Installing RotoFlex couplings

[m750rider]

Its been many years since I last replaced the donuts on my 69 S4 and after removing them when one broke (they had been in probably 30 years with many miles so no complaints) I am now in the middle of going back in with the new ones.

The left side went in easy enough by putting on both inboard and outboard donuts to the output shaft and to the brake disc, then fitting the intermediate shaft to the outboard donut, then working it into place one bolt at a time on the inboard side.

The right side is being more difficult, seemingly with less room to move the intermediate shaft into place. The donuts are assembled correctly with the high boss of the donut against the shaft and the low boss against the bolt heads.

Is it possible that the output shaft from the differential slid outward slightly when I removed the donuts and intermediate shaft on that side? There should be a circlip (haven't looked) that keeps the axle in place but is there any movement possible?

If so can I just tap it inward?

The workshop manual says to "carry on with the remainder of the replacement procedure by reversing the removal instructions." Lots of help there.

Like I said I did this once a long time ago so I remember very little about exactly how to do it.

The car is not on a lift, but I can compress the suspension as needed to line up the intermediate shaft to the output shaft.

Any advice would be helpful.

Thanks

Bob

45/8842
1969 S4 SE

[rgh0]

The diff should be centred between the rear suspension hubs if not you need to understand why not. I would measure it up to see if its equal both side, if not this could be cause of your difficulty

Yes the diff output shafts are secured into the diff with circlips - or should be so should not move

As you say you need to jack the suspension to raise it to align the donuts with the flanges so the bolts can be inserted

cheers
Rohan

[Lotusian]

You say that a doughnut broke.
Might this have done some damage in the process, possibly bending the “ears“ of the intermediate shaft or the output shaft (I assume it was the inner one which broke)?
Alternatively, since the doughnuts were 30 years old, might the diff mountings be even older and deteriorated to a point where they allow the diff to move across the chassis?
Ian

[billwill]

The following topic with many photos describes how I fitted new doughnuts back in 2007.

To solve your problem, I disconnected the hub from the A frame so that it could be swung out and back to then fit easily to the outer doughnut.

viewtopic.php?f=37&t=16456&hilit=doughnuts

[m750rider]

Thank you all for the advice and willingness to help out.

The problem was the differential unit was not centered - why I don't know or how it got that way- but I was able to move it into the correct position, and doing so freed up space to fit the right hand side intermediate shaft to the inner donut. Now I just need to torque everything properly and put the wheels back on, and I'll be back on the road. Spring is almost here and it's the best time to ride.

Thanks Rohan.

Bob

45/8842
1969 S4 SE

[Lotusian]

I don’t want to sound too alarmist, but the diff shouldn’t move from side to side.
Are you sure there isn’t something wrong with the top mounts?
Ian

[m750rider]

I checked, top mounts, and lower, are good.