Why Lord...why? (another input kaput)

R69S · R69S's Garage

So...I had the dreaded input shaft failure last summer. Thinking alignment was the most likely culprit, I cheap'd out and slapped in a low mileage trans and clutch assm. from BeemerBoneyard. Not exactly cheap as it cost me $2k by the time I was done.

I heard it clicking (more like ticking : P ) for the last few weeks. It completely shred last night while down shifting on the off ramp. Local dealer wants $1k for labor and $1k for parts. I like my bike but I am sick of sitting on a time bomb. The posts I have seen still don't really have a pinpoint on how to fix this once and for all. It seems misalignment and possibly metal strength are subject to questioning but no silver bullet has been found. Just venting really, thanks for reading.

roger albert · 04-10-2009, 03:11 PM

Yikes. Sorry to hear it. That does suck. Vent away.
A used trans and and clutch assy mean you don't get much valuable data, as you didn't have a clean starting point. The other reason there is no silver bullet is that there are differing reasons, and combinations of reasons. I'd sure look at alignment when things went back together, but that not easy. Need to be a machinist and a motor builder (crank sitting not same height as crank spinning, etc) Not an easy job. Good luck!

bill pierce · 04-10-2009, 04:45 PM

Really sorry to hear about you having this happen 2x.

How many miles between failures?

R69S · R69S's Garage

Quote:

Originally Posted by bill pierce

Really sorry to hear about you having this happen 2x.

How many miles between failures?

Only about 2k. Still wondering what went wrong...misalignment of clutch maybe..? The replacement trans / clutch only had 14k on it. I am hoping against hope that it may be a broken drive shaft as the sound seems a little far back.

bill pierce · 04-10-2009, 07:35 PM

Quote:

Originally Posted by R69S

Only about 2k. Still wondering what went wrong...misalignment of clutch maybe..? The replacement trans / clutch only had 14k on it. I am hoping against hope that it may be a broken drive shaft as the sound seems a little far back.

With only 2k it may be something else. Did you see this thread?
Clutch splines

SergioK · 04-10-2009, 07:59 PM

Man that sux! Twice in less than a year. I'd be pulling my hair out. At least my two failures were two years apart.

R69S · R69S's Garage

Hurray, it's not the input shaft! It was sounding a little further back in the drive line so I peeled the rubber boot back and sure enough the trans exit spine and drive shaft are detached. Not sure what would make the drive shaft pop off like that but I should be able to fix this without pulling the transmission (knock on wood).

Is there some type of retaining clip that holds the drive shaft on or is it just held on by friction and lack of anywhere else to go? The drive shaft collapsed maybe?

I imaging I will have to remove the swing arm to repair it. The BMW manual says I need BMW tools:

Using pull rod, BMW No. 00 8 581, and impact
weight, BMWNo. 00 8 582, pull out the swinging
arm fixed bearing stud bolt.

I did a little searching but am unsure what tools can be substituted from the local Sears. I though some one said you just need to make sure you have a 12mm allen wrench...I'll keep searching.

wswartzwel · 04-13-2009, 10:19 AM

There is a retainer ring in the yoke... (looks like a wedding band that has been cut) the output shaft has a groove in the spline. You force the female yoke forward until that ring snaps into the groove.

SergioK · 04-13-2009, 11:52 AM

Quote:

Originally Posted by wswartzwel

You force the female yoke forward until that ring snaps into the groove.

I will quote you on this one day.

wswartzwel · 04-13-2009, 12:06 PM

roger albert · 04-13-2009, 12:13 PM

Ha,

But seriously, I don't know how you get enough longitudinal play in there allow it to back out anyway. Wouldn't have thought that was an option. Learn something new every day.

wswartzwel · 04-13-2009, 12:25 PM

The drive shaft has a telescoping spline in the middle, so there is plenty of space for the yoke to come off the output shaft of the tranny, or the input shaft of the final drive... Usually only happens if a previous mechanic had it apart and didn't seat the retainer.

R69S · R69S's Garage

Quote:

Originally Posted by wswartzwel

The drive shaft has a telescoping spline in the middle, so there is plenty of space for the yoke to come off the output shaft of the tranny, or the input shaft of the final drive... Usually only happens if a previous mechanic had it apart and didn't seat the retainer.

That makes seance as the transmission was replaced about 2k miles ago. If it's not too difficult I would just like to re-attach it at home.

Do you think I would have to back-off the swing arm a bit to get at it for re-attachment?

wswartzwel · 04-13-2009, 05:27 PM

It takes a good bit of force to get the yoke pushed all the way up the shaft. You might be able to pry it up somehow through the small opening behind the tranny and in front of the swing arm. It would be better to pull things apart though, and properly inspect the parts for damage.

roger albert · 04-13-2009, 07:38 PM

Man, I've had those apart a ton of times, but never envisioned a scenario where all the splines could collapse enough to allow the other set to overextend that far. Looking at one that was going back together today, I can now see it being theoretically possible (which is obviously is) but I'd have bet large against it. Glad I didn't. Always something new to learn.

R69S · R69S's Garage

Quote:

Originally Posted by wswartzwel

It takes a good bit of force to get the yoke pushed all the way up the shaft. You might be able to pry it up somehow through the small opening behind the tranny and in front of the swing arm. It would be better to pull things apart though, and properly inspect the parts for damage.

Took another look at it tonight. I can't get at it with the small opening where the boot is. I need to pop off the round plastic cover / swing arm bolt to push it forward first. I don't have the special tool I previously mentioned. Can I just use a basic slide hammer? It wouldn't be horrible if a new tool made it's way home to my garage

. On a good note, the output splines look to be in good shape.

flatbutt · 04-14-2009, 06:47 AM

R69S, I remember ol' Razorback really grunting on this aspect of the job. Bill didn't you use a crow bar or pry bar that was really really long?

roger albert · 04-14-2009, 06:57 AM

1 or 2 prybars or screwdrivers will do it fine.
Some come of easy, and some do need the grunting.

wswartzwel · 04-14-2009, 07:03 AM

Quote:

Originally Posted by flatbutt

R69S, I remember ol' Razorback really grunting on this aspect of the job. Bill didn't you use a crow bar or pry bar that was really really long?

Tom, I had the frame unbolted and back an inch or two, when we did your input shaft /clutch R&R. There is not much room with the frame assembled to the engine.

Sure you can pry it off with a couple screwdrivers.... but he is trying to put it back on. Getting behind the yoke, and being able to center it enough to force the ring over the end of the shaft will take some finesse with everything bolted together.

Try putting some grease on the end of the shaft to help thing slide better.

RBMann · 04-14-2009, 11:00 AM

I was in the same position and could not get the driveshaft reconnected until the swing arm was removed. Since the FD was already off it was not that much more work.