My 1981 V50 III has recently developed a loud clanking noise from the rear wheel area, not sure if it is drive box or uni joint. The bike has done a genuine 40k miles and oil is at the correct level. I have removed the rear wheel and there is no play present on the disc but the drive box seems stiff to turn. Can I remove the drive box by simply undoing the 4 ‘acorn’ nuts and sliding it off? Any ideas gratefully received, thanks. John Porter
I confess to not knowing much about V50s other than what I’ve read, but possibly the stiffness is normal, you are trying to turn it just with the disc as leverage. Can you recreate the noise with wheel back on, on the mainstand in gear and turn the wheel backwards and forwards against engine resistance? I assume you’ve deduced it’s drive related not suspension etc.
Thanks for reply Mike. The clanking noise is present when run in top on the stand. I have removed the drive box and drive shaft and think the source of the noise is the universal joint. I have taken it to our local prop shaft specialist and he has pronounced it to be well and truly knackered, he is checking to see if he can source the bearings to repair it. Guzzibits have quoted about £220 for a new one but many weeks delivery as Italy shuts for August.
As for resistance to rotation on the drive box it seems less with it off the machine and as you say there is not much leverage when turning the disc and you are turning a 1:3.8 increase when turning it backwards. The Guzzi manual says ‘if the job is done properly there should be a little damping on the cardan shaft’. Not sure what that means!
Looks like reassembly will be a tricky job with having to keep the shaft pressed in to keep the spring in place while positioning the u j on the gearbox output shaft. Anybody any ideas on this please?
£220! 
Tho I’m well out of date I’m sure - last time I bought a big block one was 30 years ago and £22 if memory serves. 
£220 eek, I remember having a problem with it was either a v35ll or a v65c universal joint there was a place that sold universal bearings along the team valley trading estate towards the South end of the estate L got one from them for about £20 and repaired my drive shaft its still going strong.
I will try and find the receipt scan it and post it back on here it might take a day or so.
Just realised £220 would probably be for a complete new shaft Gutsibits l have always found to be reasonable in their pricing.
TLM have complete shaft for 199 euro.
https://shop.tlm.nl/en/u-joint-v50-3-monza-265mm-12-t-193280210000-moto-guzzi
Prob have to add VAT.
Steve
Found it quicker than l thought
As I suspected is a complete unit
Hi,
When I rebuilt my V50 3 the original shaft was so far gone I had to get a new shaft. The sides of the housing was damaged. If you can find a UJ it’s a job you can do yourself.
Steve.
Hi, Many thanks to those who replied with ideas for repairing or replacing the drive shaft on my V50 3. I have found a local prop shaft specialist (PropTech at Hartlebury) who will repair it next week. Any tips on replacing the swinging arm assembly while keeping the internal spring compressed? Thanks, John Porter
Hi John,
Glad you found a local repair shop. I don’t remember (but it was over a month ago lol) any problems when I put mine together. I think the swinging arm was refitted complete with the shaft and final drive.
I put some decent grease on the splines and that kept the spring in place.
Steve.
On the V50 reassembly is real easy. You can put the drive box back onto the arm with the shaft and offer the whole lot up to the back of the gear box without problems. The spring and ball will be just fine. It is the big twins that I find a complete pita.
Thanks for replies on replacing the swinging arm assembly on my V50 - 3. It was easier than I feared although definitely a two person job. U/J repaired by PropTech at Hartlebury (01299 251247), fast friendly service and charged £50.40 (inc VAT) for replacing the bearings and cross piece thingy. Good service I thought. Thanks again for all replies on this topic, I no longer clank!
All the best, John Porter