the FD on a box of the appropriate height and use that to hold it up while sliding it forward. When I've not had a box handy, I've sat on my butt behind the bike and sort of balanced the FD on my feet while guiding it with my hands. Moto yoga!

 

I've found this is easiest with the brake disc removed (otherwise when you move the FD around, it tends to roll and turn the pinion shaft messing up your alignment). It's only two bolts and the torque on them isn't much because really the lug bolts for the wheel do the work of holding the disc in place when you are braking.

 

With the disc removed, and the FD on it's just right box, use your left hand to hold the FD where the brake disc was mounted - it should be tight enough to not turn on its own, but loose enough that you can turn it a bit yourself to align the splines (put a couple of wheel bolts in there to make it easier if you like).

37191614954_22ec291c57_z.jpg

 

Slide it forward into position. I keep my right hand around the front right side of the FD so I can hold the shaft up with my fingers until it mates, and then once it mates I reach over to the pivot bolt and slide it in. Then the other pivot bolt just enough to hold it there... and then I follow the steps I can't remember off the top of my head for properly installing the pivot bolts.

 

 

(In reality at this point, mostly, I realize of the bearings has fallen out, or I turned the shaft, or - this was the last time - I forgot to put the boot back on, and then I do it all again!).

 

36556888673_ddd20313e7_z.jpg

 

edit to add:

I don't really know that this is true, but what I've been told is that proper phasing will help reduce vibration.

Edited by szurszewski
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"edit to add:

I don't really know that this is true, but what I've been told is that proper phasing will help reduce vibration."

 

I was unable to discern the position of the U joint on the front end of the drive shaft. I even wasted time trying to use my "Super eyes" snake light but that didn't help either. So, I have the tranny in 1st gear. We will proceed to install the final drive. If there is vibration, maybe it will counterbalance the vibration of the engine. Or, if Michael has a better idea for aligning the U joint knuckle and the pinion gear knuckle, we will try that. Nice pics, btw.

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One of the upsides of having eaten the bearings on our FD three or four times in the last year is that I have LOTS of pictures of the back of our rig in various states of disassembly. (We're running a very overloaded sidecar and towing a trailer, sometimes on roads we probably shouldn't even have the bike on by itself - the big bearing in the FD doesn't seem to be a fan of this.)

 

Sorry you couldn't see the front U-joint - I find it hard to see as well but have been able, when turning it slowly with a good light shining up there, to see when the knuckles come around. Good luck getting it all back together today!

josh

 

 

Edited by szurszewski
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I put the final drive on a floor jack and wheel it up to the swingarm. I also use tiny zip ties to hold the bearings in place while I'm wrestling with the alignment. I've had some success with lifting the final drive up with a screwdriver to aid in lining the ends up. You can also mark the driveshaft in some manner to help you line up the two halves.

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It just took an experienced pair of eyes and hands and Michaelr11 had my final drive aligned and engaged in less than 5 minutes, whereas I had struggled with it for what seemed like hours. The cardboard box was a great idea as it allowed him to be able to regrasp the unit for better control. Got everything all buttoned up and hope to take a test ride later this week, depending on mow my leg feels.

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I found it very helpful to phase the drive shaft while out of the swingarm, then MARK the mid-shaft splines so that the marks can be seen end-on, from behind, while installing. Paint and marker pens will not be there when you need 'em. Use a file or center-punch to index mark (same with the clutch components).

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I found it very helpful to phase the drive shaft while out of the swingarm, then MARK the mid-shaft splines so that the marks can be seen end-on, from behind, while installing. Paint and marker pens will not be there when you need 'em. Use a file or center-punch to index mark (same with the clutch components).

 

My drive shaft is attached to the transmission output shaft. If I were to pull hard on the shaft, that might release it from the knuckle, in order to see the position it is in. But then I have to somehow reattach the shaft to the knuckle buried up in the drive shaft housing. I can't see the knuckle position by looking into the drive shaft housing. How critical is phasing the knuckles?

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I found it very helpful to phase the drive shaft while out of the swingarm, then MARK the mid-shaft splines so that the marks can be seen end-on, from behind, while installing. Paint and marker pens will not be there when you need 'em. Use a file or center-punch to index mark (same with the clutch components).

 

My drive shaft is attached to the transmission output shaft. If I were to pull hard on the shaft, that might release it from the knuckle, in order to see the position it is in. But then I have to somehow reattach the shaft to the knuckle buried up in the drive shaft housing. I can't see the knuckle position by looking into the drive shaft housing. How critical is phasing the knuckles?

 

Morning Roger

 

If you pull on that drive shaft from the rear it will probably come apart mid shaft (it has a 2 piece shaft). (those a real bugger to get back together when inside the swing arm)

 

The U joint phasing isn't super critical as the U joints don't operate at the same angles front & rear (they only cancel each other out when operating at close to same working angles). In fact the BMW service manual doesn't even address drive shaft U joint phasing.

 

They should be phased when re-assembling (just because) but it makes little if any difference in down-the-road vibration or shudder.

 

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My rebuilt final drive was installed without regard for the upper shaft knuckle position. My wheel turns freely and there is no noise so, I will not worry about phasing.

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