I’m busy upgrading and repairing the front and rear end of my 1981 Le Mans III, next job was to be replacing the rear drive main oil seal which is leaking oil onto the back wheel. On removing the rear wheel I have found that the splined coupling of the rear drive that runs in the oil seal can be moved in and out by about 1mm or so, is that normal? I’m guessing it’s not 
.
If as I suspect I have a problem any suggestions on where best to send it for overhaul? I’m okay with engines and gearboxes but that rear drive is a little beyond my area of expertise. Any suggestions or advice will be most gratefully received
Cheers, Don.
Can’t visualise what you’re describing Don, but dependent on where your are, Nigel at NBS is a specialist in transmission issues. Details here
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Hi banquo,
I should have explained myself a bit better, the actual drive flange that protrudes through the main seal, in other words the female spline of the rear drive into which the male spline on the back wheel fits into. On removing the rear wheel I found that if I put my fingers into the drive flange I was able to move the drive flange in and out of the seal/case about 1mm, I could pull the flange out a bit then push it in about 1mm quite easily. It doesn’t feel right to me, but then again maybe the “play” is supposed to be there?
No doesn’t seem right, should be captive in its bearing (behind the seal), or at least reasonably so. When I took mine apart (this would be around 2011 -ish) it wasn’t very tight in the bearing, I replaced it with Loctite. In your case also suggests gear wear! 
I’ve searched the web and YouTube looking for information on the rear drive box but there’s very little precise information available, I did manage to find a single video that seems to suggest the movement on my drive flange is correct, but it doesn’t say how much movement is okay and how much is to much. Dyfer Moto Guzzi - YouTube
The bike is a 1981 model and I’ve owned it since 1986, the seals have never been changed and the box never opened since I purchased it in 1986 and I suspect it wasn’t opened before I purchased the bike, so I guess it’s probably a sensible thing to do to have it opened, inspected and all the seals changed.
The following is a web page I compiled some years ago, and is based on the factory workshop manual –
Moto Guzzi Final Drive Box Overhaul
Note, listed under ‘Faults’, is the line: ‘Lateral play in the crown wheel/output shaft may be felt by pulling and pushing the shaft’
In other words such play is not acceptable. It should be a press fit in the bearing.
Hi Mike, thanks for the information, I have decided to send the drive to NBS and let them strip and inspect it, I’ve been told Nigel from NBS is a top guy who knows his stuff better than most. 
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That would be a good plan! I approve. 
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