R75/7- driveshaft bolt stripped!! why?

[herman maire]

Thanks for looking. I am trying to figure out why the bolt stripped on my driveshaft coupling when I tried to torque it to spec (170-180ft/lbs.)

Is this the correct torque figure?

This was supposed to be a 2 minute job.... all I had to do was torque the coupling bolt on the driveshaft and install my shinny freshly painted swing arm .

It was not to be, it went from worse to worse.....

After the bolt stripped, it was impossible to remove the nut since all it would do is spin and would not catch the last 2 treads on the driveshaft.

I bring it to a machine shop, I tell them the problem, they say no problem. I say cool.

While I am busy working on something else I get back to the shop and they hand me the shaft in 2 pieces.... I say WTF did you do.

Oh, we had to torch the nut off also cutting the treaded section of the driveshaft off. Its amazing how stupid people are.

So, if anybody has a driveshaft that would work with a R75/7.... please PM info and price.

Thanks

[jbcaddy]

that is a sad tale so sorry

[pommie john]

I haven't got my manual in front of me, but 170 ft pounds seems a hell of a lot.

[pommie john]

As you were! My manual says that's the right torque.

[airheadDavey]

There is now way they are 170ftlbs. I think you may have misread the manual. The center nut on the back of the output shaft I believe is that tq spec. I dont have the manual in front of me to give you the proper specs on the bolts. Sorry that happened to you and I feel your pain.

[airheadDavey]

Originally Posted by pommie john

As you were! My manual says that's the right torque.

Are you sure its not 170 inch pounds?

[noman]

from my r75/6 bmw repair manual:

hex nut on coupling bell housng 173.5 -188 ft-lbs
twelve-sided bolt 17.3 - 18.8ft-lbs

may not be the same as r75/7

[herman maire]

Thanks for the replys.

the bolt I had trouble with is not the transmission output shaft bolt.

In the link you have to select driveshaft and it is #7 in the diagram http://www.maxbmwmotorcycles.com/fic...7&rnd=03252011 .

Still looking for a driveshaft in good condition if anybody has one.

[Bill Harris]

Folks, I think he's talking about Nut #7 that holds on Flange #6.



I don't have the /7 spec with me, but 170 ft-lbs sounds correct-ish.

[herman maire]

Originally Posted by Bill Harris

Folks, I think he's talking about Nut #7 that holds on Flange #6.



I don't have the /7 spec with me, but 170 ft-lbs sounds correct-ish.

Bill,

Thanks for that.... yes it is indeed #7.

[wirewrkr]

Just bad luck, that's all.
Move forward, get another shaft and fix it.
Most used shafts have notchiness in the joint.
It's just the way it is, don't freak out when you find a used one that way.
Some is okay, Too much is not.

[Boon Booni]

Did you torque it with dry or oiled threads?

[PaulRS]

For the /7 the manual states a slightly lower spec, around 150 Lb-Ft (converted from Nm).
But that wouldn't strip the threads, imho.

Manual says nothing about oiling, so it should go on dry.

Just bad luck, I think.

Paul.

[bmwrench]

The spec is/was 170 lbs/ft, but I haven't put that much torque on one in years. Go to 150 with a drop of red Loctite on the threads.

[Bill Harris]

And the coupling is a taper-fit so make for absolutely certain that BOTH parts of the taper (inner & outer) are oil-free-- clean with acetone or brake cleaner if need-be.