Possible u joint, possible something else

[strawbobrob]

Question for you--I'm on the freeway doing 70mph and I start to get a vibration through the bike.  I think it's a rough part of the freeway but it stays that way for about a mile.  Suddenly it gets much worse for about 3 seconds and then comes the mechanical metallic noise of something wrong, clackety clackety clack and a lot of vibration.  I pull over and get a tow home.    Coming off the tow truck, I drive the bike into my garage at very low speed, but no clunkiness--very smooth and no noise at all.  I put it up on the lift and the tires rotate freely.  101k miles.  I know several of you have lost your u joint. Does this description fit what you experienced? Does anyone believe its the transmission, which has been pretty clunky for the past 10 or 20,000 miles, or the final drive?  The tranny will pop out of 2nd if I don't shove it in hard, and neutral is getting vague and once in a while a gear gets popped around in there when I'm in neutral.

[GOOSE]

PULL THE WHEEL .... PULL THE FINAL DRIVE  .... CHECK THE PINION CUP, AND DRIVESHAFT .... I HAD ONE OF MY VALKS HAVE A BAD PINIONCUP/DRIVE SHAFT FOR LACK OF GREASE.

[strawbobrob]

Thanks.  I'll post back when I've done that.

[strawbobrob]

Hey Goose, I've searched back and read that the pinion cup has two holes in the back that need to remain clear because the gear oil in the pumpkin flows into and out of the cup to lubricate it.  Is that right?  One of the holes was clear, one was not.  I had lubed the cup and gear with Maxima blue waterproof low friction high temperature grease about 5000 miles ago.

When I pulled the driveshaft out of the cup, it looked like mud in there--it wasn't dry but the color was adobe.  So I drained the pumpkin and the gear oil was the same color and sort of opaque.  There's no play in the pumpkin itself, not a 1/16th or 1/32 or 1/64 as far as I can tell, and the pinion gear and cup doesn't seem to have any slop. 

So I'll pull the u joint per Rattlebar instructions to check that out.  I hope that's it since I already have a brand new one.  Any thoughts on the mud color in the pinion cup grease and pumpkin gear oil would be appreciated.

[strawbobrob]

Yay, it was the u joint.  Why would anyone pull the swingarm to get to it--rattlebar's instructions were very straightforward.  If anyone has thoughts on what I found in the pinion cup I'd be interested before I put it back together.

[Michvalk]

The grease just mixed with the lube from the rear, causing the color change. Should do that, if everything is working right. The splines need a small amount of grease, along with the fog of lube from the rear end. So to wrap up, you did it right in the first place.

[Disco]

What you describe sounds almost exactly like what mine did when the u-joint grenaded up until the part that you could still ride your bike at slow speeds with no noise or clunkiness, that is.  Mine came out in two pieces.  Yours might still be in one piece, or the yokes aren't bent as far as mine were and they remain "locked up" under light load. 

If it's only the u-joint, it's an easy repair once you have the replacement in hand and the final drive pulled.

[saddlesore]

Yay, it was the u joint.  Why would anyone pull the swingarm to get to it--rattlebar's instructions were very straightforward.  If anyone has thoughts on what I found in the pinion cup I'd be interested before I put it back together.

A month ago my drive shaft disengaged from the pumpkin and was driven into the u-joint. It was stuck so bad I had to pull the swing arm out to pull the shaft and u-joint forward to get it out.
14 years and 105,000 miles it didn't hurt to lube the swing arm bearings too.