Grinding noise coming from shaft drive (Maybe from the UJ end of shaft)

1984 XJ 750 MAXIM U.K.

The problem started after a puncture in the rear on my way home from work ! Not having break down cover I chose to ride it home very slowly (around 10 miles). It was a bumpy ride home as the rear tyre was struggling to stay on.

While fitting the wheel with a new tyre I noticed when spinning the rear wheel by hand a grinding sound that wasn't there before I got the puncture. I took the bike for a short ride and all seemed well. A few days later I took it for a longer ride and 70 miles away from home a terrible vibration started through the whole bike (especially the handlebars), and a short time later the universal joint exploded. Bollox !!!!

I guessed at the time that the unnatural movement in the UJ caused by the bumpy flat was to blame for the UJ giving up !

I just fitted a new UJ and I can still hear the grinding sound previously mentioned. It's a fairly new (second hand) and in good condition shaft and diff since shortly before any of these problems started. And the grinding sound, as far as I can tell, appears to be coming from the UJ end of the shaft, or even from the engine. I should also mention the clutch slips and needs replacing !

I suspect that something else has been damaged that caused the UJ to explode rather than the UJ itself.

Can anyone help please as I don't really know whats going on here or what to do next to fix the issue.

 

When you put a new tyre on did you verify that the bearings were still good?

 

^^^^+1 Bearings

 

The rear wheel bearings seem good, no play in the wheel. the grinding sound is much worse that just bearing's too I think. I used a screwdriver as a stethoscope and placed it on the final drive housing and the output drive. Sounds like the noise is coming from the output drive to me. I know how big the job is to replace the output shaft and the middle gear so its my worst fear that this maybe the problem. But I find it incredibly difficult to believe a flat tyre can cause me to have to split the gear box ! The engine has a genuine 23k miles too. Your comments have been noted and I will investigate the wheel bearings further.

 

You have a very strange situation , for the most part the Diff and the shaft are virtually maintenance free , the shaft is not rubbing on the housing ? or maybe problem is in Diff ? just throwing it out there.

 

When the swing arm was out to replace the universal joint I completely removed the diff and the shaft. I checked by turning the shaft by hand and the diff was turning smoothly. I didnt check if the shaft was rubbing the swing arm so that could be a possible reason. I'll check that too.

 

It could be possible that when the UJ exploded it damage the output shaft then and not before with the puncture. I was doing 70mph when the UJ gave up !

 

Are the brake shoes in good condition and properly adjusted?
Not before, but now; right at this moment.

 

Then all future discussions should be centered around the question "Why am I still alive?".........

 

k-moe good idea, when I take the back end apart again I'll inspect the rear brake too !

chacal, I know right. It was a bad day breaking down 70 miles from home but somebody definitely had my back that day too !

 

I suggest that your new uni joint has a bit of a noise to it also. I have personally had a crunchy uni-joint that I replaced and now put so much grease in with my uni-joint its just... not green.
I soaked that uni-joint in engine oil and then packed it as well as i could after loosening it up, with grease, and it worked and sounded good.
The drive system is so bullet proof compared to a chain that it is hard to imagine a catastrophic failure if you keep an eye on it.
I need a badge on my jacket that says 'Shaft Drive FTW!'.

 

Ok peeps I spent Sunday just gone sorting this problem out. Found the problem in the first minute and kudos to Jetfixer. Thank you Jetfixer .

The UJ is indeed rubbing on the swing arm. My XJ is a custom build ! I put new rear shocks on the bike 8 months ago ( 12.5 inches eye to eye ). The top mounting mounting lugs for the shocks on the frame are custom too ! I believe the new shocks which are the correct (factory) length, are nevertheless too long because of the said mounting lugs. Alas the old shocks were binned and I didn't measure them !

It only rubs when the bike is on a scissor jack with the rear wheel of the ground, it doesn't rub with the wheel on the ground and me sat on it.

The tolerance between the length of the shock and mounting lug combined, and the UJ rubbing the swing arm is clearly to close now.

So I have three choices, buy new shock, get the mounting lugs cut off and shortened or slice a thin slither off the bottom half of the UJ end of the swing arm/shaft housing.

What are you're thoughts on the later because that would be the cheapest and easiest option ( I don't have and can't weld).