V11 drive shaft play

[Pressureangle]

51 minutes ago, motortouring said:

Well, I did a little inspection.

It is a bit dificult to see, but I tried to put the center of the picture on a somewhat deformed part of the splines. It looks like the drive shaft was mounted to short on the splines and then the bolts were forced through.

It is difficult to see other wear on the splines of the pinion. 

I think, I wil try to find a drive axle first to replace the existing. From there I go further.

I'm not seeing anything problematic. I installed my own yesterday, and I can say with confidence that there is absolutely no way to force the bolts past the splines without being in the appropriate relief. 
My rear drive came to me partially disassembled, or had been, in a box. I replaced the main bearings and cleaned everything, but did not replace the pinion bearings. I studied the play in the pinion very carefully, as this thread had been posted by then. Reviewing the internal structure of the bearing arrangement, and an hour on the bench testing adjustment, that there is *no way* to assemble this box and have zero play, either radially or axially. That is a function of the front, or thrust bearing, which appears to be an angular thrust race ball bearing but not one with very tight tolerance such as in a machine tool spindle. So by the time the adjustment is tight enough to stop play, the assembly is so tight it's hard to move and would self-destruct. I adjusted mine about one hole on the retainer plate looser than the point at which I could feel the rotational resistance change. That left me with just enough play in both directions that in any other shaft I would be concerned that the bearings were shot. But that seems to be the way it is, and likes to be. 
To the point of having too much play, well, it seems anecdotally that they don't much care; these are spiral bevel gears, not true hypoid gears, so they tolerate axial movement far more than hypoid will. And, because the thrust surfaces don't change their orientation under load, the bearings are unaffected. I would, for my own peace of mind, tighten the adjuster up until I had (shame on me for not actually measuring my own) .020" to .050" of movement. <shrug> 

 

And thanks to @nuevototem for showing me that those spacers go under the joint cover, I was going to complain about how difficult it was to install the rear joint bolts without unbolting the cover. 
I'll get them in at the next tire change lol

[motortouring]

@Pressureangle

Many thanks for this explanation.

The play at the pignon wheel/axle in its housing is neglectable in my bevelbox. My concern is the play at the splines of the pignon axle where the drive axle is fitted. There is approx. 2mm axial play. The drive axle spline end moves over the pignon axle splines.

In my 2002 V11Sport, this is tightly fixed.

[Pressureangle]

4 minutes ago, motortouring said:

@Pressureangle

Many thanks for this explanation.

The play at the pignon wheel/axle in its housing is neglectable in my bevelbox. My concern is the play at the splines of the pignon axle where the drive axle is fitted. There is approx. 2mm axial play. The drive axle spline end moves over the pignon axle splines.

In my 2002 V11Sport, this is tightly fixed.

To confirm, by axial play you mean 'in and out' along the splines not across them, yes? After torquing the bolts properly? 
In that case, as a matter of interest, I'd test the fit of both yokes on opposite ends. If the yoke is worn, the front yoke will be tight on the rear splines and the rear yoke loose on the trans end. If the spline shaft is worn, the front yoke will have play on it and the rear will be tight on the trans end. 
Axial, or in-and-out play is far less concerning than radial or across-the-spline looseness and may be resolved by increasing fastener torque. 
FWIW I'm not a fan of 'lubricating' non-slip splines as the yoke is intended to grip them tightly. The real issue over time is rust, so I just give the yoke and shaft splines a hit of Cosmoline, which isn't much of a lubricant and never needs re-application. 

[motortouring]

Yes, the play that I talk about is front to rear. In the rotational direction the splines do what they should do. Tightening the bolds does not really have effect for some reason.

I checked the other end of the drive shaft ( the gearbox side) also 2mm play front to rear.

Anyway, step by step to a final solution. I will first look for a new drive shaft.

Edited October 25 by motortouring

[docc]

Agreed, the yokes should clamp tight to the splined shafts on both ends. Perhaps the fasteners, or the threads in the yokes have been compromised/ "cross-threaded?"

This happened to mine and "may have been" contributory to failure . . .

Rear:

Then later, the front:

[Pressureangle]

Yes, for whatever reason it's very easy to cross-thread these bolts. I suspect without measuring that MG set an angle to the thread centerline and bolt head seat countersink, so that they are perfectly perpendicular when torqued, meaning the bolt hole is not parallel to the bolt threads when you're starting the fastener. I had to chase the threads on my drive end, and found the original bolt that lost thread material into that hole proving it was started poorly at least once. New bolts and a tap chase for sure. I don't recall the factory spec, I torqued mine to 34 lbs-ft and all seems well. 

[motortouring]

These are really great tips, guys!! I noticed indeed that in my '99 the bolds were some 1mm less deep into the holes then in the '02.

This is an easy thing to check first.

[gstallons]

A man wants to be absolutely , positively , certainly SURE before installing a bolt in anything. This is an example of when it has to be right !

Edited October 25 by gstallons
spelling error

[Lucky Phil]

6 hours ago, Pressureangle said:

Yes, for whatever reason it's very easy to cross-thread these bolts. I suspect without measuring that MG set an angle to the thread centerline and bolt head seat countersink, so that they are perfectly perpendicular when torqued, meaning the bolt hole is not parallel to the bolt threads when you're starting the fastener. I had to chase the threads on my drive end, and found the original bolt that lost thread material into that hole proving it was started poorly at least once. New bolts and a tap chase for sure. I don't recall the factory spec, I torqued mine to 34 lbs-ft and all seems well. 

The reason they are easily cross threaded is because the lead of the threads is partially intersected/interrupted by the shaft splines.

Phil 

[Pressureangle]

44 minutes ago, Lucky Phil said:

The reason they are easily cross threaded is because the lead of the threads is partially intersected/interrupted by the shaft splines.

Phil 

So it is, and quite obviously in Docc's broken yoke. Missed that.

[nuevototem]

Hi all,

Just an update from my side. I take my tool and check that both bolts are tight at 25nm and they are ok. There is still play but leave it like that... is ok? do I have to test to tight more nm? like 30nm or 35nm till there is no play? Any suggestions?

[docc]

I thought we had determined the bolts are 10mm and the torque spec is higher?

edit: nope, @Pressureangle is correct, below: 8mm x 1.25, torque = 25-30 Nm, tighten in steps back and forth until both pinch bolts are tight.

[Pressureangle]

2 hours ago, nuevototem said:

Hi all,

Just an update from my side. I take my tool and check that both bolts are tight at 25nm and they are ok. There is still play but leave it like that... is ok? do I have to test to tight more nm? like 30nm or 35nm till there is no play? Any suggestions?

I just torqued mine to 34 lbs-ft, which equals 46 nm. 

By the book, an 8mm bolt @ 12.9 tensile torques to 31 lbs-ft or 43nm.  Torque each separately in steps, 25-30-35-40-43 to be sure the yoke isn't twisted more than necessary during the process. 

@docc the bolts are 8mm x 1.25 thread. 

Edited October 26 by Pressureangle

[MotoKnee]

7 hours ago, nuevototem said:

Hi all,

Just an update from my side. I take my tool and check that both bolts are tight at 25nm and they are ok. There is still play but leave it like that... is ok? do I have to test to tight more nm? like 30nm or 35nm till there is no play? Any suggestions?

I had play similar to yours at both ends, the bolts all felt tight, not because they were delivering the desired clamping force, but because the threads were damaged. I suspect you could twist the heads off the bolts and still not eliminate the slop.

I decided to disassemble the whole affair for cleaning, inspection, and proper reassembly. Since I was that deep into it, pulled the swingarm, greased those bearings, greased the evil third zerk, bled the cutch and everything else that easy access presented.

With fresh bolts and correct tightening sequence, all play was eliminated. Splines were clamped tighter than a bull's ass in fly season

 

[Pressureangle]

6 hours ago, docc said:

I thought we had determined the bolts are 10mm and the torque spec is higher?

edit: nope, @Pressureangle is correct, below: 8mm x 1.25, torque = 25-30 Nm, tighten in steps back and forth until both pinch bolts are tight.

The torque I quoted is for 12.9 grade bolts- your lower value is probably for 10 grade or so. FWIW the factory bolts are 12.9 grade. The yokes are quite tough and my replacement bolts have a couple threads out beyond the yoke, so I had no fear torquing them to bolt spec (from memory, obviously I'm a little high at 46nm) 
What is the actual MG service spec for the yoke bolt torque?